91 merc 15hp . water in plugs/cylinders..help

[guggy]

Hi Everyone i really need some help .. I just purchased this 91 15ho merc and it ran great for a 20-30 sec's and than rought idle. I pulled both plugs and they both had water on them .. blew out the plugs and cylinders and it ran perfect again for 20-30 sec's unitll water build up in cylinders again. Compression test seems even and healthy but what can this be? I hear head or exaust gaskets may be gone but where should I start from ? Could this be a cracked cylinder head or block ? Any suggustions ?<br /><br />Thanks for any help or ideas.

 

[guggy]

Re: 91 merc 15hp . water in plugs/cylinders..help

Anyone ?

 

[guggy]

Re: 91 merc 15hp . water in plugs/cylinders..help

ttt

 

[Bob H.]

Re: 91 merc 15hp . water in plugs/cylinders..help

Do leakdown test versus compression test. If you have access to a plug in the water jacket you'll probably hear the leakage. I'm not familiar with that engine so I know if your engine has a real head or blind bore.

 

[guggy]

Re: 91 merc 15hp . water in plugs/cylinders..help

Hi Baitis,<br /><br />Thanks for your reply.<br /><br />I believe i have a blind bore . how can I tell ?<br /><br />Also how can I do a leakdown test ?<br /><br /><br />Thanks.

 

[jheron]

Re: 91 merc 15hp . water in plugs/cylinders..help

What ever you do don't run it untill you find out where the water is coming from. <br />I would say its time to get a manual ... <br />Jon

 

[guggy]

Re: 91 merc 15hp . water in plugs/cylinders..help

i agree jon .. The repair manuel is on order.<br />A<br />ny clues what I should look for ? Do you also know the torque to the blind bore bolts?

 

[guggy]

Re: 91 merc 15hp . water in plugs/cylinders..help

Have any of your experienced this on a similar hp motor ? What can cause this from happening ?

 

[guggy]

Re: 91 merc 15hp . water in plugs/cylinders..help

anyone ?

 

[inlineal]

Re: 91 merc 15hp . water in plugs/cylinders..help

Guppy...Are you sure it isn't gasoline flooding the cylinders.??...Like almost all Mercs they have no cylinder head and the chances of a cracked cylinder doom is almost nil..sometimes a leaky exhaust side cover but in this family of motors that also is unlikely...All Mercury 8hp thru 15 have had carb problems because of the crap fuel of today...The latest carb kits have been updated again...this time with better neopreme parts...These motors run good even on a bad day..I would let the cylinders flood out...remove the spark plugs and shake each plug into the palm of your hand and take a good whiff....or even a taste...I'm not saying it is not water..i just never run into that problem....good luck...Al...

 

[guggy]

Re: 91 merc 15hp . water in plugs/cylinders..help

Thanks for your reply inlineAL. <br /><br />Yes i'm sure it's water. I really hope the block isn't cracked or something major. I just purchased this motor and it wasn't "peeing" so it had no idea that it was taking water in the cylinders. I will change the gaskets for the side block cover and go from there. Does anyone know what I should torque these bolts need ? Should I use some or alot of sealant on the gaskets ?<br /><br />Any replies are GREATLY appreciated.<br /><br />Thanks again.

 

[inlineal]

Re: 91 merc 15hp . water in plugs/cylinders..help

Do not use any kindof ATV..Period...The silicone base of the stuff doesn't allow the gasket to do its job...In perfer Permatex Aviation sealer..and only a thin layer...The sidecover should be tightened evenly and tight...I don't know the torque..just don't try and twist them off...The bolts don't have to be that tight...For good measure I would change the exhaust plate with the new gaskets...and oh yeah....these motors have a thermostat that is at the end of the trail to the pee indicator...The water will not come out of the hole until the stat opens and the stream comes and goes as the stat opens and closes...

 

[guggy]

Re: 91 merc 15hp . water in plugs/cylinders..help

your the man inlineal !!!! I have done exactly what you said and BINGO , problem solved !!! Thanks a million to you al and all that have replied.