1981 25hp mariner lower unit

[skinnywaters]

ok, riddle me this...just picked up an 81' 25hp mariner (yamaha made though). lower unit had bad oil seals. took it apart and replaced the seals. did an air pressure check and it most certain held pressure. actually blew the top seals out like a champagne cork. Re-set the top seal housing and put the lower unit back on. Dropped it in the barrle and guess what, milky oil almost right off the bat. Now, did see the milk draining out of the weep hole in the bottom where the gear control arm would be entering the interior gear housing. I can not find a good exploded diagram of the lower unit, but i assume that there is a seal down there also since water does get down there. how the hell do you get to that seal? do i have to take the whole lower unit apart?? and why did it allow so much pressure with the air and not leak or gurgle?? can anyone help me?

 

[Faztbullet]

Re: 1981 25hp mariner lower unit

You are only supposed to put about 15 psi of air in unit but you also have to vacuum check it. The shift rod has a boot around it and it may have split from too much air pressure

 

[skinnywaters]

Re: 1981 25hp mariner lower unit

i actually read that about the 15psi after we did it but when we did do it we turn down the compressor to like 20-30psi. the boot, can i inspect it or change it without taking the whole thing apart? thats the problem, i am new to this motor and i cant find any good exploded schematic. selco seems to be the only one that make a manual and it does not read well nor have the best schematics

 

[carholme]

Re: 1981 25hp mariner lower unit

skinny;

What is your s/n?

Here is a link to the Mariner 25 you want and you can look under Gear Housing for the exploded view:

http://www.crowleymarine.com/mercury-outboard/686.cfm

Here is a link to Mariner manuals for which you will need your s/n:

http://www.marinepartsman.com/Mariner-outboard-manuals_2.html

Gerry

 

[skinnywaters]

Re: 1981 25hp mariner lower unit

Thanks Gerry!

I found the problem on Sunday. Who ever did work on the foot last had the shift arm boot on all wrong. After a couple of tests and oil flushes, I have it sealed and clean oil. Dropped it on my boat and ran it down the river yesterday and everything seems good...with the foot that is...now im scratching my head over a fuel issue. HA! gotta love a project! I have a 76 evinrude 35 that had this same issue. Hoping that the fuel pump just needs to be rebuilt (normally an easy fix). But it seems odd because it seems that the issue is in the ball, becuase it wont hold pressure. The boat was running great and then just died like it ran out of gas. Turned around and sqeezed the ball and it was empty. It is a brand new line and ball. On my 35, i found a pinched fuel line to my carb, but all these lines seem straight and new. I still don't know how the ball lost pressure with a pinched line past the pump though. Im feel like im going to be a professional outboard rebuilder someday, like it or not