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View Full Version : 94 PS EFI Bogging down


sdesmond
05-26-2008, 04:30 PM
Saturday we took the boat on the maiden voyage of the season and all was well. All through the powerband the boat was tops. We started with a 3/4 tank of gas. Sunday we went out again and all seemed fine. Boat starts fine and we take it off the lift and it runs good. Accelerates hard and all is well. We cruised probably around 2000 to 2500 rpm most of the trip. On the way home I went to get on it and when I pushed the throttle down it bogged and the pitch of the engine changed like it is starving for fuel. When I let up on the throttle a bit it ran fine at about 4000 rpm. The longer we drove this it seemed to get worse and anything over 3000 rpm would bog it down. This morning I pulled the fuel pump to look at it and everything was fine. No debries at the bottom of the pick up or anything like that. I put a brand new fuel filter on and went to give it a try. Got it off the lift and it ran fine again. 4200 rpm was hit and acceleration was fine. I then figured the fuel filter was the culprate and it was all fine. We went for our ride and at about 2000 to 2500 rpm. About 1 hr later i decided to get on it and same thing. It fell on its face. I brought the boat to a stop and decided to mash the throttle and it was slow accelerating. Wont even pull up a skier. What would the next thing be to check? It has the fuel tank cleaned last season to remove the debries that was in it. There was some carpet scraps and crapin it. It had a new ignition module installed last season. I am back home from the lake place and I will not get to it till this coming saturday. I just pulled my Indmar Shop Manual and it says it could be gas tank ventilation. I will look in to that next time I am with the boat. If there is anything else somebody can thing of I would really appreciate it. Thanks! I may also add it is TBI.

chico
05-26-2008, 05:41 PM
It could be going into limp home mode.Anyway to check for error codes?Fuel pressure?

sdesmond
05-26-2008, 08:27 PM
How would I check that? There is a MC dealer on my lake. I would rather do it myself if I can instead of paying..

rholmes
05-27-2008, 12:28 AM
The only other thing I can think of is vapor lock from heat soak.
To the idea of gas tank ventilation, did you check the vent line to make sure it was clear? A bug or something of the sorts could have made a home in it a jammed it up (not likely as they probably don't like the fumes, but still possible). Next time you are out, you can unscrew the gas cap on the tank about halfway to see if the pressure is allowed to equalize and solve the potential problem.

JimN
05-27-2008, 07:44 AM
Vapor lock doesn't happen often when you have fuel pressure in the range of these motors. Much easier with a mechanical pump and a carb. However, running the blower or opening the motor box when it's hot is a good thing to try.

Did it run smoothly when it was bogging, or was it lumpy? If it registered an overheat, heat soak is a possibility but should have been resolved when the temperature dropped.

Did you check the impeller? How dirty is your flame arrestor? Make sure the oil cooler is clear of any blockage.

Re: codes- if you know the GM paper clip method, it works on these, too.

Read some of the recent threads here regarding loss of power, fuel pressure, etc. Some of the recent ones deal with the same thing and generally, all of the recommendations apply when there's a performance issue.

sdesmond
05-27-2008, 07:55 AM
Vapor lock doesn't happen often when you have fuel pressure in the range of these motors. Much easier with a mechanical pump and a carb. However, running the blower or opening the motor box when it's hot is a good thing to try.

Did it run smoothly when it was bogging, or was it lumpy? If it registered an overheat, heat soak is a possibility but should have been resolved when the temperature dropped.

Did you check the impeller? How dirty is your flame arrestor? Make sure the oil cooler is clear of any blockage.

Re: codes- if you know the GM paper clip method, it works on these, too.

Read some of the recent threads here regarding loss of power, fuel pressure, etc. Some of the recent ones deal with the same thing and generally, all of the recommendations apply when there's a performance issue.


The motor ran smoothly when it was bogging down. The pitch of the motor changed a bit and you can hear it straining for something. When i let the throttle back up it was fine. I did remove the flame arrestor and all was fine with it. Also my temp gauge states that the motor is only getting up to about 140 or so.

NatesGr8
05-27-2008, 08:05 AM
Is there any chance that your transmission could be slipping? My xmission has been going and if the fluid is low and i try to get on it, it sounds alot like what you're describing is going on with yours.

JimN
05-27-2008, 08:31 AM
If the transmission was slipping, the motor would rev too high.

Does the exhaust smell strongly of gas? If it does, it could be too rich from the motor running too cold. 140 is low. Did you look at the thermostat?

sdesmond
05-27-2008, 08:37 AM
That was replaced last year so I did not look at it. I guess I shouldnt assume just because it was changed its good. I will pull it and look at it. I didnt check the exhaust smell.

JimN
05-27-2008, 08:47 AM
Make sure the thermostat is rated for 160 degrees. Anything lower will just waste gas. Also, if you don't keep the boat in the water, look into the exhaust ports to see if there's any kind of blockage.

sdesmond
05-27-2008, 08:52 AM
I keep it on a lift so I can check the exhaust. The thing that urks me the most is the day before none of this was going on and it ran great.

sdesmond
05-27-2008, 11:21 AM
Also, even after running the boat hard I dont think the temp has ever moved past 140-145.

JimN
05-27-2008, 12:45 PM
How long have you owned it? Unless the water temp is really low, like early spring in a large lake where it takes until the end of the season to warm up, it shouldn't read that low, except when passing it to go to normal operating temperature. I would look for obstructions in the raw water system and if you still have a petcock in the block (the side that doesn't have the knock sensor), change that to a brass plug, even if a heater gets its hot water supply from a T fitting.

I would also find out if it has any stored codes.

My concerns at this point are:
Fuel pressure and quality (look in the tank for a clear, gelatinous mass) or loose dirt in the chamber with the pickup tube)
Raw water supply and any blockage in the exhaust manifolds or risers, This can be rust scale, dirt/silt or impeller vanes from a previously destroyed one.
Bad/missing/clogged thermostat
Heat soak without running the blower after sitting- this should be done before starting, just like if it has been idle for a week. You can also open the motor cover,

Generally, if a motor can't go past 3K RPM under load, it's a fuel delivery issue and that's usually a clogged filter or screen. I would look at the screen again.

sdesmond
05-27-2008, 01:56 PM
How long have you owned it? Unless the water temp is really low, like early spring in a large lake where it takes until the end of the season to warm up, it shouldn't read that low, except when passing it to go to normal operating temperature. I would look for obstructions in the raw water system and if you still have a petcock in the block (the side that doesn't have the knock sensor), change that to a brass plug, even if a heater gets its hot water supply from a T fitting.

I would also find out if it has any stored codes.

My concerns at this point are:
Fuel pressure and quality (look in the tank for a clear, gelatinous mass) or loose dirt in the chamber with the pickup tube)
Raw water supply and any blockage in the exhaust manifolds or risers, This can be rust scale, dirt/silt or impeller vanes from a previously destroyed one.
Bad/missing/clogged thermostat
Heat soak without running the blower after sitting- this should be done before starting, just like if it has been idle for a week. You can also open the motor cover,

Generally, if a motor can't go past 3K RPM under load, it's a fuel delivery issue and that's usually a clogged filter or screen. I would look at the screen again.


I bought this boat from my cousin in october. He put about 2k in to it before I got it. They pulled the gas tank and cleaned it because he had the problem of carpet fibers in there. Also, I guess I didnt state that there is no screen at the bottom of the fuel pickup. It is just a black cone at the bottom of the pickup tube. The raw water pump was replaced along with the thermostat when it was in there along with some other stuff that I dont remember off the top of my head. The work order is at home. Like I stated though when I pull it off the lift it runs fine. It is just after it as been running for a bit this happend. I guess I will have to wait till friday evening and Ill dig in to it again. I may drain the tank and put all new gas in it as well.

JimN
05-27-2008, 03:02 PM
I was referring to a screen at the pump inlet. Fibers get past the fuel pickup and collect at the pump inlet screen, and it sounds like this is the case for your boat. When you mentioned carpet fibers, I thought you meant that they were removed at the pump.

sdesmond
05-27-2008, 03:10 PM
I was referring to a screen at the pump inlet. Fibers get past the fuel pickup and collect at the pump inlet screen, and it sounds like this is the case for your boat. When you mentioned carpet fibers, I thought you meant that they were removed at the pump.

Wow... I feel like a dumba$$.. I honestly confused myself. I checked at the pickup in the tank. Not the fuel pump though. I didnt put 2 and 2 together and was thinking that was the pump when in reality it is not. When he had the boat serviced they were removed at the pump. I was just looking at the wrong place.

robled
05-27-2008, 11:22 PM
I am having the same problem with bogging. It started last year at the end of the year, labor day weekend. It started at the top of the throttle only. Then it moved to many places in the throttle range. At the start of this year we did cap, rotor, module, etc. for the fire side. We changed the fuel filter, etc. We took to the lake and tested for 30-45 minutes and the boat ran fine. Tought we had it fixed. We then went for the memorial day weekend and the problem came back. When the weekend was over i could hardly make it to the ramp. We chaked the fule pressure and it was 16 PSI. We took the tank out and everything looked good. Let me know what you find. I will keep you posted.

robled
05-27-2008, 11:24 PM
BTW my boat is a 1996 pro star 205 with EFI.

sdesmond
05-27-2008, 11:47 PM
I am having the same problem with bogging. It started last year at the end of the year, labor day weekend. It started at the top of the throttle only. Then it moved to many places in the throttle range. At the start of this year we did cap, rotor, module, etc. for the fire side. We changed the fuel filter, etc. We took to the lake and tested for 30-45 minutes and the boat ran fine. Tought we had it fixed. We then went for the memorial day weekend and the problem came back. When the weekend was over i could hardly make it to the ramp. We chaked the fule pressure and it was 16 PSI. We took the tank out and everything looked good. Let me know what you find. I will keep you posted.

I am hoping to have an answer friday night. I will let you know what I find. Mine dosent give me any indications when I am cruising till I get on it a bit. When it comes off the lift it has full power. Just after its been running for a bit it happens. If I dont get on it during the ride I probably wouldnt even know there was a problem.

JimN
05-28-2008, 09:38 AM
robled- if you have the LT-1, 16 lb is not enough- you should see 30 lb of pressure.

rspiecha
05-28-2008, 05:00 PM
Does the exhaust smell rich at idle??? I had a 1994 Prostar205 TBI 350 with a bog issue and rough idle, that was fixed with a new throttle body (which includes an internal fuel regulator and two injectors) I had replaced practically everything else in the EFI system to no avail. (including EFI brain box, ended up with a MEFI II box). Also, the dealer removed the water/fuel seperator early on in the boats life, and added a filter back by the fuel tank. Also, the engine had a 160 degree thermostat vs the stock 143 degree unit.

Rob

sdesmond
05-31-2008, 12:09 PM
Thanks to everybody who helped out on here. As always JimN was right on the money. I removed the fuel pump and the screen was clogged with carpet fibers. I dont even know how any fuel was getting through there at all. What bothers me is when my cousin had the boat he had the tank cleaned. Is there a way fibers are getting back in there?

JimN
05-31-2008, 04:14 PM
You found it! WOO HOO!

I think the fibers originally got in there because of static electricity in he factory and individual ones would be really hard to see.

One of the reasons they were so adamant in putting the pump in the tank for best performance is that at low pressures, gasoline 'shears' very easily. For a great example of this, turn the faucet in your kitchen on at a trickle and watch the stream. At low flow rates, it's solid but when you increase the flow or pressure, you'll see that it aerates the stream. This is fluid shear and when it happens in a fuel line, at best, it drops the pressure a bit (air can be compressed) and at worst, the motor runs lean. Any obstacle in the fuel line at low pressure will alter the flow and at high pressure, it's harder for the bobbles to form, just like water boils at a higher temperature at sea level than it does at high altitude.

The gas flowed around the fibers because the spaces were large enough and the suction was sufficient. My guess is that the screen on the pump wasn't cleaned. If you go to ask the service shop if they cleaned that, don't ask about that screen, specifically. Instead, ask them to show you where they looked and what they cleaned. Then, explain that carpet fibers in that screen isn't a new thing. If they're a MC dealer, they need to read all of their service bulletins.

Pursleym
06-23-2008, 12:00 AM
I am having the same issue as robled (96 ProStar 205 bogging down) The boat has been running great since I've owned it. Today, I noticed hard starts. Then when coming in, the boat would starve for fuel under acceleration above 3K RPM. Out of gear, revs great. Under load, the motor would bog, pull the throttle back, it would pickup power. The boat had only a 1/3 of a tank and it was a choppy (waves) back, so I wonder if I picked up debris. I will change the filter (not been done since I've owned the boat) and clean the screen in the pump. I am wondering about corroded grounds, though, because I had a car do the same and it was a corroded ground lead to the pump. Any help from you guys would be appreciated.

Mike

JimN
06-23-2008, 08:34 AM
How long have you owned it? If the fuel filter has never been replaced, that's where you need to start, especially if it starves at about 3K. This, and most threads about clogged fuel filters, follow your symptoms exactly.

Remove the fuel pickup tube and make sure that's clean, too. If it's not, remove the plate that holds the pickup and sender, so you can look into the chamber to see if there's any debris.

I doubt you recently picked up the debris, it probably accumulated over the years.

sdesmond
06-23-2008, 09:07 AM
Mine is actually starting to do the same thing again. Only this time it is do it about 4000 rpm. It is doing the bogging like starving for fuel and then I pull back and it is good. I normally dont run it that hard but I want it to be right. I pulled the fuel pump again and all is well in there. I am going to change the fuel filter again. I just changed it 3 weeks ago but I guess it cant hurt anything. I am also going to pull the pickup in the tank and check it out but I doubt thats it. Hopefully I find it. It was running great since I cleaned the screen on the pump. Ive only put about 5 hours on it so it. I may pull the tank and have it clean it while im at it.

JimN
06-23-2008, 10:04 AM
After finding all kinds of stuff in the fuel pickups, I had just gotten into the habit of checking and cleaning it. Remember, that's hte first placer any of the stuff in the tank oes before heading to the filters.

Pursleym
07-06-2008, 07:26 PM
Problem fixed. My 96 PS205 that was bogging was caused by the screen on the fuel pump. Took the pump off, cleaned the screen, and boat runs great again. Thanks for everyone's help.

sdesmond
07-06-2008, 11:49 PM
My boat has actually become undriveable.It died on my today. Wont go over 1000 rpm while under load. Next weekend I am checking fuel pressure. I pulled the tank and nothing is clogged there. Pulled the pump again and all is well. Also replaced the filter. I am wondering if the pump is shot or if the injectors on the TBI are clogged. This is the same thing that happened to me before. The problem gradually has gotten worse over time.