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1985 GT 150 stopped running

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funmoneypit

New member
Hi all, '85 GT 150. We were running close to full throttle and the motor just stopped. Tried to start it and the motor wouldn't hardly turn over. My son put the trolling motor in the water and started toward the dock. A minute later I tried to start again and the motor fired right up. We weren't far from the dock so never got up on plain but the motor seemed to run fine.

Seems electrical. What do you guys think? I am going to take the cover off this morning and check connections.

TIA
 
racerone said:
Tested your overheat horn?-----Do a compression test and post your numbers here.
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I haven't done either. I do know the spitter had a nice flow of water.

If it was compression, I wouldn't expect it to just die, then be hard to crank like a low battery (turned over very, very slowly) and then two minutes later fire right up and run great but I could be wrong.

I'll check those items this morning.
 
Water pump impeller needs to be changed every 5 years!-----I can not see , hear or feel your motor.-----Up to you to do the investigating.----Should not be hard to figure this out !!-----The tell tale water does NOT go through the engine.----And good flow from tell tale does not indicate proper cooling !!!
 
Well I found a problem but it seems it has been a problem for a while looking at the spark plug.

Overheat horn works as it should.
Compression is 80 - 88 on all cylinders but the lower starboard hole has zero compression. I will take off the head but does this usually mean the motor is done? I am guessing it has been running like this for a long time.
Pic isn't the greatest but it looks pretty bad.


20230722_101335_resized[4812].jpg
 
There you go.----Pull cylinder head.----You may not like what you see.----Every one of the crossflow motors will suffer from broken piston rings.----Worthwhile to rebuild if you can do the work yourself or spend $18,000 on a new motor.
 
racerone said:
There you go.----Pull cylinder head.----You may not like what you see.----Every one of the crossflow motors will suffer from broken piston rings.----Worthwhile to rebuild if you can do the work yourself or spend $18,000 on a new motor.
Click to expand...
Thanks, figured a broken ring before I ever took the head off. I have to get in there with a flashlight but haven't seen anything obvious yet. There is a little scoring on part of the cylinder wall but it is just in one spot and doesn't go up and down following the path of the piston. It still runs great though even though it's on 5 cylinders. I am still not sure what happened yesterday when it just quit but then started back up after two minutes.

I have had this boat for 13 years. It's been a great boat with very little problems but not sure it's worth putting money into it (it's 1985 also). Do you know of a good tutorial/videos of the rebuilding process (I'll search YouTube)? I used to drag race and have rebuilt many car motors. Any ballpark estimate of parts cost?

Again, thanks for your help.

ETA: I do have the repair manual.
 
faztbullet said:
You will need to measure bore and replace all pistons....$2K will fix it
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Thanks for the reply.

Does your estimate include boring the cylinders? The zero compression cylinder has basically extra metal that is almost welded to the cylinder wall. It is actually humped up instead of gouged. Wondering if it isn't actually part of the ring that let go although that seems strange.
 
Does your estimate include boring the cylinders?
Click to expand...
Yes as boring should not be more than $65 a hole. Make sure who does it has done a Johnrude block, as it has to be bored all the way to the bottom of block. If not it will leave a step that piston skirt hits
 
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