Mercrusier 165 Problems

Joined
Jun 19, 2012
Messages
11
Well today i tore the heads and exhaust off the motor...its a 1970's straight 6 165hp...im not sure of cylinder numbers and what not but if we start from the bow it goes from good to worse..bow back 123456 just for this post refrence..got water in oil and i panic and tore down. i tested block heard some hissing from in the oil cap. I then double checked the manifolds and riser they are not leaking (prob wont be long) the cylinders that have water in them are 5,6. 6 is the worst with some slight rust the sparkplugs for 5 and 6 also look clean also water is laying in the 6 cylinder post removal of head. i dont think the block is cracked cause i have the boat jacked up leaning a bit back so bilge could drain and there is still water in the block by the #6 im thinking head gasket....which was damp slightly...if there was a internal crack in the block there would be no water in the system right it would of by now been in the oil? also the #6 is at the top of its stroke so if it was leaking would be in the oil pan not in the water jackets right? i dont have pics right now but may by the end of the week cause the head in going out for work. plus i drive truck and only had a few hours home? someone have more insight?
 

kd7isf

Petty Officer 2nd Class
Joined
Aug 20, 2004
Messages
162
Re: Mercrusier 165 Problems

First, you are correct about cylinder numbers 1 is closest to bow, 6 closest to stern.

I'd say you're riser and by now probably your manifold is shot. This is typical of a rotting out riser, and since it's on the back, the cylinders back there get it worse....

IF there was a crack, you would see it.

Get the water out of the engine ASAP!

Then crank the engine around and look at the cylinder walls.. If they are cracked, you'll see it...

Hope this helps
 
Joined
Jun 19, 2012
Messages
11
Re: Mercrusier 165 Problems

Well I did get most of the water out at least as much as I could the water filled cylinders I dried up put some oil in it to help stop the rust so I can preserve it till I get home this weekend the riser didn't look cracked but I'll get some pics here I hope by Sunday the riser dumps the water back out at the end right? I'm not a complete cityidiot...I've rebuilt plenty just this leaky manifold stuff got me going bonkers
 
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