1999 7.4 Volvo Penta running rough

[alindquist]

I took my boat out yesterday (1999 232 Cobalt) to give it a test ride and I'm having the same problem that I had a few weeks ago. Basically here it is; boat seems to idle fine but once under power engine is running rough (vibrations) then once you get to about 2500 - 3000 RMP's I'm hearing a popping/wrapping sound. It sounds pretty bad. I'm at a loss. I have recently (within the last month) replaced the plugs, wires, cap, rotor, impeller, fuel filter, oil change, risers, manifolds, and the associated gaskets. I'm really hoping that this is an electrical problem but I have no idea. Could that happen if I had a bad wire or the wires were in the wrong place? So far I have dropped about 2 grand into this boat and needless to say I'm a little frustrated, any ideas where to start.
Aaron

 

[alindquist]

Re: 1999 7.4 Volvo Penta running rough

I should also mention that I just had check on the computer and there are no fault codes

 

[Don S]

Re: 1999 7.4 Volvo Penta running rough

Have you done a compression test on the engine? What were the numbers?
If you suspect plug wires being crossed, re-check them.
What is the Full model number of your engine? Volvo lists nothing by year. Even better, what is the engine SN.

 

[alindquist]

Re: 1999 7.4 Volvo Penta running rough

Compresion test was done and everything was good (I don't know the exact numbers however the mechanic that did it said everything was fine). Motor is a 1999 7.4 GI.

 

[Don S]

Re: 1999 7.4 Volvo Penta running rough

Post the numbers when you get them. You may have a 99 boat, but that doesn't mean the engine and drive are. I've been burned to many times on EFI information by trying to use boat year.

 

[alindquist]

Re: 1999 7.4 Volvo Penta running rough

hopefully this makes sense to you, here are the numbers I got off the motor:
7.4GI
411017645
386894

 

[Don S]

Re: 1999 7.4 Volvo Penta running rough

Almost, 411017645 is the number I need, however, it's one number short. The 386 number is also one digit short.

 

[alindquist]

Re: 1999 7.4 Volvo Penta running rough

try 4110176452, the dam sticker is ripped right at the last number...

 

[Don S]

Re: 1999 7.4 Volvo Penta running rough

Great, the full model number is 7.4GI PWTR
I will get you some info here shortly.

 

[alindquist]

Re: 1999 7.4 Volvo Penta running rough

thanks don, I may have found the problem, looks like 2 wires were backwards, I swaped them, and I'm going to bring it to the water, I'll let you know...

 

[Don S]

Re: 1999 7.4 Volvo Penta running rough

What 2 wires????????

Disregard
Plug wires................ Doh

 

[alindquist]

Re: 1999 7.4 Volvo Penta running rough

2 spark plug wires were backwards, swaped them, boat runs great now. Amazing that after having 3 techs look at it nobody picked up on that... I do have another question but I'll post a new topic, thanks again...