Compression reading/ 1987 Force 50hp

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Sonny4102

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May 27, 2009
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I have a 1987 Force 50hp outboard on my 14' Bayliner. I was wondering what the proper compression reading should be. I am getting 120/120psi. I wondered if it also may be related to my runnability issue. It runs fine out of the water on the muffs, but under a load it won't rev out. I found some parts in the carb that need to be replaced but this is the first time I checked compression. Please let me know if you have any thoughts.

Thanks
 
Jeremy90bay

Jeremy90bay

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Re: Compression reading/ 1987 Force 50hp

I have a 1990 50hp. I was told anything over 120was good. mine is at 125/125. dont know if this helps you. I had the same issue and had no spark to 1 cyl. have you checked spark.
 
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Sonny4102

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May 27, 2009
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Re: Compression reading/ 1987 Force 50hp

That makes me feel better about the compression. I had spark on the muffs, but I did not check in the water. It seems to rev up in neutral but not under a load. I will check the spark once I rebuild the carb and get it back in the water.

Thanks for the info
 
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portwill363

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Jun 11, 2009
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Re: Compression reading/ 1987 Force 50hp

My 89 Force 50 is 125/125 also. However the book says 140-160 is what it should be. My motor does run good so i did a decarb and perhaps it is better now.
 
Jeremy90bay

Jeremy90bay

Petty Officer 1st Class
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277
Re: Compression reading/ 1987 Force 50hp

I read on a post some where here that you get a higher compression at WOT but im not sure how true this is. I only tested mine in nuetral.
 
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potminer

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Jul 19, 2009
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Re: Compression reading/ 1987 Force 50hp

I have a 1990 50hp force & the comp on mine was 150/150psi. I would be comfortable with 120/120psi. So long as they are close(within 10%).
 
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actionpaintball

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Jul 4, 2009
Messages
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Re: Compression reading/ 1987 Force 50hp

You can get some variances in the readings just in how your take your compression. But as long as you spin the engine at the same speed and are tightening the test port o-ring and not changing your test procedure-you want to be within 10% as mentioned above. Lubrication can change your reading 5-10 PSI as well (fogged wet or "dry" test).

I would just run a normal decarb and soak for 24 hours and re-test. I would have no problem living with 120+ PSI as long as all cylinders were close (roughly 10%).
 
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foodfisher

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Feb 18, 2009
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3,756
Re: Compression reading/ 1987 Force 50hp

Compression-OK. Won't pull a load, start with fuel supply.(carb, sync,pump,vent)
 
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foodfisher

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Joined
Feb 18, 2009
Messages
3,756
Re: Compression reading/ 1987 Force 50hp

Compression-OK. Won't pull a load? Start with fuel supply.(carb, sync,pump,vent) Oh yes, a veteran addict said to check sparkplugs. Most likely and most easy.
 
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