compresion

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fishingrv

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I'm looking to buy a 1996 v20 with a 150 johnson ocean runner.They tell me that the compression is 82 to 85 in each piston. Can someone let me know if that is good. Thanks
 
fishingrv said:
I'm looking to buy a 1996 v20 with a 150 johnson ocean runner.They tell me that the compression is 82 to 85 in each piston. Can someone let me know if that is good. Thanks
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Some of the guys better versed than me will be along and confirm those numbers or not...but one thing you want to be sure of is that all the numbers are consistent w/each other...they should not vary more than 10 lbs or LESS


Plus...drain a small sample of foot-oil from the lower screw...if excessive metal filings are present it may soon be in need of repair...

Good luck w/it...let us know what ya did and show us some pictures if ya get it...
 
Like Reel, others will have better information about the compression, but just from reading all the previous posts on that subject those numbers sound low. Good advice from Reel regarding checking the lower unit fluid. It should be clear and clean. If it is "milky" looking there are bad seals.
 
that's a worn out motor should have more compression than that, more like 95 up in compression. i'd steer clear or plan a new set of rings for it. it must have a ton of hours like in the 3500 to 4000 hr area.
 
Skools Out said:
that's a worn out motor should have more compression than that, more like 95 up in compression. i'd steer clear or plan a new set of rings for it. it must have a ton of hours like in the 3500 to 4000 hr area.
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either that or your gauge is broken, i dont see a carbed engine lasting that long. but hell you never know.
 
cehck it with another guage, I have four or five compresion guages, teh most expenisve one I own reads 10 psi low, the cheapest one reads 5 psi high( I checked than against a high doller set of liquid filled German manufactured pressure guages). Usually if they are close to each other, they are OK. I've never seen an engine equally worn out on all cylinders, usually, one cylinder lets go first. But I guess it cousl happen. Take the boat for a spin, see if it turns up rpm(check your tach also)
 
it sounds like one of the twin 1990 Johnson 140's i bought from BR that had according to the hr meter 3890 hours on it. that motor reads between 62 and 68 psi on all cylinders it actually runs just hard to start at times.
 
I've got a '84 150 Johnson and the compression was around 85-88. They told me that it was "worn out" but, she runs like a clock. 30mph@5200rpm . She could blow any day, but heck we'll use 'er 'till she dies:party: For $2500.00 boat motor and trailer I couldn't go wrong... and I know......:thre:
 
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