1985 150hp Johnson

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ramctd2003

Recruit
Joined
Jun 5, 2006
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2
I have a 1985 Johnson 150hp V6 model# J150stlco<br /><br />It will run just fine and when it gets warmed up the power goes way down. It will idle just fine. <br />When it cools down it will run for a while and then do the same thing. I have a boat repair shop here that says it needs a new powerhead. <br />I find that hard to believe because it will run just fine when it is cool.
 
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GatorMike

Ensign
Joined
Aug 3, 2003
Messages
902
Re: 1985 150hp Johnson

A small investment of 30 bucks or so will buy you a compression gauge. Then in 5 mins you can do a compression test yourself. This should tell you if you have a good powerhead or not. If the compression is fine I would look at the powerpack next. But better not go stricktly on my advice I am only a novice you might want to wait on the experts to respond.
 
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Walker

Captain
Joined
Jun 15, 2002
Messages
3,085
Re: 1985 150hp Johnson

Sounds like it may be overheating after running a little while. when was the waterpump and thermostats last serviced. Do the compression test.
 
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wilde1j

Vice Admiral
Joined
Apr 15, 2002
Messages
5,964
Re: 1985 150hp Johnson

If the compression is OK, find yourself a new repair shop, BC they haven't a clue.
 
Melvin Hatcher

Melvin Hatcher

Petty Officer 2nd Class
Joined
Sep 16, 2003
Messages
181
Re: 1985 150hp Johnson

I have a 1985 XP150 Evinrude, which is essentially the same motor as yours.<br />I have replaced most of my electronic to get my engine back to life.<br />Stator, power packs, voltage/regulator, and two coils.<br />After twenty one years the electronic kind of goes to pot. ;)
 
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ramctd2003

Recruit
Joined
Jun 5, 2006
Messages
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Re: 1985 150hp Johnson

The compression in all cylinders is between 95-100. I am getting the boat back soon, and I will start to look for the electrical problems. <br /><br />Thanks for everybody's input.
 
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emdsapmgr

Supreme Mariner
Joined
Dec 9, 2005
Messages
11,551
Re: 1985 150hp Johnson

Compression sounds just fine. Time to check out the electrical and cooling systems. Take a timing light to the lake next time out. When the power starts to go down, hook up your timing light and check each of the 6 spark plug leads for strong, constant spark. Also, the engine should warm up to 143 degrees. You should be able to put your hand on the block/heads for 15-20 seconds-when warm. If it is too hot to touch, you need to look at the cooling system.
 
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sterudpa

Cadet
Joined
May 27, 2009
Messages
15
Re: 1985 150hp Johnson

I am looking at buying a boat with a 1985 johnson VRO on it. the compression tested between 85-90 on all the cylinders. is that a decent range or is this motor almost dead?
 
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