Water in the Motor......Ugh!!

happysunshine71

Recruit
Joined
May 4, 2009
Messages
5
Recently purchased a 24' pontoon with a 90 hsp Mercury. After replacing the flooring and all the seats, we took it out for a run on the lake. Noticed it was not running smoothly. Found water in the #6 cylinder. Does anyone know what would cause this? I've heard from several locals who all have differing views. Do have some automotive mechanical skills but am new to the whole boat thing? Any advice?
 

a173765

Recruit
Joined
Apr 29, 2009
Messages
5
Re: Water in the Motor......Ugh!!

whats your water pressure at anny way u might have a leak/ crack in the head gasket it may also be a series of other bad things im sure a mechanic may be a better diagnosis
 

happysunshine71

Recruit
Joined
May 4, 2009
Messages
5
Re: Water in the Motor......Ugh!!

Haven't checked the water pressure since the mechanic we bought it from put a new water pump on. This particular motor doesn't have a head gasket.......???
 

Nippissinger

Petty Officer 3rd Class
Joined
Mar 2, 2009
Messages
94
Re: Water in the Motor......Ugh!!

happysunshine71 said:
This particular motor doesn't have a head gasket.......???
Maybe that is why you have water in the cylinder...
Something needs to keep the water out of the cylinders don't you think?
I am no mechanic so I may be way off when it comes to outboards...

Just my uneducated guess..

Will
 

cell

Petty Officer 1st Class
Joined
Apr 16, 2009
Messages
208
Re: Water in the Motor......Ugh!!

What year is the engine?Look at the top post in this thread and find out.Not all outboards have a head gasket...not all of em have heads.Theres a couple of ways water can get in there.
 

emckelvy

Commander
Joined
Jan 16, 2004
Messages
2,506
Re: Water in the Motor......Ugh!!

Inline Six Merc's are not manufactured with a cylinder head. The cover over the back of the block is just that, a cover.

The most likely sources for the water intrusion are bad crankshaft seals in the lower bearing cap, and leaking exhaust manifold gaskets. The motor's getting old enough to where either case is possible. Gaskets dry up and become brittle; rubber crank seals deteriorate and de-laminate from their metal shell and leak.

Either problem will require you to pull the powerhead to fix.

A freshwater motor will come apart easily; a Salty Dog is gonna require lots of heat and PB Blaster. Take care not to break bolts. Drilling out stainless bolts broken off in aluminum block is not fun!!!

With the manifold cover off, carefully inspect for signs of leakage. There's also an inner water jacket around the exhaust port, which is prone to leak. Check the exhaust baffle plate for perforations and replace if it's bad.

The lower bearing cap can be removed without splitting the crankcase. Use a puller in the threaded holes in the cap. If you don't use a puller and pry on the cap instead (not recommended), just be extremely careful. The mounting 'ears' on the bearing cap can be broken if you reef too hard. Loosen the bottom (2) bolts which secure the 2 halves of the crankcase together, this may make cap removal a bit easier.

Note how the seals are oriented in the cap, then drive them out; the new ones are pressed into the cap same as the old. I use a thin coating of Permatex #3 aviation dressing on the O.D. of the seals and that's always worked for me. Use a new O-ring on the bearing cap and spread a thin layer of marine-grade grease on the O-ring. Draw the cap back down into the block evenly or you'll bust something! Note that the mounting tabs on the cap are offset and the cap will only fit one way.

The exhaust manifold bolts require 150 inch-lbs of torque, too little and the covers won't seal.

Anyway, that's a quick-n-dirty synopsis of what you'll need to do; plenty of the 'fine' details are omitted; recommend you purchase a manual so you'll have all the info you need to git 'er dun.

HTH & G'luck.........ed
 
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