Johnson 150 reinstalling pistons

[fountainboater]

I have rebuilt many small block and Big Block Chevrolets over the years, but I am rebuilding my first outboard, a 1993 150 HP looper, and have a question. In the seloc instruction manual it says you have to use a special tool to center the rod on the crankshft before you tighten it. How important is this, and is it something you can eyeball or not. If it is a critical step, does anyone know where to get the tool to do this? Any help will be appreciated.

 

[reeldutch]

Re: Johnson 150 reinstalling pistons

dont eyeball it use a pick to feel any edges.
remember that your bearings will feel the same thing on the inside, only at 5500 rpm.
so you understand it wil eat your bearings if its not right.

make sure its smooth. if you cant get it right i would use the tool if its still not right buy a new connecting rod or it will eat a bearing and destroy your crank.
be very patience and torqeu it down in at least 3 steps to get it down straight.

good luck

 

[fountainboater]

Re: Johnson 150 reinstalling pistons

Thanks for your response. I was obviously confused. I thought they were referring to centering the rod itself on the crankshaft journal, and not the cap on the rod. That clears up a lot. Thanks again

 

[reeldutch]

Re: Johnson 150 reinstalling pistons

no problem

i rebuild my 150 93 a few years ago.

whats the reason it blew up?

 

[fountainboater]

Re: Johnson 150 reinstalling pistons

The #1 and #3 cylinder look like they leaned out and the rings stuck. It lost compression in those two cylinders and galled the cylinder slightly. I bought the boat really cheap because of this. I had those two cylinders bored .030 over and am putting new pistons in those cylinders. When I took the carbs apart I noticed some trash tha was clogging the main jets in both of those carburetors, so hopefully that is what caused it to lean out. The rest of the motor looks fine, and it would still start and run when I got it. Wish me luck, I need it.

 

[daselbee]

Re: Johnson 150 reinstalling pistons

http://www.marineengine.com/discus/messages/12478/294341.shtml

More on this here.....

 

[reeldutch]

Re: Johnson 150 reinstalling pistons

i had basicly the same problem with mine 93 60* OIS.
i put everything back together motor started right up.
let her run for a wile and started coughing.
so i checked the timing and linc and sinq everything was good still coughing.
checked for crancase seal leak couldnt find it.
than i sprayed some carbcleaner around the intake manifold and the engine reacted.
found out that the trothle body shaft were the butterfys are on was leaking air.

i changed the trothlebodys and carbs with a later model that has adjusteble idle screws and runs like a champ now without any hickup.

just someting to keep in mind took me a long time before i found it.

 

[fountainboater]

Re: Johnson 150 reinstalling pistons

That is certainly something to remember. This motor doesn't have many hours on it, so I think the throttle body shafts should be fine, but I'll certainly check them out. Did that leak have something to do with the failure of your motor?