Johnson 150 V6 1985 rebuild

[fdahl_009]

Hi all!

I have an Johnson 150 V6 that started to run bad some weeks ago. 90 degree V6.
It could cope with high rpm but would make very long time getting there and at all the wrong ignition advance values. Any more than 12-16deg it would not accelerate at all, and would not accept more than that even at high rpm.

One day it would not start at all. It needed 10deg cranking advance and 12 to get it to idle.
When it then got warmed up, it went at an too high idle rpm, so I needed to get the ignition down back to 4-8 degrees. Spark on all plugs, so I figured it had something to do with the mechanics of the engine.

So, have now taken the engine apart.
Have not found any big failures like melted pistons or any big damages to cylinders, but on 3 pistons the lower piston rings was stuck. Some of the other rings feels like it have lost all its "strength". Crank, rods and so on looks good.
Have found some leaks on all of the 6 "inlet boxes" on the side of the block.

Now, I have not got my manual yet, do any of you know the piston to cylinder play values?
Hopefully I am now looking at an good hone, new rings and put it back together with new gaskets and so on.


Fredrik.

 

[emdsapmgr]

Re: Johnson 150 V6 1985 rebuild

These crossflows have a tendency to buildup carbon on the piston skirts and around the ring areas. A known problem with today's fuels. Bombardier makes special products to reduce this carbon accumulation, such as Engine Tuner, Carbon Guard and their XD50 oil. Engines with carbon accumulation around the rings are hard to start, don't idle well and can lockup up at high rpm's due to pistons overheats. If you have more carbon on one side, it can be from a thermostat which is stuck open, causing that side to run cooler. The factory manual gives specs for pistons and block dimensions. You can check your parts vs these specs. If the block has more than .004 of wear or .002 out-of-round, you should overbore it. Piston diameters should not exceed .004 between measured diameters. You really need a factory manual, considering the type of work you are doing.

 

[fdahl_009]

Re: Johnson 150 V6 1985 rebuild

Thanks.
I have carbon buildup at the places the lower rings seems to be stuck.
Not very much down on the sides of the piston, a little have gone through the piston gaps of the first ring. A lot of buildup inside in the piston though, inside top.

I just wanted to know what the standard play should be, so I can measure if I need overbore or I can use the pistons that is currently in the engine..
I guess this is about the same value if I overbore.

The clymer 48-235hp manual is ordered, hope I get it next week, but if I get the numbers now, I can order parts and start the machining work..



Fredrik.

 

[wilde1j]

Re: Johnson 150 V6 1985 rebuild

Clymer and other third party manuals are junk for what you're doing. You need a proper shop manual! Good luck with your rebuild.

 

[fdahl_009]

Re: Johnson 150 V6 1985 rebuild

Ok?

Where do I get an proper version?
Somewhere on the net, or can you buy them someplace?


Fredrik.

 

[jonesg]

Re: Johnson 150 V6 1985 rebuild

clymer and seloc manuals are not good, order the johnson factory service manual.
www.outboardbooks.com