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What should my compression be on 2003 bf20 thanks!

S

stevozz

New member
doing a full service on a bf 20 i just bought runs rough going, to try some basics first before playing with the carb ...plugs oil lower unit fluid new gas lines fuel filter etc... anyone know what the compression should be? thanks!
 
Compression for a new engine is listed as 199 +/- 14 psi.

But what's a more important consideration for a used/worn engine, because it's unlikely you will see that sort of pressure, is that the pressures are even with one another. If the lowest reading cylinder is within 10% of the highest, then the wear on the engine has been consistent for both cylinders.

Engines will lose compression as they wear and finding that compression has dropped 15% from new is fairly common.
As compression loss gets beyond 20%, the engine has a given most of what it had and is likely leaking substantially from wear.
 
jgmo said:
Compression for a new engine is listed as 199 +/- 14 psi.

But what's a more important consideration for a used/worn engine, because it's unlikely you will see that sort of pressure, is that the pressures are even with one another. If the lowest reading cylinder is within 10% of the highest, then the wear on the engine has been consistent for both cylinders.

Engines will lose compression as they wear and finding that compression has dropped 15% from new is fairly common.
As compression loss gets beyond 20%, the engine has a given most of what it had and is likely leaking substantially from wear.
Click to expand...

Thanks for your help...just curious were you got the 199 +/- 14psi number from...I came here as a last resort after looking all over the internet and it seems info for this motor is hard to come by unless I buy the complete service/repair manual for $89 thanks!
 
The numbers are from the Honda Marine BF15-20 D shop manual. Section 2, page 12. If you have an A model instead of the D then I'm not sure it would be the same spec.

As far as buying the manual is concerned, I highly recommend it if you are going to be doing all your own work. However, I've seen posts on this Forum about free copies being accessible on the web. Way harder to use but much cheaper ;>).
 
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