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43 revs up and down by itself

murray59

New member
"My son-in-law picked up a nic

"My son-in-law picked up a nice 94 Maxim 2000 sr2 with a 4.3 mercruiser with alpha one drive. It's happened a couple of times that while cruising along part throttle the motor started revving down and up a bit while slowly losing rpms and speed. When I was with him he pulled it back into neutral and revved it up a few times just fine. When it does this the motor sounds just fine, no missing or sputtering or coughing. I thought he was horsing around until I looked over and his hand was not on the throttle. When he first got it it was checked over and fuel was changed out and a fuel filter was replaced. I'm guessing some kind of fuel problem. Any ideas??"
 
Are you sure it is not just th

Are you sure it is not just the throttle quadrant backing off on its own?
I know a couple of boats that do this. Quite annoying.

Rod
 
Check inlet screen at carb and

Check inlet screen at carb and anti drain back at tank. Also check vent line from tank to Filler
neck for blockage. Being a 94' I would consider
a full tune up if no true history is known. Also
could be debri floating around in carb float bowl.
Kurt
 
Problem solved! He removed the

Problem solved! He removed the check valve in the fuel line that was located right at the tank and it's been good so far.
 
a shame his insurance wont cov

a shame his insurance wont cover him in case of fire.CG Regs require a positive fuel shut-off to prevent fuel from syphoning out of the tank.
either a manual valve or a anti-syphon valve.
 
"Murray

You need to fit a n


"Murray

You need to fit a new anti syphon valve as the BT Doc has suggested for your own safety and peace of mind or you can fit an electric 12v fuel lock and use your ignition to activate the lock. No power to the lock, No fuel flow.

Cheers
Peter C"
 
"I don't think this check

"I don't think this check valve is an antisiphon, I think it's an anti drain back as Kurt S. described it. It had a ball and spring that allowed fuel to flow toward the engine but not back to the tank."
 
"Murray

Let me put it to yo


"Murray

Let me put it to you this way, if you can remove your fuel line up near the engine, place it low enough in the boat that gravity takes over and fuel begins to run unchecked into the bilge you have a potential BOMB
sad.gif
.

Plenty of people every year get a crash course in walking on water when their boat explodes from fuel in the bilge from a ruptured or damaged fuel line.

We had a case here about 6-8 weeks ago where a cruiser blew up killing both people on board from fuel in the bilge and a mate lost his 34ft er in a fire from suspected fuel leak into the bilge about 4 weeks ago.

Safety of all on board is the masters number one priority, as far as I am concerned the electronic fuel locks are one of the best investments in safety on boat that can be fitted.

Am I making myself clear ? for starters your son in law now knows there is a potential safety issue there and should there be a majour catastophy involving members of your family for example and an investigation is held what do you think the insurers will say about any claim.

Just replace the valve or fit a lock and everyone will be able to sleep well tonight.

Sorry if I rambled.

Cheers
Peter C"
 
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