Boat Plane Issue - Bad Gas ???

[bout time]

This past season i could rarely get my boat to plane down. It is a 23' Renken Cuddy with 4.3 Mercruiser. The most i can get out of it is 3800 RPM WOT where before i was easily pushing 4400 rpm. I have checked the compression in all cylinders and they are fine. I have changed spark plugs with no improvement. i have not changed my prop. Could this be related to the "new" ethanol gas? what is the fix? for the most part i can live with it but when I am in 3-5' seas i need the power to counter the waves. any ideas?

BOUT TIME

[Misty IV]

I have heard about the new gas causing problems more recently, but not as much during the season. Ever since the new fuels have been introduced, I purposely carry a few spare water separating filters onboard. Knock on wood, I haven't had to change any while on the water, but nice to know I have them if the need arises. Only other thing I can think of is something mechanically fuel related, such as the fuel pump. Perhaps it isn't putting out as much as it should. Do you have a separate fuel filter inline with the fuel line? Maybe check that and see if it is clogged and not letting enough fuel pass through when the engine is requiring more. I'm no mechanical genius but those would be the little things I'd look at. Sure the mechanical individuals will offer some more input soon. Good luck and let us know what you figure out the problem is. May end up being something we will all have to worry about next season.

[dewey123]

it isnt the ethanol in the gas. All motors are made to run on 10% max ethanol blends unless it is flex fuel. My shop manual for my 89 outboard is made to run on 10 % ethanol. It is good to use the water seperating filters because ethanol holds water....doesnt mean you will pump water in with your fuel at the pump. Try putting some fuel system cleaner with some 93 octane and burn it up sounds like somethings plugged up.

[Gill-T]

Fuel issues, fuel filter issues, carb issues, fuel pump issues. Could be any of the above. Start with the easy fixes first......ie change fuel filter (dump out gas in glass jar and check for water), gas treatment such as stabil or seafoam. If you still have problems.....start thinking carb or fuel pump and a good marine mechanic.

[Splitshot115]

Check the choke, mine did the same thing, found that the choke thermostat got loose and moved. Put it back to where it should be and gained a little performance.

Scott

[Capt Vince Pierleoni]

A slight timing change can also give those symptoms.

[Yankee Troller]

We had a bad oil pressure regulator, I think, that was giving us that issue too. Krenzer had us up and running in a week.

[bout time]

Thanks for all the input guys. now i just need to wait for spring to tear into her!!!

[FLXTroutman]

I had a similar issue, low power, wouldn't plane out, and stalling at idle or trolling speed with my '85 Sea Ray with 350 Mercruiser. Finally took her to a real mechanic, not the guys in the marina who said I needed a carb rebuild. Main problems diagnosed were the timing was 16 degrees off, should be 8 degrees BTDC, mine was at 8 degrees after top dead center and rotor was not seated or "keyed" in place. All ignition parts replaced, timed, tuned, the ignition wires were original from '85 too, the mechanic couldn't believe it even ran. While he was at it all fluids changed, new prop, main battery cables relugged, new fuel lines. First time out with her after the repairs, I dumped the throttle and she jumped up right on plane with 4 people on board, coolers, and gear and hit 40 mph SOG in about 7 seconds.

Driving boat around running like crap: $0

Paying for repairs on boat: $1000

Having a mechanic who knows what he's doing (since I don't): PRICELESS

[L&M]

Very well said & true in most cases.