replacing 1986 Johnson 175 block with 1988 Johnson 150 crossfire

[macfamily]

I have just blown a cylinder in my 1986 Johnson 175, needs further investigating probably carb or reed valve fault. I am looking for a replacement block. I found a 1988 150 Johnson crossfire will it work?
Thank you,
Joe

 

[Joe Reeves]

Re: replacing 1986 Johnson 175 block with 1988 Johnson 150 crossfire

The 1986 175hp and the 1988 150hp are both "crossflow" engines, however the exhaust baffle setups are quite different and will not interchange without extensive work and replacement of other engine components.

For the 150hp powerhead to fit, you would need to (on your present engine) remove the lower unit and powerhead, then remove the long exhaust housing from the steering swivel bracket assembly, after which the 175hp adapter plate that the power head sits upon would need to be replaced with the 150hp adapter plate, the megaphone, various gaskets, etc.

It would involve a tremendous amount of work..... not simply a case of dropping the 150hp powerhead on your existing engine and bolting it down.

 

[macfamily]

Re: replacing 1986 Johnson 175 block with 1988 Johnson 150 crossfire

I have just blown a cylinder in my 1986 Johnson 175, needs further investigating probably carb or reed valve fault. I am looking for a replacement block. I found a 1988 150 Johnson crossfire will it work?
Thank you,
Joe

Thank you, I think I will keep looking for a better match. do you have any suggestions on a replacement?

 

[reeldutch]

Re: replacing 1986 Johnson 175 block with 1988 Johnson 150 crossfire

its probbebly cheapest and easyerst to rebuild your block if its in good shape otherwise.

 

[macfamily]

Re: replacing 1986 Johnson 175 block with 1988 Johnson 150 crossfire

My damage is to extensive .020 , it would leave the finished cylinder wall too thin, or are you suggesting re sleeving the block?

 

[Joe Reeves]

Re: replacing 1986 Johnson 175 block with 1988 Johnson 150 crossfire

Just for your reference..... Reboring to .020 is a common practice, even boring to .030 or .040 is done quite often with plenty of cylinder wall left.

 

[macfamily]

Re: replacing 1986 Johnson 175 block with 1988 Johnson 150 crossfire

My mechanic told me going to.040 would cut down on the engine life and not worth the cost.

 

[macfamily]

Re: replacing 1986 Johnson 175 block with 1988 Johnson 150 crossfire

The engine block has already been bored to .020 plus need to do another .020 if even enough to cover damage would be .040.

 

[G DANE]

Re: replacing 1986 Johnson 175 block with 1988 Johnson 150 crossfire

On most crossflows i've had apart, the sleeve is like 1/4" thick, hard to imagine removing another 0.020 would hurt anything. Besides from that, since OMC makes the 0.040 pistons, everything must be fine, whichelse purpose should it have. Is the mechanic the one that quoted you the 150 block ?

 

[Joe Reeves]

Re: replacing 1986 Johnson 175 block with 1988 Johnson 150 crossfire

Resleeving the block is also a common practice, bringing the bore back to the standard bore size.

 

[Faztbullet]

Re: replacing 1986 Johnson 175 block with 1988 Johnson 150 crossfire

my 1986 Johnson 175, needs further investigating probably carb or reed valve fault. I am looking for a replacement block. I found a 1988 150 Johnson

If yours is the bubble back 175 it is a big bore(3.625) and the 150 is a 3.500 bore. If its a flat back 175 all parts you have will work. If its the bubbleback it would require 6 new pistons to fit the 150 block along with other parts Joe listed. You Mechanic is correct if it the big bore as this engine has 1/8 inch sleeve from factory and .040 is max block can be bored. This leaves a really thin sleeve and the engine really susceptible to damage from even a minor overheat.

 

[macfamily]

Re: replacing 1986 Johnson 175 block with 1988 Johnson 150 crossfire

would you recommend a company that re-sleeves outboards?
Thank you all this has been very helpful.

 

[Joe Reeves]

Re: replacing 1986 Johnson 175 block with 1988 Johnson 150 crossfire

Call various machine shops to inquire if they do outboard engine powerhead machine work. If so, they should be able to do the resleeve procedure.

 

[Faztbullet]

Re: replacing 1986 Johnson 175 block with 1988 Johnson 150 crossfire

If you have to replace more than one sleeve find another block as sleeving aint cheap. I charge $300 a hole and that includes: sleeve, porting & chamfering, light milling of cyl
deck, boring and honing of cylinder to size.