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Maristar Toy
07-11-2008, 12:57 AM
I have a 351 w/carb on a Maristar. 330 hours. I've owned it 7 years and it's been great up to now. Boat starts up easily and idles. If I give it full throttle out of the hole, it will not take off: it sputters and runs rough. This happens warm or cold. If I plane the boat out slowly, then give it full throttle it takes off and sounds great.

The boat ran fine last year. This problem started new this year. I took it out first time and noticed problem. There was no water in the water fuel separator (I replaced it with the in-line filter too). The screens in the carb were perfectly clean. I cleaned the flame arrestor too. I changed the spark plugs before taking it out the first time this year. One plug did not have any engine fogging oil residue from winterization; the remaining 7 plugs were all oily from winterization. No remedy has worked. The marina has worked on it all week and cannot fix it: they say the ignition checks out ok and see nothing wrong with carb. I burned 13 gallons of new gas this year. I had the tank a little low at winterization with stabilizer.

As a maintenance item, last summer I cleaned the gas tank, and I took out the screen in the tank pickup. I also removed the anti-syphon valve at the tank.

Any ideas?

skibtlvr4evr
07-11-2008, 01:13 AM
I had a problem with the vent on the gas cap. The rubber had expanded (alcohol in gas) and boat would be starving for fuel. I took cap apart and cut rubber back and no problems since. Good luck

denverd1
07-11-2008, 11:34 AM
"If I plane the boat out slowly, then give it full throttle it takes off and sounds great."
could be a float problem in the carb.

Does is run fine at high RPM? If so, that would rule out fuel starvation.

flipper
07-11-2008, 12:14 PM
Sounds like a carb problem to me.

JimN
07-11-2008, 12:16 PM
Did it overheat recently? The fact that it didn't have any fogging oil tells me that it may not have good compression in one cylinder and if it's bad enough, it won't be drawing fuel in, either. One boat I worked on had new head and intake manifold gaskets with Permatex Ultra Copper sealant on them, which is a big problem. He overheated it, the sealant basically melted and the compression caused a leak between cylinders. Eventually, the head gasket eroded to the point that 1-1/2" was missing and while it idled great, it was really lumpy under load.

I think they need to look into why no fogging oil got on the one plug.

"As a maintenance item, last summer I cleaned the gas tank, and I took out the screen in the tank pickup. I also removed the anti-syphon valve at the tank."

You took the screen out and cleaned it or just removed it? I wouldn't recommend that, or removing the anti-siphon.

83hurstguy
07-11-2008, 01:35 PM
Check the accelerator pump in the carb. WITHOUT the motor running, watch the accel pump squirters on the primary side and have somebody pump the throttle. Make sure you are getting a good solid stream of fuel from the squirter.

Make sure the springs in your distributor for the spark advance aren't broken.

JimN
07-11-2008, 01:43 PM
Or, remove the throttle cable and pump it manually.

I'd like to know more about the history of the boat, as far as other engine problems. The unfogged cylinder is intriguing. Was it #1? Maybe it could have used more fogging oil and that's all but if the others were all well coated,....

Maristar Toy
07-11-2008, 02:36 PM
It did overheat 3 summers ago when pump and thermostat went bad. I had it checked out at a Marina directly afterwards. They said no damage had been done. Plus it ran good last summer. The 'dry' plug was on driver side and it was one of the 2 middle cylinders. The Marina did a compression test this week and said it was ok.

Maristar Toy
07-11-2008, 02:37 PM
Yeah, once the boat is planed out and you give it full throttle, it takes off.

Thanks, Greg

Maristar Toy
07-11-2008, 02:47 PM
With engine off, I did verify fuel squirts in carb. I will advise mechanic about springs. Thanks.

JimN
07-11-2008, 03:08 PM
Ask if they did the compression test with all plugs removed. If cylinders 2 and 3 lost the gasket between them, it sounds like the same symptom as the one I worked on. Unfortunately, it may have checked out OK immediately after the overheat but subsequent running may have caused the current problem.

How old are the plug wires?

Maristar Toy
07-11-2008, 04:15 PM
Ask if they did the compression test with all plugs removed. If cylinders 2 and 3 lost the gasket between them, it sounds like the same symptom as the one I worked on. Unfortunately, it may have checked out OK immediately after the overheat but subsequent running may have caused the current problem.

How old are the plug wires?
Jim,

I've put about 220 hours on current wires over a period of 7 years. The engine has 330 total hours. I don't know if they are original or if they were replaced before I bought it. They're probably original since I bought it with 110 hours and 8 years old.

GuitsBoy
07-11-2008, 05:48 PM
Jim,

I've put about 220 hours on current wires over a period of 7 years. The engine has 330 total hours. I don't know if they are original or if they were replaced before I bought it. They're probably original since I bought it with 110 hours and 8 years old.

Even without too many hours, at 7+ years, those wires may be suspect... Might as well invest in some new ones.

JimN
07-11-2008, 07:06 PM
Wires get wet, the insulation stops insulating and then crossfire happens. I would definitely replace them when they're this old. There's no guarantee that this is the problem but they are awfully old.

Maristar Toy
07-11-2008, 07:35 PM
Wires get wet, the insulation stops insulating and then crossfire happens. I would definitely replace them when they're this old. There's no guarantee that this is the problem but they are awfully old.
Sounds good. I will replace wires. Thanks, Jim.

JimN
07-11-2008, 08:04 PM
How old did you say the cap, rotor and plugs are?

Maristar Toy
07-12-2008, 02:01 PM
The cap and rotor are the same as the wires. The plugs are brand new.

JimN
07-12-2008, 03:37 PM
Look under the cap and see if the posts are all fuzzed up (that's the technical term). I use a wire brush to clean them and it can be done in place, without removing the wires, although bending the wires can cause problems with the silicon in the middle. It tends to solidify over time with high voltage going through and once it cracks, it's not good. If you look inside the cap and see dark lines from one post to another, replace it. This typically means that it's arcing and you may never see it from the outside.
Have you run it when it's dark? If you rev it up and see arcing, it's definitely time to replace the wires.

If you have a multi-meter, you can check for continuity in the wires.

I usually have issues with my truck when a cap/rotor are more than a few years old. If it runs well, I see no reason to replace every year but if it runs hard and a lot, plugs go and I check out the rest. Plug wires only last a few years before they lose their ability to insulate.

Maristar Toy
07-12-2008, 11:46 PM
Jim,

Replacing the cap and rotor fixed it. I will do the wires too. The shop says replacing the ignition module is the next course of action if it behaves like this again. Thanks for all of your help! You diagnosed it better over the internet than the hands-on guys.

jprocto3
07-15-2008, 12:55 AM
We had a similar problem with our 93 maristar. We replace the marine carb with a standard automotive carb. Eventually we put another holly marine carb back on the motor and haven't had anymore problems.

Maristar Toy
07-25-2008, 12:36 AM
The engine is failing again. I took the boat on vacation last week. I put about 6 hours into testing it fine. Then it started the same problem again. The plugs, cap, rotor, and wires are brand new. I pulled 2 plugs for a test and they were not fouled. The marina said the next part to replace would be the electronic ignition (is there a way to test this?). Hole shots are terrible with misfires (hot or cold engine). Again if, the boat is planed out about 2400 rpms and above, I can give it WOT with no misfires. On one occasion, the boat did not start while hot. I let it sit for 15 minutes and it started up again. Any ideas.

Storm861triple
07-25-2008, 01:47 PM
On one occasion, the boat did not start while hot. I let it sit for 15 minutes and it started up again. Any ideas.
In that case the boat is giving you a great opportunity to figure out the root of the problem. When it won't start, does it have spark? If not, then you can pretty much assume that it's the pick up coil (electronic ignition),, since you changed everything else in the seconday ignition system except the ignition coil (which RARELY fails). If it DOES have spark, then you obviously have a fuel issue; either flooding or starving. You need to determine if it's spark or fuel before we can really help you beyond that.

marina said the next part to replace would be the electronic ignition (is there a way to test this?).
Yes. You should be able to put a test light on the wire running to the coil's ground side and connect the test light lead, to ground. While cranking the engine you should see the light flash on and off for each firing pulse; 4 per crank revolution. If this doesn't happen, then your pick up coil isn't functioning. Of course, if the engine is running, your test will show that everything is fine....because under those conditions, at that time, everything is "fine". You need to run this test when it son't start and you've verified that it's spark related, OR during a WOT acceleration attempt, w/the engine cover off, a driver, and a well braced person running the test. It that case, you be looking for an erratci lighting of the test light that coencides with the misfiring. This test would be tough to monitor though, IMO.

IMO, it SOUNDS spark related, but testing for spark when it won't start will be much more definitive.

Maristar Toy
07-28-2008, 12:15 AM
At the suggestion of JimN, I found 2 faulty plugs that were brand new. The marina mechanic over torqued them. One insulator could be rotated freely due to the overtightness. I put 2 new plugs in and it ran great.

Thanks for feedback everyone.

JimN
07-28-2008, 09:55 AM
One thing I found when I worked on these is that, because of the shape of the exhaust manifolds, using a socket for the spark plugs isn't usually the best thing for the plugs. The chance of breaking the ceramic is pretty good, so I started using a 5/8" box wrench to loosen them and then an old ploug wire with the boot to remove them.

bigmac
07-28-2008, 10:05 AM
Jim,

.....

You diagnosed it better over the internet than the hands-on guys.

Yeh, that's not uncommon in the three years I've been reading this board. Although he's apparently no longer a boat service tech, he still fixes boats here on almost a daily basis.

rob935
07-28-2008, 03:46 PM
i would have thought it was a carb problem but glad you have it sorted , ive broken a few plugs too in the past and dont use a plug wrench any more for that reason ..

Zalamander
07-29-2008, 03:53 PM
I had the same problem. I replaced the carb and did a full tune-up, and still had problem. Turned out to be mechanical advance in distributor. Converting to electronic Ignition now ($180).
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