Please help! 1984 Johnson 90 hp 2 stroke j90mlcrd

[Tomer9764]

I bought this motor July 2012. Ran great. Used it all season with no problems. It was used in salt water, yes I know, but it ran good and i have only used it in fresh water since. The bolt heads are rusted and the grey coating is flaking off on both the heads and I'm guessing what would be head covers. I'm thinking overheating, saltwater corrosion or both. I didn't know much about boat motors and at the time and seemed to be doing ok. I winterized it late fall and I mean October in Maine, ran fine. Added stabil to gas in tank ran motor until warmed up and sprayed fogging oil directly into carbs. This did not stall the motor so I shut it off, removed spark plugs and filled the cylinders with fogging oil and reinstalled plugs. Keep in mind I screwed up and left it with a half tank of gas all winter I'm hoping this is the reason for the steam. I made sure to store the motor perfectly plumb to the ground so it could drain.

I started the motor today for the first time since winterizing and it ran like crap! Blew severe smoke for about 7 minutes, fogging oil I'm sure. The smoke cleared up, it still idled like crap for another 5 mins and I noticed the pee stream would stop for a moment and then spray again. After this happened a few times over a 2 minute span I jumped out of the boat and put my hand under the flow. It was cold, stopped, came out again scalding hot, stopped again then came out cold yadda yadda. The heads were getting too hot to touch so I ran to the controls and shut her down. She peed out warm water for a second then blew steam out through the tell tail like I've never seen. I then decided to pull the plugs one at a time and do a compression check. Steam poured out from both bottom plug holes but not the top ones. Water in gas I hope. Compression was 110 psi in three cylinders and 109 in the bottom right. The plugs were soaked in oil. It's impossible to get a boat looked at around here due to over booking. And not much to look at online as far as this johnson motor goes. Any ideas? I hope I didn't blow this powerhead.

Thanks

 

[coolbri70]

Re: Please help! 1984 Johnson 90 hp 2 stroke j90mlcrd

did you replace the impeller? the thermostats? are you running on muffs or in water? i gave up on the muffs, use a large tote now, works better dunked. the compression sounds ok, replace or clean the wet plugs, may be from the fogging oil. did you literally fill the cylinders with fog oil?

 

[emdsapmgr]

Re: Please help! 1984 Johnson 90 hp 2 stroke j90mlcrd

That engine overfuels slightly at idle-not unusual for the plugs to be black and look somewhat wet. It's when you are running WOT that they turn light tan. I'd be concerned about the overheating. Easy way to check. Borrow/rent a laster temp gun. (local auto part stores rent them.) Fire the engine on the trailer and garden hose. Check the cyl heads for running temps. That engine should idle between 143-155 on the garden hose. It should have a constant, strong telltale stream. Check to make sure the telltale hose is not plugged with debris, sand, etc-a common problem if the engine is used in shallow waters. Since the engine is recently new, it's possible you have no maintenance history on it. If so, probably best to replace the water pump impeller. That way you know it's not going to overheat when out on the boat this summer.

 

[91 Sprint]

Re: Please help! 1984 Johnson 90 hp 2 stroke j90mlcrd

Good Day! you said you were getting hot then cold sounds like you also need a T-stat and pressure relief change out too!
best of luck!

 

[Tomer9764]

Re: Please help! 1984 Johnson 90 hp 2 stroke j90mlcrd

Good Day! you said you were getting hot then cold sounds like you also need a T-stat and pressure relief change out too!
best of luck!

Thanks for the info guys. I was also told the thermostats might be stuck due to corrosion and sitting all winter. I was told they are a nightmare to change on this motor. Going to have someone take a look at it tomorrow and see what they can come up with. I hope I didn't heat it up too much!

 

[Fleetwin]

Re: Please help! 1984 Johnson 90 hp 2 stroke j90mlcrd

Nightmare yes, depending on your perspective.

Allow a lot of time and patience.

Drop the lower engine cowl pan, as far as you can, and get yourself some nice 1/4" socket swivels. Can be done with above.

While you're at it, remove the head covers and replace the "divertors".

PATIENCE.