Honda 50Hp, 199 psi on Compression Test ??

[dander]

My compression test was 120 psi on all cylinders, so I thought that was great, right? Well, I looked in my Honda "official" (part # 61ZV3000E3) 3rd edition shop manual and on page 2-13 the shop manual says "14 kg/cm? or 199 psi minimum." You have to be kidding! Can anyone document that this is true? It seems to be a very high psi number. If true, I guess my motor is toast. But I tend to disbelieve it since I just had the boat up to its regular max speed with no problem..... Any thoughts?

 

[psteurer]

Re: Honda 50Hp, 199 psi on Compression Test ??

As you probably know, what is important on a compression test is that there is little variation among the cylinders. You have that for your 3 cylinders. 120 psi is great for a 2 stroke engine. But 4 stroke engines would have a higher compression ratio and I am sure 199 psi is correct (I converted 14 kg/cm? and that equals 199 psi). So here are something simple things to check first. Are you sure you gauge is accurate? Are you doing your check on a warm engine?

Here are some more complicated things that I do not know too much about but worth mentioning. Maybe someone more knowledgeable can add or correct me. Compression is related to pistons, rings, and cylinders. But I also understand compression is related to timing and valves. Have you had those checked? For my 2008 Honda 50 hp, the recommended service is a valve adjustment every season.

 

[Nick on the Bad Habit]

Re: Honda 50Hp, 199 psi on Compression Test ??

The compression test should be done on a warm engine, after the valves have been adjusted. Since the compression is equal on all cylinders and you are not having any running issues, just run it and enjoy.

 

[JUSTINTIME]

Re: Honda 50Hp, 199 psi on Compression Test ??

your fine

 

[DGR008]

Re: Honda 50Hp, 199 psi on Compression Test ??

I'm looking at buying a 99 BF 50 4 stroke. The seller did a compression check and found 75 PSI in all three cyl. I called Honda today and they also said 199 psi is the standard for a new engine but 180 and above is acceptable. The seller is a mercury dealer and says 75 psi is fine because there is no variation between the three. I don't know if it just needs to be decarboned or if I should walk/ run away? Any thoughts?

 

[JB]

Re: Honda 50Hp, 199 psi on Compression Test ??

There are too many possible variables to flatly say X-psi is minimum. Honda might, for example, specify the gauge and procedure in detail that a non-Honda dealer wouldn't know.

I suspect that DGR's dealer tested compression by rope pull, not electric with a fully charged battery with all plugs removed, for example.

Who are you going to believe, a book or a happily smooth running outboard?

 

[bitsy4643]

Wide open throttle for psi check. My 50hp 4stroke mercury shows 125 psi on all cylinders at idle throttle. Psi 205 all four cylinders at WOT. Of course engine is not running and plugs are out and grounded.

 

[GA_Boater]

Wide open throttle for psi check. My 50hp 4stroke mercury shows 125 psi on all cylinders at idle throttle. Psi 205 all four cylinders at WOT. Of course engine is not running and plugs are out and grounded.

A Merc is a Honda.

And this thread is ancient and closed.