Volvo 7.4 GI Runs fine on muffs/ not at all in water

[spardicus]

Just bought a 99 Regal with a Volvo 7.4 GI. Took it out for a test run for about 2 hours at time of purchase - No problems. Brought it home sat for a week then took it out with the family ran fine most of day. The last stop of the day in a cove had a little trouble firing up but eventually did. Returned to ramp and went and got the trailer and it would not start, just turn over. Bring it home put the muffs on it, starts right up, no problem. Change Oil, Filter, Water Sep, Plugs, impellar. put it on the Muffs fires right up, Go to the lake today, put her in the water and nothing just turns and turns, back on the trailer, Drove home about 20 minutes put on the muffs and again fires right up any idea's this is driving me nuts and I would really like to get this resolved before the 4th. She just will won't run in the water.

 

[spardicus]

Re: Volvo 7.4 GI Runs fine on muffs/ not at all in water

Anybody ???

 

[DeskJockey]

Re: Volvo 7.4 GI Runs fine on muffs/ not at all in water

I wish i could help. I've got a 2000 ChrisCraft with a 4.3Gi; i haven't experienced anything like that. Does the engine crank, but not fire? Do you have the throttle lever in neutral? As weird as it sounds, i had that problem at the dock one time. It was pretty embarassing...

 

[spardicus]

Re: Volvo 7.4 GI Runs fine on muffs/ not at all in water

She's in neutral everythings as it should be, turns over just wont fire when its in the water, craziest thing I have seen, just fishing for some different ideas to try.

 

[slydog75]

Re: Volvo 7.4 GI Runs fine on muffs/ not at all in water

I hate to tell you this but it really sounds like a coincidence so far. I could see if you were having heating problems on the water that you didn't on muffs, but not starting at all? I just can't see anything that would change between muffs and on water that would affect if you could start.

 

[kg5388]

Re: Volvo 7.4 GI Runs fine on muffs/ not at all in water

a friend had that problem turned out that it was some kind of bad flapper in the exhaust.

it had come loose and fell down in the pipe and with the boat in the water it created back pressure and would not start

 

[QC]

Re: Volvo 7.4 GI Runs fine on muffs/ not at all in water

Do a search, some recent threads dealing with same . . .

 

[spardicus]

Re: Volvo 7.4 GI Runs fine on muffs/ not at all in water

UPDATE -- Still confused as all get out -- Today I woke up put her on the muffs and again fired right up. Head out to the ramp. Started on the ramp backed into water and she ran like a champ, sat there and idled while I pulled trailer and then ran for an hour and a half, Purred like a kitten. this both from putting around and WOT. Come back to ramp and tie off, shut her down and no start, pull her out on the ramp spits and sputters and tries but doesnt start, tow home about 20 min pull in drive fire's right up. This is insanity. It's got to be something small it just runs to good when it is running but it will not restart in the water.

 

[QC]

Re: Volvo 7.4 GI Runs fine on muffs/ not at all in water

Head out to the ramp. Started on the ramp backed into water and she ran like a champ, sat there and idled while I pulled trailer and then ran for an hour and a half

I think there is a clue there. Did you start her on the ramp before the water intakes were underwater?

Come back to ramp and tie off, shut her down and no start, pull her out on the ramp spits and sputters and tries but doesnt start

Were the water intakes out of the water when she sputtered? Partially?

Do a search for exhaust shutters . . . The one thing consistent in everything I have read here is that you have trouble when there is significant water pressure on the exhaust stream prior to start. Once running, she keeps running, and the exhaust flow would be theoretically fighting back at the water pressure, even at idle. Closing off exhaust is as significant as closing off intake. No air, no start.

Just found this . . .

 

[oops!]

Re: Volvo 7.4 GI Runs fine on muffs/ not at all in water

what was the engine temp when it started sputtering?

the muffs will have the water pressure of the hose.
but either way....it does not explain the no start

 

[spardicus]

Re: Volvo 7.4 GI Runs fine on muffs/ not at all in water

QC - I am going to tear down the exhaust in the morning and check out the flapper situation, I can see where that could potentially be a cause, I have been going around this for a few days, there is definitely something going on when the outdrive goes into the water, I have been told to check the grounds done that, been told to check alternator, charging system and batteries are full and charging. The anodes are busted up pretty good under the outdrive but I don't think that would have anything to do with it. If not the exhaust are there any other electrics that are killing the fire from the outdrive. Its either the exhaust deal or something is shutting down the spark when it goes into the water, I know I am getting fuel, fire I will have to check, but I definitely have fire when its out of the water. The temp at sputtering was 170ish generally stays right there all cooling seems to be good.