Merc 165, oil in water + ID question

Heyy all.
i got a Mercruiser 165, 6cyl inline engine s/n 5027010 and the s/n on the drive unreadable except for the "165" as the engine is called so.. How do i ident my drive so i can buy a new propeller, and what is the drive called and what is the engine info.

When i bought the boat i knew it had water in the oil and hoped it was a head gasket, but the gasket looked fine. The head has no cracks or corosion.

I pressurericed the manifold by conecting a waterhose to the stud on the end and putted a blankingplate under the knee and found a minor crack in the exhaust part (about 1 drop of water every 2 second) but i dont belive this could get that much water in the engine because of the exhaust pressure and the heat in the manifold.(or should it be replaced?)

So my own theory is, that the water can only get in from a cracked block or from a worn knee gasket..

Have i overlooked anything i should try investigate?

pleace dont hesitate to ask me for info or reformulate of questions

Re: Merc 165, oil in water + ID question

If you have a prop look at the end for the part#.You didn't say what size boat or how it's gonna be used how many people etc. Any info will help figure out the prop size.If you are getting water in the oil it could come from a lot of places.Left uncovered is #1 a bad riser is #2 and a bad manifold is #3
That manifold is pretty pricey 500+ Make sure it aint bad first.Usually the riser is the culprit. Jerry

Re: Merc 165, oil in water + ID question

this is a good read....

http://www.boatfix.com/merc/Bullet/01/01_13.pdf

since ya got the head off. ya could go to the machine shop and have it pressure tested. or ya could put it all back together again and pressure test the whole cooling system.

or since ya got the manifold off. ya could just fill up the waterjacket and let it sit over night. i filled my waterjacket with water this was the immedite result..


that's water from the cooling jacket running into the exhust runner... by next morning. the waterjacket was empty, the exhust runner full.....

jerryjerry is right. them manifolds are expensive for sure.....

as for id. a year would help.. or
http://www.mercstuff.com/howdoi.htm
check out what drive do i have.....
from yer s/n, i suspect ya got a 1 drive.... a mcm165

Re: Merc 165, oil in water + ID question

okay.. i looked for the riser and it was kinda missing.. but how does it work on land? i thought that it only had influence when the boat was in the water..

and the manifold.. i got the same resault as the picture as ziggy posted but only with pressure on it (the 1 drop every 2 second) but nothing unpressurerised.

For the sterndrive.. i couldent read the serial nr. and the propeller i can only read 21p. i guess it means 21" pitch

and its a 17 feet boat from 1978-81

Re: Merc 165, oil in water + ID question

the s/n on the drive unreadable except for the "165"

Click to expand...

look under the 165 sticker......



unfortunetly, ya have to ruin the sticker to go look..... before ya ruin it. might let someone else confirm the s/n location...... the drive pictured is a 72 1 drive...

i looked for the riser and it was kinda missing.

Click to expand...

hum, that don't sound good. ya gotta have one of those.... how does it work? at the back side or aft part of the riser. right before it dumps into the exhust bellows that connects to the exhust pipe. on the down side of the riser is where cooling water + the exhust gases mix. then flow out the exhust system. as for working on land... it does nothing special. when in the water. the height of the riser (along with exhust shutter, aka flapper) is what keeps water from flowing back into yer manifold and engine as it rises above the water line of yer boat. therefore water can't go above the water line, unless it's pushed, like by a large wave, rapid deceleration, or going backwards fast would be a few...

if yer gonna work on yer stuff. ya really need a service manual.... ya need 3 and 4. kindly provided for us by dons.... http://forums.iboats.com/showthread.php?t=251571

yes, a 21P stamped on yer prop means a 21 pitch prop.... i spin a 19 alum. on my nineteen....... ya need to find yer wot rpms on yer boat to help decide what's right for you.....

Re: Merc 165, oil in water + ID question

hehe Ziggy i guess we misunderstood eachother the "riser" is what i call knee and yep i got one of thoose... but the shutter... im missing that one and that was the one i was asking about.

ill go look under the sticker

Great ty for the service manual link