MC-1 trim parts help '78 Mercruiser 165 I6 Serial Range 4940000

karbine98

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Mar 17, 2014
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Overpressured trim system while pulling in arms to reattach to lower unit after impeller service, etc and developed leak at base of reservoir. Finally got pump out----hideous task with almost totally inaccessible transom mounted bracket bolts. My more nimble son finally got back one off. Couple questions please:
1) Leak not from hose, but from seal above it--either the res cover seal or the seal on the manifold(?) mounted on bottom of the reservoir that goes down to the transom plate outside. Seal is no longer available from Merc.
A) What should I use on cover and the part the hyd line comes out of?
B) If I have cracks in the bolt holes in the reservoir is there anything I can use to seal/repair?
2) Since I can imagine needing to be able to remove pump/res assembly in the future to refix it, etc, can I reinstall it using a mounting bracket like I see used on newer models? There is a nice big space on the deck just below where it was mounted that looks as though it had a bracket at one time. Prev owners had engine replaced and maybe it came with the transom mount and that was used. Who knows, but I don't ever want to go through the miserable job again trying to remove trim pump.
A) I see the brackets for sale. Are they fairly universal and would my old Prestolite pump/res mount to one ok? Pretty sure I can cobble something to avoid using the original bracket.

As long as I had fluid in reservoir, my system worked fine. I think it had been leaking, maybe only intermittently, so I was probably going to have to do this anyway. Had only had it out 4 time last Sept after buying it. Man am I ever learning the ropes of being a boat owner--mostly the hard way, but so what I love it. Thanks for advice. Greg
 

Bt Doctur

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Aug 29, 2004
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Re: MC-1 trim parts help '78 Mercruiser 165 I6 Serial Range 4940000

The plate with the screws has a O ring type seal.There is no pressure in the res so a bead of silicone should work. just apply to the base
and let cure first, then install base. Kind of make your own o ring seal. The valve body itself uses 4 small O rings for seals, available locally at the auto parts store or air conditioning store.
 

Bt Doctur

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Re: MC-1 trim parts help '78 Mercruiser 165 I6 Serial Range 4940000

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karbine98

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Mar 17, 2014
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Re: MC-1 trim parts help '78 Mercruiser 165 I6 Serial Range 4940000

Ahhhh....I see. Thanks lots. Don't know why it seems to take me forever to learn the correct names, ie the valve body and gear assembly. Knowing that that is more than just a cover or lid for the reservoir opens even my pea-brain. What do you think of mounting it to a deck mounted bracket that can be easily accessed? Advice appreciated. Greg
 

Bt Doctur

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Aug 29, 2004
Messages
19,111
Re: MC-1 trim parts help '78 Mercruiser 165 I6 Serial Range 4940000

I know exactly what your talking about ,bolted to the rear mount. Simply make a bracket and mount the pump .
 
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