volvo penta 5.7 gs runs rough under load

[faber]

Recently purchased a 98 larson 236 lxi with a volvo penta 5.7 gs, sx outdrive. boat had starter trouble and starter was replaced. Starter still didnt mesh with flywheel so the ring gear on the flywheel was replaced. after this the boat started, and ran smooth for a whole day on the lake. next morning got in the boat which started right away and ran fine. we tried to pull some novice skiers and did a bunch of starting and stopping for about an hour. the boat then started to run really rough. when in neutral it will idle ok and rev smoothly up tp 4000 rpm (probably higher but i didnt want to rev it up that high) but the second it is in gear it feels like it is running on 4 cylinders. it will not go above 2000 rpms at wide open throttle, and when at wide open throttle it misses and runs rough. no water in the fuel was found at the filter, and we ran a bottle of fuel injector cleaner through the carb by pouring it into the filter directly. the mechanic was looking for the shift interrupt switch but could not find it. he said he is more familiar with mercruiser and not so much volvo penta though. any ideas here? do you think it could be ignition related? maybe condensation in the distributor? he did find water in the oil when he changed the oil also.

 

[captmello]

Re: volvo penta 5.7 gs runs rough under load

Welcome...

Doesn't sound good...Hard to say where to start.

When was the last full tune up?

Water in the oil is not a good thing.

Could the boat have been winterized incorrectly and froze last winter?

Does the boat have a closed cooling system or raw water cooled?

Volvos don't have shift interrupt switches, don't let that guy work on your boat.

We'll get to the bottom of it.

 

[faber]

Re: volvo penta 5.7 gs runs rough under load

I have a theory, but i wont be able to get it tested until tommorow. I think it is raw water cooled. Going to have them check for water in the oil tommorow. I think that some water got onto the distributor when a ski was stored in a ski storage slot located above the motor. The boat was running strong until the ski was stored. I bet the boot was full of water and that water ended up getting dumped on the distributor. I don't know about the boat being winterized properly or not. I am in Arizona and it does get cold during the winter but not terribly cold. nevertheless it can freeze and if the boat was not winterized it may have some problems. The guy I bought it from could quite possibly be the coolest guy I have ever met, and I am certain that he will make it right if there is a problem. A bunch of water on the distributor could definately cause the symptoms the boat is exhibiting no?

 

[faber]

Re: volvo penta 5.7 gs runs rough under load

what kind of cap and rotor do i need to buy for a 98 5.7 gs/sx ?
I saved about $130 by buying the ring gear for the flywheel at an auto parts store, but i know the distributor needs to be a marine distributor.

 

[captmello]

Re: volvo penta 5.7 gs runs rough under load

You can get the cap and rotor at napa.

Still doesn't explain the water in the oil thing. If it was a closed cooling system you'd have anti freeze in the engine and a reservoir to hold the coolant.

 

[faber]

Re: volvo penta 5.7 gs runs rough under load

You can get the cap and rotor at napa.

Still doesn't explain the water in the oil thing. If it was a closed cooling system you'd have anti freeze in the engine and a reservoir to hold the coolant.

What year chevy 350 cap am i asking them for at napa? it is not a closed cooling system. The mechanic that has been doing the maintenance seems to think the water was from someone stopping the boat too fast and water backing up the exhaust. not sure i buy that though.

 

[captmello]

Re: volvo penta 5.7 gs runs rough under load

What year chevy 350 cap am i asking them for at napa? it is not a closed cooling system. The mechanic that has been doing the maintenance seems to think the water was from someone stopping the boat too fast and water backing up the exhaust. not sure i buy that though.

Tell the guys at napa you've got a 1998 Volvo Penta 5.7 gs. You can look the part# up yourself on Napaonline.

http://www.napaonline.com/NOLPPSE/(S(qh5ztn55wqtlcjz1xy0gqt55))/Welcome.aspx

The water backing up into the engine isn't very plausible. The water would have to first, get into the cylinders and then slowly seep down past the rings to get into the oil. This would also corrode the cylinder walls on the way down.

I'm not very familiar with your setup. You could get water in the oil through a head gasket, an oil cooler or through the Intake manifold as well. I think I would get it running correctly, and test it out. See if you continue to find water in the oil or not.

 

[faber]

Re: volvo penta 5.7 gs runs rough under load

Went up on friday night and tore into the ignition system. pulled the distributor cap, and it looked fine. put it back on and fired up the boat. Had to give some throttle to get it to stay running (roughly I might add) and noticed the exhaust manifold coupler was leaking water. I tightened that up and replaced the wet plug wires on the side of the motor. fired the motor up again, and it still ran rough. next morning I pulled all the plugs which were all black with carbon, and gapped totally wrong. compression tested the motor and all cyliners came back in th 160-165 psi range. replaced plugs, distributor cap, and rotor. Motor fired right up and ran smooth as a baby's butt. Ran it all weekend and it ran strong and without issue. no water in the oil so far.

SO happy!

Thanks all!

 

[proxyx]

Re: volvo penta 5.7 gs runs rough under load

The water backing up into the engine isn't very plausible. The water would have to first, get into the cylinders and then slowly seep down past the rings to get into the oil. This would also corrode the cylinder walls on the way down.

I've seen it... plausible to me. Water then travels through the intake, the rest of your description ok. Same with leaking exhaust.
You did well faber. Congrats. Been there...