1996 Merc 150 HP Offshore V-6 Carburated

MaggieRose

Seaman
Joined
Oct 4, 2007
Messages
65
I have tried to take great care of my boat and engine since I bought them on 2001. The trim and tilt on my outboard required seal replacement and rewiring of the electric motor (repairs I did). Two weeks ago, while heading offshore with a couple of fishing buddies, I noticed a change in the sound of my engine while running at 26 mph (4800 rpm). I immediately shut it down, pulled the engine cover and checked it out. Nothing visibly wrong, heads were not overly hot (I could hold my hands on them), good oil level in the on board tank and covers on tight, and water was coming out of the tell tale when it was running.

I attempted to turn it over...NO GO! I attempted to spin the engine by hand in nuetral and she was seized. After getting towed back in, I pulled the heads (first time for me on this engine). I found aluminum from the tops of the #3 and #4 pistons in the cylinders. After vacuuming out the heads, exhaust manifold and water passages, I was able to turn the engine by hand.

I am working on getting some pictures on here.

While breaking down the engine I found the line going from the fuel enrichment valve to the middle carburators was broken. I assumed this was the cause of my engine problem.

I called a local Merc shop about working on the heads and was told they would only take the job with the engine intact (and gave a starting estimate of 4 THOUSAND)! I explained what I found and their mechanic does not think the open line on the carburator caused the 3 and 4 cylinder problem. He believes it was pre-ignition and/ or detonation. If that is true, how are only two cylinders affected by pre-ignition and/ or detonation?
 

gss036

Commander
Joined
Jan 18, 2003
Messages
2,914
Re: 1996 Merc 150 HP Offshore V-6 Carburated

OUCH! Probably would be cheaper to buy a rebuilt powerhead.
Those little clear hoses have a way of messing up motors as they tend to get brittle and split or break causing a loss of oil to the oil pump, then a seizure results.
I know of a couple of engines that have seized because of them.
Check on the prices here on IBoats for the power heads.
Good Luck.
 
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