Swap powerhead? Johnson J150EXECD

[pastorbud]

[FONT=arial,helvetica,sans-serif]My Johnson J150EXECD has a compression problem. One cylinder at 95, all others 110-115. It's a 1996 . Looks like I'll have to rebuild or replace the powerhead. Hard to start and runs rough.

I'm looking at an older 225 hp Evinrude motor I can get for $250 (see pics). Seller says it's late 1980s. Can anyone help me know how far back (and how big!) I can go and still put it on my 1996 Johnson 150 looper?[/FONT]​

 

[pastorbud]

BTW, I have already asked the seller for the model and serial number, and I'm waiting to hear back.

 

[Faztbullet]

You will have swap the complete engine as the 225 powerhead wont work correctly on your 150 midsection....Got that tee shirt!!!!

 

[pastorbud]

Thanks! What about the lower unit? Also different?

 

[Faztbullet]

Lower unit will work if driveshaft is changed.....

 

[Chris1956]

J150EXECD is a '98 motor, FWIW.

 

[pastorbud]

Thanks. Learned something new!

 

[Chris1956]

Gee, lowest compression is 95# and highest is 115#. Sounds like you are just in tolerance, for an older motor..(smile)...

Check the carb bowls for warping, replace if warped. Clean the six carbs and install new kits. Since she runs rough, you should pull the throttle bodies and give them a good cleaning.You can remove the side covers and blow out the throttle bodies with carb cleaner and install new cover gaskets, without removing the idle needles.

Install new Champ QL78YC spark plugs and new thermostats, if original. Waterpump is good?

 

[pastorbud]

Y'know, I've kinda gone 'round and 'round about that. I don't know for certain that I've gotten an accurate pressure test. I posted a separate thread on it. Lemme see if I can find it.

 

[pastorbud]

Well, I can't find the thread. Anyway, the problem is, when I try to do a compression test, two of the cylinders behave oddly. I turn it over with the plugs out, the carbs open, and the ignition grounded.

On two of the cylinders, when the pressure gets up to about 110-115, the starter Bendix disengages. The motor almost seems to be kicking over, like it's trying to start...which is, of course, impossible.

I cleaned up the Bendix and reduction gear, lubed them, even replaced the starter. Same result.

So, I don't really know what those two cylinders would go up to. The starter disengages at 110-115 pounds.