1984 235hp Johnson 75 lbs. Compression Top Right Cylinder

[CumminsDriver]

Hey guys I got my 22ft Aquasport Center console 222 CCP A nice boat for sure, only

problem is the engine. I cleaned the carburetors out recently and put new plugs in the

engine cranks right up no problem sounds like it's ready for the ocean I hit the key

and I don't have to hold it just turn it for a 1/8 of a second when warmed up it sounds

perfectly sound.. But I did compression test on all cylinders and all were right around

80-85lbs except for the top right cylinder its a 235 V6 Johnson pretty sure its the Crossflow

not looper. I tried letting sea foam sit in for a few hours dumped it in the cyl with low compression and

cranked it up nothing happened it just smoked like hell! I only did a dry compression test no wet test and

I tried another time when it was warmed up its right at 75lbs maybe 76 and its the top right cylinder is

this maybe a problem that's happened to others before?.. I was just curious if there

was anything I should try to do or buy some chemicals to put in there before I pull the head off. I

appreciate you guys taking the time to help me out thank you!!!


Also When I rev this engine up on the muffs it sounds great revs right up nice and loud

And my compression tester is good snap on one I have 2 for that reason

 

[boobie]

Re: 1984 235hp Johnson 75 lbs. Compression Top Right Cylinder

The compression difference is with in specs. Take it out and run it.

 

[emdsapmgr]

Re: 1984 235hp Johnson 75 lbs. Compression Top Right Cylinder

Those engines with the bathtub heads normally run much lower compression than the older 235 crossflows. Normal (factory new) compression is only between 85-95 lbs anyway. You could double check the torque on the head bolts-18-20 ft/lbs. Bombardier makes an product called Engine Tuner which is excellent at cleaning carbon from the piston ring area and the combustion chamber. On that engine you can apply that product through the schrader valve on the fuel primer solenoid-pretty easy. Follow the directions on the can. Sometimes the compression will increase slightly (and idle smoother) after this an application of this product.

 

[JB]

Re: 1984 235hp Johnson 75 lbs. Compression Top Right Cylinder

I am with boobie. You are looking at a variance of 5-10#. That is within spec (+/- 15%).

If you feel you need to do something, do a decarb. That might tighten up the range.

 

[CumminsDriver]

Re: 1984 235hp Johnson 75 lbs. Compression Top Right Cylinder

Okay still waiting to get some registration money im only 17 lol but I appreciate the help a lot once I get it registered im hoping it won't just go to 3,000rpms and die I wana get that thing on plain. But any of yall know about the trims on these older johnsons I tried feeling the trim unit up with power steering fluid I've done it several times with no problems before was recommended to me by marine mechanic, just not on this model engine, I tried feeling it and pulling engine up and down about 5or7 times still nothing all I can hear is the motor running the 2 little rams will come out but the main one just won't go up

 

[emdsapmgr]

Re: 1984 235hp Johnson 75 lbs. Compression Top Right Cylinder

It is still low on trim fluid?

 

[Faztbullet]

Re: 1984 235hp Johnson 75 lbs. Compression Top Right Cylinder

I myself would be concerned as this is #1 cylinder and usually the first to be damaged if timing or cooling system problems. I have never seen carbon stuck rings in a single cylinder that the others was not effected by carbon also. The engine tuner(BRP) and power tune(Merc) is great stuff and works when sprayed directly into carbs when running.(dont think yours has schrader valve) spray about 1/2 can into all the carbs while running in water or on hose,spray 1/3 into effected cylinder and shut off, remove spark plug on that cylinder,rotate piston to TDC and empty can on top of piston so it can weep around it and let set overnite. On the trim you should never have to add fulid unless you have a leak,make sure the manual release valve is screwed all the way in...

 

[emdsapmgr]

Re: 1984 235hp Johnson 75 lbs. Compression Top Right Cylinder

Fast, you are right. That engine had the new fuel primer solenoid, but the schrader valve did not appear till 1991. I bought the upgraded valve and installed in on my older engine. Part 175158.