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GuitsBoy
08-03-2010, 02:24 PM
OK, So Im slowly getting through all the issues with my boat. I still feel like I have some performance problems with it. With the empty boat and stock prop, Im still only seeing about 36 MPH at 4400 RPM. Im thinking it should be closer to 42 MPH at 4600 RPM, especially with the 285 HP motor. Also, I have some off idle hesitation when I pull someone out of the water.

I have replaced the following in the last year:

New Plugs, Wires, Cap and Rotor
New Coil
New Electronic Ignition Pickup
Rebuilt Holley 4160

The fuel ump does not show any fuel in the indicator tube. The secondaries are opening up just over 3K RPM. I dont feel any odd vibrations that would indicate a propshaft or prop issue. Im starting to think it might be timing related. When I replaced teh ignition pickup, I noticed that there was a lot of rust all over teh centrifugal springs. I dont have a timing light, but I might pick one up the next time I take the trip up to the boat. Does teh motor have timing markings on the damper or no? I dont recall seeing them, but I wasnt looking either....

flipper
08-03-2010, 02:50 PM
Yes, they are there. Make sure it is advancing all the way too. I had the same problem to find out the springs were bad and it wasn't advancing all the way like it should. May be worth replacing them just to check that off the list

GuitsBoy
08-03-2010, 04:29 PM
Yes, they are there. Make sure it is advancing all the way too. I had the same problem to find out the springs were bad and it wasn't advancing all the way like it should. May be worth replacing them just to check that off the list

I would love to replace them, but I havnt tracked them down yet. I sent an email to the guys at skidim, and am awaiting a reply. Has anybody found another source for them?

Also, I should be looking for 10* BTDC at idle, and 20* by ~3K or so?

Thanks for the info...

GuitsBoy
08-03-2010, 06:15 PM
I should also state that the rebuild kit I used was the Holley 703-47 kit, which lists carb number R80319-1, which I believe is the preferred marine 4160 model. I would assume that the power valve would be the correct one, no? If not, this could be the cause of my off idle hesitation.

jconover
08-03-2010, 06:25 PM
Power valve should be a 2.5 on a 600 CFM 4160. Unless it is leaking due to backfire, the power valve shouldn't be causing hesitation at idle. The power valve opens up to provide additional fuel during acceleration transition. The "2.5" means it opens when the vacuum pressure in your engine reaches 2.5... Most engines have about 12.5 inches of vacuum at idle and produce steadily less vacuum as the throttle is increased.

You can test whether your power valve is leaking or not by turning your idle mix screws all the way in. The engine should die. If it does not die, your power valve is leaking. (Make sure you count how many turns in it takes to get your idle needle to seat so that you can restore it to the previous position later.. .you might post this information too)

Timing issues can also cause hesitation, but let's start with the fuel system first and see if you're getting all the right behavior there.

It sounds more to me like the engine is starving for fuel (e.g. it is too lean) - I would check your accelerator pump squirters to make sure they are dumping fuel in when you give throttle (you can do this with the engine off - look down the primaries and fully depress the throttle, you should see the squirter sending fuel in). If that is OK, double check your idle circuit screws.

Oh yeah, and yes, 10 degrees advanced (10 BTDC) is proper idle timing at 1000 RPM. As far as full advance, I get 32 degrees of advance on my engine at 3K RPM, but I don't have the same engine. I don't see you actually list which 285 HP motor you have.

GuitsBoy
08-03-2010, 06:40 PM
Power valve should be a 2.5 on a 600 CFM 4160. Unless it is leaking due to backfire, the power valve shouldn't be causing hesitation at idle. The power valve opens up to provide additional fuel during acceleration transition. The "2.5" means it opens when the vacuum pressure in your engine reaches 2.5... Most engines have about 12.5 inches of vacuum at idle and produce steadily less vacuum as the throttle is increased.

You can test whether your power valve is leaking or not by turning your idle mix screws all the way in. The engine should die. If it does not die, your power valve is leaking. (Make sure you count how many turns in it takes to get your idle needle to seat so that you can restore it to the previous position later.. .you might post this information too)

Timing issues can also cause hesitation, but let's start with the fuel system first and see if you're getting all the right behavior there.

It sounds more to me like the engine is starving for fuel (e.g. it is too lean) - I would check your accelerator pump squirters to make sure they are dumping fuel in when you give throttle (you can do this with the engine off - look down the primaries and fully depress the throttle, you should see the squirter sending fuel in). If that is OK, double check your idle circuit screws.

Oh yeah, and yes, 10 degrees advanced (10 BTDC) is proper idle timing at 1000 RPM. As far as full advance, I get 32 degrees of advance on my engine at 3K RPM, but I don't have the same engine. I don't see you actually list which 285 HP motor you have.

Thanks for the info... The motor in question is an indmar ford 351 HO. Im not really sure they see timing quite that high.

As far as the power valve, its not blown out as the engine has never backfired, and closing the idle circuit screws does indeed kill the motor - I just happened to do that this weekend while trying to dial in the tune. I currently have them about 3.5 turns out. And the PV in my holley renew kit was indeed the 2.5.

As for the accelerator pump, it does indeed squirt into both barrels. I dont know if the accelerator pump cam is set correctly, but I would guess its still at the factory settings. I didnt test by using the throttle, but by gently pressing the pump diaphragm bottom. If I recall, theres an adjustable nut and bolt to set the gap for the pump. I could try and reduce the gap a bit and see if that helps it out of the hole.

Thanks again!

jconover
08-04-2010, 01:22 PM
The nut that adjusts the accelerator pump impulse... turning it one way increases the initial fuel burst while lowering the total volume... turning it the other way decreases the initial burst but increases the total volume.... my holley book talks about why you would do this one way or another, but that's more than i've got time to type out here... i don't know that this is going to fix your problem, if you are getting fuel through the squirters, then that's probably not it. Let's wait and see what other ideas come up for correcting hesitation, I'd hate to start messing with the accelerator pump and just introduce another variable.

GuitsBoy
09-07-2010, 11:11 AM
This past weekend I decided to start playing with the timing. Before making any changes, the timing was set to 9* or 10* BTDC, and went up to about 18* above 2500 RPM.

Upping the base timing a bit immediately cleaned up idle. It seemed to idle best around 20* BTDC, but I feel like running 30* on the top end might be a little too much. I settled on 16* base timing, which cleaned the idle up about 80% better, and results in about 25* above 2500 RPM.

The water was way too choppy this weekend, so I only took her out for a quick test run. The boat is noticeably stronger out of the hole with no more hesitation or bog when you punch it. The top end was difficult to find due to the conditions, but it looks like it'll settle somewhere around 37 or 38 MPH at 4600 RPM. Its better, but still a bit below where it should be MPH wise. Ill verify with GPS on a long stretch next time I am up at the lake with some good conditions.

Anyway, does anyone think Ill have any problem running 16* base timing and 25* on the top end? I shimmed the engine cover open just a crack and repeatedly punched the throttle and didn't hear any pinging. To make matters worse, we only have 87 octane available at the marina, so Im probably pushing my luck. I didn't run the boat enough to bother checking the plugs, but at the previous timing, they read a perfect powdered chocolate color. As long as I don't hear any pinging under load, I should be fine, right?

JLeuck64
09-07-2010, 12:01 PM
Sounds like it is time to clean up the advance weights... Pull the breaker plate off and then remove the weights and clean up all the rust you were talking about. The pivot points might be holding back your ignition advance.

jconover
09-07-2010, 12:06 PM
I agree with JL above. For reference, my engine (454... but it seems timing advance is pretty much similar on 351s/352s) advances to about 32-34 degrees. It really does sound like your weights and springs are either stuck, or possibly a broken/worn out spring, or the wrong springs (if someone replaced them).

Running 16 degrees advanced is pretty far out of spec - I can totally confirm it will make your engine idle better, but your instinct that it might be causing pinging is a good one... remember that just because you can't hear cylinder detonation doesn't mean that some pre-ignition isn't occuring... just not loud enough to cause audible pinging. That said, many "performance junkies" run automobiles advanced to 16 degrees at idle with aggressive cams, so you're not too far into the red zone.

My advice is still to determine what in your ignition is causing the poor idle.

GuitsBoy
09-07-2010, 12:08 PM
Sounds like it is time to clean up the advance weights... Pull the breaker plate off and then remove the weights and clean up all the rust you were talking about. The pivot points might be holding back your ignition advance.

As it turns out, the rust I mentioned was grossly over exaggerated. There was barely any surface rust, and everything was moving freely. The springs and weight pivot bushings were all rust free. I lubed everything up and reassembled. It seems to be working correctly as I see 9 or 10 degrees additional advance between idle and 2.5K RPM.

GuitsBoy
09-07-2010, 12:17 PM
I agree with JL above. For reference, my engine (454... but it seems timing advance is pretty much similar on 351s/352s) advances to about 32-34 degrees. It really does sound like your weights and springs are either stuck, or possibly a broken/worn out spring, or the wrong springs (if someone replaced them).

Running 16 degrees advanced is pretty far out of spec - I can totally confirm it will make your engine idle better, but your instinct that it might be causing pinging is a good one... remember that just because you can't hear cylinder detonation doesn't mean that some pre-ignition isn't occuring... just not loud enough to cause audible pinging. That said, many "performance junkies" run automobiles advanced to 16 degrees at idle with aggressive cams, so you're not too far into the red zone.

My advice is still to determine what in your ignition is causing the poor idle.

So your sating that I should see closer to a 20 degree difference between idle and 3000 rpm? Idle should be 10, and 3K should be 30?

Also, running 16 degrees of timing is probably a lot more acceptable in a hot rod with a big cam with a lot of overlap. We probably need to be a bit more conservative with timing since our cams are smaller and designed to make power lower in the RPM range than a race car would.

Anyway, like I just mentioned, The weights were clean and in good working condition. While I cant guarantee that the weights were not replaced buy the previous owner, I have no reason to believe they were. It looked like there was one heavier spring and one lighter spring. I assume this was to give it a timing curve as opposed to a linear advancement.

jconover
09-07-2010, 03:57 PM
Yes, stating that on my engine, and per all my forum research here including the links back to the manuals for the various model years, 20 degrees advance from idle seems to be approximately right. I know many times in the past East.TX.Skier has posted links to the manuals for the various model years, which including timing advance adjustment. Google finds a reference by JimN indicating that 20 degrees additional advance is what he remembers (he says IIRC) for 351W. This concurs with everything I have read both here and on other forums.

Relevant link here:
http://www.mastercraft.com/teamtalk/showthread.php?t=7745&page=2

Having been through an engine rebuild because my PO was running the timing way too far advanced to correct for bad ignition parts, I can show you first hand what happens to valves when you continually run the timing too far advanced (and we didn't hear any pinging, either). You get valve 'tulip'ing, which ultimately leads to valve burn through or cracking.

My total advance is currently in the range of 34 degrees; I run the engine at 11-12 BTDC because the 454 is just a beast to idle at 10 degrees. the extra 2 degrees give me all the extra energy i need to keep the engine idling smoothly at 740 rpm (out of gear).

GuitsBoy
09-07-2010, 04:14 PM
Thanks for the link, I had already come across it a little earlier. Due to the weather I had been checking the motor at 2.5K RPM in neutral as rather than under load. It was just way too choppy to be keeling over a running engine trying to read the timing. Im guessing that theres probably plenty more advance left in those springs then. I seem to remember reading that full advance was reached by 2500 or so RPM, but I cant find that anymore, so Im guessing this is not the case. Sorry for my incorrect assumption.

Is it possible that the damper may have drifted a few degrees over the years? I haven't pulled a plug and installed a locator yet, but I do know that it was a HUGE pain in the butt to start this motor at 10* base timing, and now it starts like a champ at 16*.

jconover
09-07-2010, 07:10 PM
RE:2500 rpm -- My service manual says to measure full advance at 3K. It says the timing should be fully advanced at 3000 RPM.

I don't fully understand the interaction between the damper and timing advance, if any - so I can't be of much help there.

GuitsBoy
09-07-2010, 07:11 PM
RE:2500 rpm -- My service manual says to measure full advance at 3K. It says the timing should be fully advanced at 3000 RPM.

I don't fully understand the interaction between the damper and timing advance, if any - so I can't be of much help there.

well, the timing marks are on the outer ring of the damper, right? If its starting to delaminate, perhaps the timing marks are no longer accurate. Only way to verify would be to locate TDC manually.

jconover
09-07-2010, 07:22 PM
Oh oh oh! - harmonic balancer - damper plate is between the engine and the transmission.

You can check whether your harmonic balancer is dead on or not. There are two ways - the easier is to pull off the rocker covers and visually inspect the #1 intake valve - the piston needs to be at the top of the intake stroke thus the intake valve will have just opened, and the exhaust valve will have just closed. The harmonic balancer should be at TDC (0 degress) at the top of the stroke. This is somewhat of a PITA since you can't actually see the cylinder coming up, but you can easily see the rocker arms moving and determine whether your timing mark is dead on or not.

You are correct that all of your problems could be related to a slipped harmonic balancer. You can usually tell if it is slipping by trying to turn it with a strap wrench or other. There is some small chance that timing chain jumped a link, too, but I think we talked about that at the beginning of the thread... Odds are against that.

gdlrwr
09-07-2010, 09:20 PM
I had that same type of problem after doing a full tune up. it took awaile but I had a few brand new Spark plug wire that were bad. I was getting a spark but not full power. with a laser temp Gauge I was able to find what cylinders were not fireing. swawped wires and then it heated up. then ordered new wire and problem was fixed

ahhudgins
09-07-2010, 10:29 PM
The water was way too choppy this weekend, so I only took her out for a quick test run. The boat is noticeably stronger out of the hole with no more hesitation or bog when you punch it. The top end was difficult to find due to the conditions, but it looks like it'll settle somewhere around 37 or 38 MPH at 4600 RPM. Its better, but still a bit below where it should be MPH wise. Ill verify with GPS on a long stretch next time I am up at the lake with some good conditions.


I'm not an expert, but it sounds like you are getting the RPMs you need out of the engine, but not enough speed out of the prop or transmission. What prop are you running?

GuitsBoy
09-08-2010, 09:29 AM
I'm not an expert, but it sounds like you are getting the RPMs you need out of the engine, but not enough speed out of the prop or transmission. What prop are you running?

Yeah, I tend to agree. The problem is that my tach only reads 3800 while my perfect pass reads 4400. I tend to believe the perfect pass, but after having an RPM adapter go bad on me, im not sure how accurate those things are either.

Anyway, its the stock prop with the 1:1 transmission. 13x13 four blade. No bad vibrations, no dings, transmission doesn't slip and fluid looks good. Nothing that leads me to believe its a problem with the drivetrain. Thats why the discrepancy between RPM and MPH is now making me question the perfect pass tach.

I should note that I have a second 1" through hull water scoop for the ballast, but I don't think the extra drag from that should impact me by a handful of MPH, should it?

GuitsBoy
09-08-2010, 09:30 AM
I had that same type of problem after doing a full tune up. it took awaile but I had a few brand new Spark plug wire that were bad. I was getting a spark but not full power. with a laser temp Gauge I was able to find what cylinders were not fireing. swawped wires and then it heated up. then ordered new wire and problem was fixed

This is my second set of new wires/plugs/cap+rotor since ive had the boat. No change in performance. But definitely a good idea to check. When I first cammed my car I had two plug wires that werent making a connection. I thought it was just that lumpy a cam, and drove it around that way for a couple days before I figured it out.

ahhudgins
09-08-2010, 10:57 AM
Yeah, I tend to agree. The problem is that my tach only reads 3800 while my perfect pass reads 4400. I tend to believe the perfect pass, but after having an RPM adapter go bad on me, im not sure how accurate those things are either.

Anyway, its the stock prop with the 1:1 transmission. 13x13 four blade. No bad vibrations, no dings, transmission doesn't slip and fluid looks good. Nothing that leads me to believe its a problem with the drivetrain. Thats why the discrepancy between RPM and MPH is now making me question the perfect pass tach.

I should note that I have a second 1" through hull water scoop for the ballast, but I don't think the extra drag from that should impact me by a handful of MPH, should it?

Like you mentioned, I would put a GPS on it and check your MPH before digging any more. I'm getting my wife a GPS and telling her it's for our road trips but it's actually for me to fine tune my speedometer in the boat ;)

GuitsBoy
09-08-2010, 10:59 AM
Like you mentioned, I would put a GPS on it and check your MPH before digging any more. I'm getting my wife a GPS and telling her it's for our road trips but it's actually for me to fine tune my speedometer in the boat ;)

While I didnt have my GPS on the last time we were out, I have dialed in the speedo and perfect pass in the past. Its within a couple MPH. But good advice none the less.

MatthewStokes
09-11-2010, 05:30 PM
GuitsBoy, hi. I've got the same setup and boat minus Perfect Pass, 92 PS 205, 4160, 1:1 transmission and 13 x13 prop. I'm closer to 44 MPH at 4600 rpm. I read someplace and I'm sure there are others here more knowledgeable, that if you are only hitting 36 MPH and 36-3800 RPMs then your secondary isn't opening. Have you verified that the secondary is indeed opening at that speed?
As part of the rebuild did you replace the secondary vacuum diaphram?

GuitsBoy
09-14-2010, 09:44 AM
The secondary is definitely opening. You can feel and hear it open right over 3K RPM. Im still unsure about the RPM. Perfect pass is telling me that we're running at 4400 or better RPM at WOT, but still only at 36 MPH. At least thats where we were at last time I had good water and a GPS.

oldairboater
09-14-2010, 04:14 PM
Boat sounds slow but the rpm sounds right. More pitch would bring down the rpm and add some speed but possibly at the expense of the hole shot. The secondaries are coming it at the right rpm. I would have a talk with the prop guy and get an expert opinion but first I would check my rpm against speed one more time. Good accurate information solves problems--errors in information even innocent compound problems.

Kyle
09-15-2010, 12:47 PM
Yeah, I tend to agree. The problem is that my tach only reads 3800 while my perfect pass reads 4400. I tend to believe the perfect pass, but after having an RPM adapter go bad on me, im not sure how accurate those things are either.

Anyway, its the stock prop with the 1:1 transmission. 13x13 four blade. No bad vibrations, no dings, transmission doesn't slip and fluid looks good. Nothing that leads me to believe its a problem with the drivetrain. Thats why the discrepancy between RPM and MPH is now making me question the perfect pass tach.

I should note that I have a second 1" through hull water scoop for the ballast, but I don't think the extra drag from that should impact me by a handful of MPH, should it?

Do you have a good ground.... Something is making you have 2 different readings in RPM. You sure dont want to over rev. What is the perfect pass speed reading vs the other speedo. If you have a bad ground somewhere then your perfect pass will be crazy. Mine kept re-setting due to the master module being too close to a subwoffer. Just another thought is that if you are turning the perfect pass off to run wot then your speed is read off of the paddle wheel. Is the paddle wheel chipped or damaged at all. I would also see if there was a way to measure ohms or any other test to do on the paddle wheel to see if it is good.

I may even go buy a tach and hook it up to the coil and just make sure and exact what you are getting. Personally I would figure out rpm first so you dont over rev and hurt the engine. Then I would return the tach cause you dont need it any more.

I would also have someone drive the boat and look in the secondary of the carb and see if you are getting a good fuel spray. Take the motor box out and flame arrestor off and go open her up. I have seen them open but just start running lean due to not enough fuel. Since you keep replacing plugs you probably have not run it lean enough to mark the plugs so you could see.

You may have tried some of these things but this is what I was thinking when I was reading about what else is left to do.

jconover
09-15-2010, 02:02 PM
Sears digital timing light has a built in tach and advance meter all in one. very nice. Was $79 on sale, $99 regularly. bought one a few weeks ago.

Cloaked
09-15-2010, 02:49 PM
The secondary is definitely opening. You can feel and hear it open right over 3K RPM. Im still unsure about the RPM. Perfect pass is telling me that we're running at 4400 or better RPM at WOT, but still only at 36 MPH. At least thats where we were at last time I had good water and a GPS.With a 1:1 ratio, you can be fairly confident that (if the speed-o is correct) that the speed and the RPM should be about the same reading. Just a ballpark gauge for your last question of PP vs. tach.

GuitsBoy
09-15-2010, 04:02 PM
Speedo accuracy is within a MPH or two as verified via GPS. Tach accuracy has not been verified. I suspect perfect pass is pretty close though, since its redlining at 4500 or so with the stock prop as the only rev limiter. She runs plenty strong, but the top speed just doesnt seem to be there. Very strange. I can only reasonably believe its a problem with the prop or shaft at this point.

ahhudgins
09-15-2010, 05:25 PM
If it were me I would want to be 100% on my RPMs since you've checked the speed with the GPS. You have the factory tach reading one thing and the perfect pass reading another. I would buy another test tach. If you are indeed turning 4400 RPMs then your problem is behind the crankshaft.

Kyle
09-16-2010, 12:00 AM
If it were me I would want to be 100% on my RPMs since you've checked the speed with the GPS. You have the factory tach reading one thing and the perfect pass reading another. I would buy another test tach. If you are indeed turning 4400 RPMs then your problem is behind the crankshaft.

Very well put.