1987 50 hp Johnson trouble

[Radbeck]

Hi all,

Trouble with a 2 cylinder 1987 50HP Johnson.

Picked motor up as a cheap motor needing some work. Seems to start and run ok, pumps water out the pee hole. After running for maybe 5mins on trolly in idle with muffs seems to be getting very hot. (cant hold hand on heads for more than 5 secs). Did a compression check when warm and found top cylinder 130psi, bottom cyclinder 110psi dry and top cylinder 145psi, bottom 125psi wet. So about 30psi difference between top and bottom in both cases.

Does this sound like multiple problems, head gasket, cooling problem or both? How hot should it run and would I get away with the compression results?

Any further advice before I jump on in much appreciated.

[boats.net]

According to Johnson the compression just a little out of specs (15% difference max btwn cylinders) but should be ok. I would recommend removing the cylinder head and cleaning all cooling passages.

[Radbeck]

Many thanks for your reply. I'm no boat mechanic but I'm learning real fast. There is a wealth of information amongst all the forums out there and many good people willing to lend a hand. Every project I take on seems to have bigger and better problems to fix. So learning something new every time.

I've been doing plenty of reading and thought I would need to take the head off but wanted some confirmation before I went that far. The motor is unknown so probably best to have a look in any case. Was trying to avoid head removal if possible but I think I'm ready to have a go. Bit worried about snapping bolts and/or killing it permanently.

I will get myself some gaskets and attempt to get the power head out and loosen the head bolts.

Once again thank you very much for your advice much appreciated.

Cheers

[Radbeck]

Can I pull the cylinder head off without removing the power head? Or is complete dissassembly required here? Model is J50TLCUD.

Thanks

[Radbeck]

Sorry for asking again but didnt get a response.

Can I pull the cylinder head off without removing the power head? Or is complete dissassembly required here? Model is J50TLCUD.

Can you guys recommend a good manual? I'll get a few parts and have a look.

Cheers

[Radbeck]

Any ideas or further comments?

cheers

[boats.net]

Yes unless it has froze up bolts can remove head without any problems.
Go to Literature - Evinrude for manuals.

[Radbeck]

Many thanks again. I have found a manual and it is on order.

Before I do any serious dismantling I may look at water pump and impellor first. While the lower unit is off I'll also hook a hose up to water tube and run motor. Hopefully if there is a blockage this may blow it out. I may also do a decarb with Seafoam or something and see if the compression improves. With any luck I may get the motor running cooler with better compression with taking it apart.

If that fails I'll look at getting the head and water jacket cover off. Check head and clean out out water jacket etc. Replace gaskets and resurface head. Maybe replace thermostat while I'm there.

Anything else I should be looking at?

Thanks