Compression question

DGR008

Recruit
Joined
Feb 23, 2012
Messages
2
:confused::confused:
I'm in the process of buying a used boat with a 99 Honda 50 HP 4 stroke OB. I asked the selling shop to do a compression test before I sealed the deal. The salesman said the test showed 75 psi in all three cyl. I was surprised as I thought this pressure sounded very low. He said that 75 was normal in the smaller OB's like the 50 HP. I have tested compression on a 50 HP Johnson and it was in the 125psi range so I'm not sure if this should be a red flag? Any thoughts would be appreciated.
 

JB

Honorary Moderator Emeritus
Joined
Mar 25, 2001
Messages
45,907
Re: Compression question

Howdy DGR008.

Welcome to iboats. :)

I'm not very experienced with compression testing 4 strokes, DGR, but if that were a 2 stroke I would call it okay because all cylinders test the same.

Compression testing is always vague because there are so many variables. Three shops (or shadetree wrenches) can test the same outboard at different times and you would probably get three different PSI numbers, but if there were a sick cylinder all would show it and if the engine is healthy mechanically all would agree on that.

We don't know the procedure your dealer used but I would ask for a repeat test with a different gauge and maybe a different wrench.

Good luck. :)
 

Ldavidgrover

Petty Officer 2nd Class
Joined
Feb 22, 2012
Messages
197
Re: Compression question

Sounds Shady. I had a Suzuki Df 60 and the compression was 220.
 
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