1982 mariner 15hp starts for a few seconds then dies

[tomisty05]

I have a 82 mariner 15 hp, I had the carb rebuilt, all fuel lines replaced, fuel pump rebuilt, I have a good spark on both plugs, and Im getting fuel. When I pull start it, it fires right up but will only run for a few seconds, sometimes maybe 10 seconds. If I try to give it throttle it makes it worse and dies instantly. Almost makes me think maybe the exhaust is clogged? Is this possible? I made sure the set screw is 1 1/2 turns out, and bought a new fuel can and mixed new gas at 50/1. This motor sat for about a year. I am a little concerned with the fuel pump also, I am not sure if this works or not but I bypassed the fuel pump, put my fuel tank up on a ladder and ran it straight to the carb to try gravity feeding and it does the exact same thing. But Im not sure if this can be done. Any help would be great. Thanks!

 

[CharlieB]

Re: 1982 mariner 15hp starts for a few seconds then dies

Try leaving the choke half on to see if it will continue to run.

Also try covering/sealing off one carb with the palm of your hand just as it begins to falter to see if it will continue to run on one cylinder.

Also try spraying more premixed fuel into the carbs as it begins to falter to see if that helps.

I'm thinking that the crankseal between the cylinders may have failed. Typically when that seal fails we loose idle, it dies, but adding fuel it may run at a fast idle.

Once started immediately open the throttle, a faulty crankseal will run more or less OK at WOT, but die anywhere near an idle.

 

[tomisty05]

Re: 1982 mariner 15hp starts for a few seconds then dies

Also try covering/sealing off one carb with the palm of your hand just as it begins to falter to see if it will continue to run on one cylinder. I ONLY HAVE ONE CARB, BUT PUTTING OUR HAND OVER IT SOME LETS IT RUN LONGER. THIS WORKS!
BUT WHAT DOES IT MEAN?

Once started immediately open the throttle, a faulty crankseal will run more or less OK at WOT, but die anywhere near an idle. THIS IS HAPPENING ALSO!

Try leaving the choke half on to see if it will continue to run. THIS DOES LET IT RUN BUT EVENTUALLY DIES IN ABOUT 15 SECONDS!

Also try spraying more premixed fuel into the carbs as it begins to falter to see if that helps. I HAVENT TRIED THIS BUT WILL TOMORROW!

A friend helping me said it looked like water was getting into the gas, is this possible?

I appreciate the help, you are hitting the nail on the head with what to do. Thanks!

 

[tomisty05]

Re: 1982 mariner 15hp starts for a few seconds then dies

I just want to clarify the water in the gas, I have a brand new fuel tank with all new fuel lines, bowl emptied and cleaned and all new fresh fuel in the tank. When you pull one the spark plugs, the have little beads on them that he said looked like water.

 

[mark_gober]

Re: 1982 mariner 15hp starts for a few seconds then dies

Tomisty,

The set screw that you referred to...which one is it? Is it the one just above the intake on your carb? I have a 1985 18hp and mine is just above the intake. Mine has to be set pretty precisely or it won't run. Mine sits just below flush with the face of the carb. Maybe flush minus 1/2 or 1 turn. I adjusted mine by quarter turns until it would run and stay running. Also does your prime bulb get stiff when you prime it? Do you have gas spilling out anywhere on the carb?

Mark

 

[CharlieB]

Re: 1982 mariner 15hp starts for a few seconds then dies

AHA!

Forget the crankseal.

Little beads of water on the spark plugs indicate that the exhaust gasket/divider plate/water jacket is leaking water into the exhaust next to the exhaust ports, sucking it back into the cylinders, wetting and shorting the spark plugs out.

Remove the exhaust cover and plate, inspect the plate for any holes, pitted corrosion worn through it. Inspect the gaskets on both sides of the divider plate for any break that allowed the water to leak onto the exhaust side.

Clean all surfaces carefully with a gasket scraper, being particularly careful to NOT gouge any gasket surface.

Gently slide a file lengthwise along all gasket surfaces to ensure flatness.

Reassemble with new gaskets.

If the new gaskets do not have a small line of sealant down the center of each surface then LIGHTLY coat both sides with a good silicone sealer. And by LIGHTLY, I mean as thin as you possibly can, almost as if you are trying to wipe it OFF with a clean finger immediately after putting it on.

Hang the gasket on a nail or something to dry for 30 minutes to an hour BEFORE assembly to ensure the surface has lost all 'slickness' from the silicone.

 

[tomisty05]

Re: 1982 mariner 15hp starts for a few seconds then dies

AHA!

Forget the crankseal.

Little beads of water on the spark plugs indicate that the exhaust gasket/divider plate/water jacket is leaking water into the exhaust next to the exhaust ports, sucking it back into the cylinders, wetting and shorting the spark plugs out.

Remove the exhaust cover and plate, inspect the plate for any holes, pitted corrosion worn through it. Inspect the gaskets on both sides of the divider plate for any break that allowed the water to leak onto the exhaust side.

Clean all surfaces carefully with a gasket scraper, being particularly careful to NOT gouge any gasket surface.

Gently slide a file lengthwise along all gasket surfaces to ensure flatness.

Reassemble with new gaskets.

If the new gaskets do not have a small line of sealant down the center of each surface then LIGHTLY coat both sides with a good silicone sealer. And by LIGHTLY, I mean as thin as you possibly can, almost as if you are trying to wipe it OFF with a clean finger immediately after putting it on.

Hang the gasket on a nail or something to dry for 30 minutes to an hour BEFORE assembly to ensure the surface has lost all 'slickness' from the silicone.

WILL DO, TODAY IS MOTHERS DAY SO I MAY HAVE TO WAIT UNTIL TOMORROW OR I WILL HAVE BIGGER PROBLEMS THAN THE MOTOR. MY WIFE!!!! HAHA THANKS!

 

[tomisty05]

Re: 1982 mariner 15hp starts for a few seconds then dies

Ok will check the exhaust gasket/divider plate/water jacket, but I will probably have to wait until tomorrow, today is Mothers day and I will have bigger problems than the motor if I work on it today. My wife!!! haha I will get back with you. Thanks!

 

[tomisty05]

Re: 1982 mariner 15hp starts for a few seconds then dies

Tomisty,

The set screw that you referred to...which one is it? Is it the one just above the intake on your carb? I have a 1985 18hp and mine is just above the intake. Mine has to be set pretty precisely or it won't run. Mine sits just below flush with the face of the carb. Maybe flush minus 1/2 or 1 turn. I adjusted mine by quarter turns until it would run and stay running. Also does your prime bulb get stiff when you prime it? Do you have gas spilling out anywhere on the carb?

Mark

Yes Mark mine is in the same spot, but I have tried everything with adjusting the screw out 1 1/2 turns, then 1, then 1/2. The bulb pumps up fine, without gas spilling out.

 

[tomisty05]

Re: 1982 mariner 15hp starts for a few seconds then dies

Ok I changed the exhaust divider gasket, and I still have water on my plugs. Is the head gasket the only other part that water can get in?

 

[CharlieB]

Re: 1982 mariner 15hp starts for a few seconds then dies

Need your model and serial #'s to look it up to be sure, but........

Most small Merc/Mariners do not have a cylinder head, the cyl's are bored from the bottom, the cyl's are blind holes, not thru holes as with a conventional cyl head.

Water MAY enter a cyl IF there is a crack in the cyl (possible, but rare), the common fault is the exhaust divider plate and gasket failing to seal cooling water from the exhaust ports.

Are you CERTAIN that the divider plate is FLAT, no dents dings, gouges in the gasket area?

And that you have the correct gasket on the correct side of the plate?