Mercruiser 165 4.1L trim pump leaking

[Jaywire]

Hey all, newbie to boats and the forums! I have some general automotive expereince so I can work on things. I bought a 1978 Sea Ray SRV-195 with a Mercruiser 165 4.1L straight six with the MC-1 (I think MC-1?)

We were getting ready to move it and went to put the trimp up and it wouldn't go. We put some oil in it and it trimmed all the way up, but after I stopped the pump, I heard a bunch of little spurts from the engine bay. Lifted the cover and saw oil dripping from under the trim pump and then leaking out the bilge plug hole. I'm positive it's coming from underneath and not dripping from a line, all the lines are dry.

IS there anything underneath the pump that could leak? It works great when it has oil in it, all the way up and down, so I'm sure the pump itself is fine. But as far as I can tell, there are no lines underneath the pump. Any help would be appreciated!

 

[ziggy]

Re: Mercruiser 165 4.1L trim pump leaking

i think the valve body bolts to the bottom of the pump resevoir. i think it has a big oring seal. i've never serviced mine, but i've had a drip or two like that also. my intention was to replace the oring, but tightening the bolts may have cured me to some degree.

get your service manual. maybe #3 and 4 from the adults only sticky at the top of the i/o fourm. it'll have pics and arrows for you to look at..

edit..
a pic from underneath the pump resevoir..

ya can see my leak on the upper left bolt in the pic..

 

[Jaywire]

Re: Mercruiser 165 4.1L trim pump leaking

I see... so each bolt has an oring? Or is it one big gasket type seal? Where could I get one? Boat isn't on the water yet; I'm getting it completely ready before we go out.

 

[rocket1968]

Re: Mercruiser 165 4.1L trim pump leaking

Hi Jaywire, I have the same engine, same problem (hi limewire) and what you are seeing is the result of a leak underneath the dogbone. (that piece that connects with 4 bolts.

There are 4 o-rings inside of that, and those are what is needed to replace. The botls just supply the pressure to compress the small o-rings. They are standard size and I just matched them up with a snap on o-ring kit I have.

Be very careful when retightening these bolts as it is very easy to strip/pull the threads (I did). I went with a slightly longer bolt and was able to catch enough to tighten.

 

[rocket1968]

Re: Mercruiser 165 4.1L trim pump leaking

sorry, limetime....

 

[Jaywire]

Re: Mercruiser 165 4.1L trim pump leaking

UPDATE!!!

Pulled the pump last night, nothing better to do! Voila, all 4 o-rings were crushed and also one size too big. Replaced all 4 with one size smaller and it works better than it ever has! Now my boat is ready to cruise!

 

[Kainon]

Re: Mercruiser 165 4.1L trim pump leaking

I recommend taking the dog bone off and sanding both sides with 120-200 grit paper on a FLAT surface, You'll find some distortion and a better seal. Size smaller is OK, but THICKness is Important as your looking at 500-1500PSI !!! There is a Square O-ring around the entire valvebody, they are also still available. The motors are also rebuildable at an Altenator/starter & pump motor rebuild places. (some hydraulic shops too).