Fuel question...

H

huckle

Cadet
Joined
Jun 5, 2009
Messages
20
Hey just curious if anyone can give me ideas on what I can do to improve my 3.0 Mercruiser engine fuel situation. It is a 4 stroke. It starts fine at cold start. I have to choke the engine. After running it for awhile in the lake we often stop to let the kids go for a swim in the lake. After swimming in the lake we go to leave and it seems that the engine is hard to start. I still have to choke the engine to get it to start. I find this odd being that the engine is still warm. Is this normal? Could someone give me ideas to as to what to look at? The water seperator was cleaned last winter. Spark plugs look fine.

Thanks
 
C

Chaparral220

Cadet
Joined
Jun 11, 2009
Messages
26
Re: Fuel question...

Are you running last year's fuel? Could be a touch of vapor lock. Let the engine idle for a minute when you stop and see if that allows it to cool a bit before shut off. I had a boat that ran better on higher octane fuel in terms of shut off and start. However, will want want to go cheaper fuel if can!

I am currently having a similiar issue for the first time ever. Wonder if fuel blending is different this season!
 
Bondo

Bondo

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Staff member
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Apr 17, 2002
Messages
70,513
Re: Fuel question...

and it seems that the engine is hard to start. I still have to choke the engine to get it to start.
Click to expand...

Ayuh,... My guesses are,...
The motor needs a Tune Up,+ the Carb needs Rebuilding...
 
S

Schmoe

Petty Officer 2nd Class
Joined
Feb 10, 2004
Messages
117
Re: Fuel question...

Explain "choke the engine." Are you having someone manually close the butterfly valve on top of the carb while you crank it? Or it just won't hit when you turn it over so you pump the throttle in the neutral position and then try and fire it up? If so, could be one of two things, idle adjustment is off, carb choke setting is too rich. You can adjust both. If your running the engine hard and then shut it down, the 3.0 is notorious for dieseling. You got to give those little engines time to burn off all the fuel that was shoved down it's throat. I had the same problem until I changed tactics.
 
H

huckle

Cadet
Joined
Jun 5, 2009
Messages
20
Re: Fuel question...

Thanks for the advice. When I bought the boat I was told to run 87 octane, and that is what the manual calls for. The guy I bought it from says the carb what cleaned and rebuilt about 5 years ago. I just dumped a can of carb cleaner into the gas trying to see if that helps. I am also running new gas. When I choke the engine I am doing it from the throttle in the captain seat. I will try to let it idle for awhile before I shut it off to see if that helps.

Would running higher octane be better? I was told 87 octane gives better HP.
 
Don S

Don S

Honorary Moderator Emeritus
Joined
Aug 31, 2004
Messages
62,321
Re: Fuel question...

When I choke the engine I am doing it from the throttle in the captain seat.
Click to expand...

You don't "Choke" the engine with the throttle lever, all you are moving is the throttle linkage on the carb. The choke is automatic.
EXACTLY what procedures are you using when starting the engine cold, and then how do you start it with a warm engine.
 
bustermin

bustermin

Banned
Joined
Apr 13, 2009
Messages
315
Re: Fuel question...

It's time for a carb rebuild... 5 years is a pretty good run, remember its not a car that runs for a while each and every day, when fuel sits in a carb it turns to varnish over time, and carbs and bad fuel dont like each other, and tend not to get along. a carb rebuild is fairly inexpensive especially if you do it yourself. do a carb rebuild and while your at it just do a basic tune-up, it's obviously time for some maintanence.
 
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