1976 90hp 6, low compression in one cyl.

[hilljack]

Great site! Tons of helpful info.<br /><br />I bought a boat needing a water pump, the old one went bad on the previous owner. I did a compression test and it indicated a problem with the (#5) cylinder, 45 psi. I haven't had the chance to take a look yet, but if it's a stuck ring is it possible to pull that piston out leaving the crank in place? I know I need to re-hatch the bore but I'd like to know if that's the problem before I get too far into the job. <br /><br />Thanks in advance.<br />HJ

 

[Laddies]

Re: 1976 90hp 6, low compression in one cyl.

Mercury inline engines all mest have the crank removed to pull a pistion as the do not have cyl. heads

 

[hilljack]

Re: 1976 90hp 6, low compression in one cyl.

Thanks for the speedy reply Laddies. I was hopeing there'd be enough room to manuver the rod and piston out around the crank. I'll have to bite the bullet. Should I just leave the rest of the rods/pistons in their bores and just pull the rod caps off?<br /><br />HJ

 

[Laddies]

Re: 1976 90hp 6, low compression in one cyl.

Get a manual the crank with all rods and pistons attached is removed in one unit and reinstalled as a assembly you will need merc ring compressers, two people with alot of care can do the job with out them, but I certainly wouldn't recommend it as a good service practice--Bob

 

[Clams Canino]

Re: 1976 90hp 6, low compression in one cyl.

That , and you outta re-ring them all and replace the end-cap seals while it's apart anyway.<br /><br />-W

 

[hilljack]

Re: 1976 90hp 6, low compression in one cyl.

Thanks for the advice. Yep, it's looking like I will go through the whole thing. I was mainly trying to buy some time until this winter. The manual doesn't give many options. I'm a firm believer in doing things the right way, I was curious what others had tried.<br />Thanks again,<br />HJ

 

[timmathis]

Re: 1976 90hp 6, low compression in one cyl.

You sure can take what laddies&Clams has told you to the bank! they are 2 of the best marine tec's out there.. That story about it needing a water pump, Goes to show you how it can be in the real world. <br /> For a lot of lot of you newbie's out there before buying a motor a compression tester,volt meter and knowledge that you can find here at iboats. Is some of the best insurance that you can get when it comes to buying a boat motor etc.<br /> I thought this is a little valuable information for some of our new fellow posters and or viewers to know!!<br />Thanks, Tim Mathis<br /><br />P.S. To Clams or Laddies (Or any of you pro's) Please throw in your Million dollars worth!!!<br />That was my 2 cent's worth! Tim