Johnson 150hp Outboard compression

[Swamp582]

I am looking at purchasing a 1984 Johnson 150 hp outboard. The compression of the cylinders are between 62-65 on all cylinders. I am new to boat motors and don't know what the compression should be.

 

[boobie]

Re: Johnson 150hp Outboard compression

It's way low. Try a different compression gauge before you condemn it.

 

[Joe Reeves]

Re: Johnson 150hp Outboard compression

Compression will vary with the cranking speed. The cranking rpm should be close to 300 rpm. Normally the compression on the starboard bank would be in the 100 psi range with the port bank being approximately 5 psi lower ie...... if the starboard bank registers 105, the port bank would normally register 100.

Your quoted figures of 62-65 are way too low for a 1984 V6 engine.

 

[emdsapmgr]

Re: Johnson 150hp Outboard compression

Agree. I'd be looking for compression between 95 and 100 on each cyl. Pemissible variance is 10% and your numbers are well out of that tolerance.

 

[Swamp582]

Re: Johnson 150hp Outboard compression

What kind of repairs would I be looking at to get the compression up. The engine is being sold with tilt/trim and remote control for $1000.00. Would it be worth it.

 

[boobie]

Re: Johnson 150hp Outboard compression

Check the compression again with a different gauge and follow Joe's advice.

 

[Bosunsmate]

Re: Johnson 150hp Outboard compression

What kind of repairs would I be looking at to get the compression up. The engine is being sold with tilt/trim and remote control for $1000.00. Would it be worth it.

Rebuilding the pistons/rings at the least. If you are keen to spend money and learn how to do it then it may be worth it but if you want to buy a motor and fix it up for a reasonable price then no $1000 would be far too far above its real value.