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Volvo penta 250a engine starts missing at high revs.

B

biffa

New member
Hi

I have a sealine 270 with 2 volvo penta 250a engines, recently the port engine has stated to miss and loss power intermittently when run for 20 minutes or more at 4000 to 4200 revs, if I bring the boat off the plane and let the engine idle it runs fine and revs ok, so put the power down on both engines the boat gets back on the plane and about a minute later the port engine starts missing again. the engine will run at lower rev 2000 - 3000 with no problems, the engines are in good condition with 80 lbs of oil pressure, water temp normal, complete new ignition systems on both engines, when the port engine stats to play up the engine noise deepens and there's a strong smell of petrol, I've been over and over the ignition systems and its all in perfect tune. I,m sure i have a sticking exhaust valve.


I hope some one can help.

Thanks
Paul
 
If you are sure that you have a sticking exhaust valve, then I don't understand the nature of your post.

From my perspective, it could be a number of other things, including: faulty distributor, faulty ignition wires, faulty spark plug, faulty coil, a faulty ignition switch, a bad wire connection, a carb overflowing, a fuel pump with a ruptured diaphragm ....

Do you have points or have you converted to electronic? That is, have you installed a Hot Spark or a Pertronix electronic ignition kit?
 
Hi... I have had a similar problem to what you are describing (I think). Unfortunately I haven't been able to find the fix yet, but can maybe rule out a cpl things if it is indeed the same issue.

I have a Four Winns Vista with a single 5.8 Volva Penta. After running on plane the engine begins cutting out as if it is choking for fuel. It does not do it in nuetral or at low revs in gear. It has progressed to the point that I am unable to sometimes put the boat up on plane at all. It starts cutting out at around 10mph... It started doing this last fall. Our mechanic thought that he fixed it when he winterized it and we had 5or 6 clean runs out of it this spring but last week it started doing it again.

So far all the fuel lines/filters---distributor---battery cable/conections--- have been ruled out.

I have googled and found references to the rev-limiter caused by a slip in the prop hub but am curious if it could have anything to do with a throttle cable as the problem started shortly after I had it replaced.
 
The original poster mentions a strong smell to gasoline, this is what makes me think that fuel starvation does not appear to be the problem.

I mentioned a ruptured diaphragm as a possibility because mechanical fuel pumps are moved by the engine, so the higher the RPM the higher the volume of fuel being pumped to the carb. If the diaphragm is perforated, the fuel leaking through the rupture gets sent to the carb via a plastic line, and that would cause an overly rich mixture. Other than that or a flooding carb, I can only think of an electric choke not working properly or an ignition problem. I cannot see a sticky exhaust valve causing a strong smell of gasoline.

The rev limiter is electronic and would cut the ignition if I remember correctly.
 
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