Mercruiser 3.0 running problems

[ronboy109]

Hi, thanks for the addition to the Forum.

I am currently having an issue with my 1992 Bayliner Capri.

Boat starts fine when cold, and revs freely when not in gear, (and in gear on muffs), once the engine has heated up (not overheated) it is difficult to start, requires full throttle and cranking.

IN the Loch it is a different matter starts easily, revs freely, whn in gear it will run roughly at low speeds, but wont go above 6 MPH, loses power and sometimes stalls if not caught, when warm it wont start, except occasionally with cranking and full throttle.. most just doesn't start.

I am thinking pre carb problem (i.e. pump, filters or anti siphon) as the carb seems dry .

I am happy for suggestions if this is the correct area to be looking in, sparks seem fine, and all electrics seem okay too.

Cheers

R

 

[alldodge]

I am thinking pre carb problem (i.e. pump, filters or anti siphon) as the carb seems dry .

Howdy

You have the right idea, start with those and see if you can get some fuel to the carb if it is dry.

Would also suggest a compression test

You could put a couple ounces of gas down the carb to see if it will fire right up. If it does fire right up then it is lack of fuel. If it still does not fire up then start looking to see if the carb is flooding the motor. Pull some plugs and see if they are wet

 

[ronboy109]

Cheers friend, will get right on to that.. Could a worn distributor cause similar problems if I am getting fuel?

 

[alldodge]

If you had points maybe, but you should have electronic so probably not

 

[RyanW1985]

Start with compression test, if it is running at all you are getting fuel. Heat would cause things to expand and open tolerances from blown head gasket, cracked head or block making it worse until cool. Will cause no performance because of load on engine.

I had same problem when I bought my 3.0 and it was head gasket

do you have better history on boat overheat, hard shutdown, do you have flapper still....

 

[RyanW1985]

Duplicate

 

[ronboy109]

So just went up to the boat, don't have my compression tester as a friend has "borrowed" it (about 2 years ago!) Tried to start it, took a lot of cranking from cold and full throttle Also had a look inside the distributor, to find the inside electrodes heavily furred, and one of the external electrodes badly corroded.

Oil is not milky, and no smoke in the oil.

Will compression test tomorrow.

 

[ronboy109]

I cleaned out the sight tube and there was oily petrol gunk in there , is this normal?

 

[alldodge]

I cleaned out the sight tube and there was oily petrol gunk in there , is this normal?

If your talking about the "sort of clear" tubing which goes from the pump to the carb, then there should be no fuel in it. If there is then the fuel pump diaphragm has ruptured

 

[ronboy109]

yes, the yellowish tube, not a lot of fuel but definitely some.

 

[alldodge]

yes, the yellowish tube, not a lot of fuel but definitely some.

Your fuel pump is gone. Part number 8M0073435 item 1

http://www.mercruiserparts.com/bam/subassembly/30914/1604/110

 

[ronboy109]

Phew, compression is about 120-130 in each cylinder... however after reinspection of the plugs they are heavily sooted....

I did my spark tests without extracting the plugs

 

[alldodge]

Maybe new plugs and fuel pump and you will be boating again

 

[ronboy109]

Carb rebuild finally fixed this...