84' 70hp Johnny stalling.. need help

[Challenger84]

Well today I went out fishing today with my pops and uncle.
We got to our regular fishing spot and dropped anchor for a bit.

We decided to change up spots so I pulled up the anchor and started up the Johnny.
We were cruising a bit and I decided to put down the hammer.
I was going WOT for about ten minutes and all of a sudden the RPMs dropped as if I was going at it half throttle.
We were near the other fishing spot so I limped it over there.

We were there for about an hour and I try to start the engine back up to head home and it starts right up but sounds a little different. (like the idle was lower)
As soon as I put it in gear the engine dies out.
I tried a few more times and still same results.

I gave it about 5 minutes and tried again. This time I got it in to go in gear with out stalling but as soon as I give it a little gas it dies again.

I had to try and idle back to the ramp.

I love taking my pops out fishing with me because he loves the water!

Does anyone have an idea what could be wrong with the engine?

Any and all help is appreciated!
Thank you.

 

[jtexas]

Re: 84' 70hp Johnny stalling.. need help

Sounds like a cylinder dropped out.

From the information you provided, we can narrow it down to one of 3 possible causes: compression, spark, or fuel.

First, do a compression test.
Then, spark test (not a "spark plug" test). get an inline spark tester (couple bucks at autozone), set the gap for 7/16", clip it to the engine block, attach the plug leads (one at a time) and look for a strong blue spark while cranking. If it can't jump a half-inch gap in the open air without a spark plug, it's not firing in the hole under heat & compression.

Report your results.

 

[5150abf]

Re: 84' 70hp Johnny stalling.. need help

As jtexas said you are gonna have to get your hands dirty, it really isn't hard adn all you need are basic tools.

Do as he said and get back to us, I wouldn't run the engien till you figure this out, the only lubrication the engine gets is from the oil in the gas, if one cylinder isn't getting gas it isn't getting oil either and can be damaged.

 

[Challenger84]

Re: 84' 70hp Johnny stalling.. need help

So today I check for spark and compression.

I check spark with a spark tester and all three cylinders looks good.

Compression
Cylinder #1=150
Cylinder #2=130
Cylinder #3=140

Is the compression ok?
I've heard that they should only be about 10% difference from each other.
On cylinder #2 I'm a little worried about because the compression drop 20 psi since the last time I checked it.

They use to read 150 on all three cylinders.

I took out the spark plugs (which were only in the motor for under 15hrs\3 months
I replaced all the spark plugs and fired her up.
The motor started right away and sounds like it's suppose to sound like.
I did the cylinder balance test and all three cylinders are firing!
I don't know what the problem was but it seems to be gone.
Can the coils be working sometimes on and off?
Should I replace them?

I will need to take it out on a sea test to make sure everything is good.
I will be adding a few inline fuel filters to make sure the fuel comes in the motor as clean as possible.

Can anyone recommend some inline fuel filters that has worked for them?
Thanks again for all the help and advice.

 

[jtexas]

Re: 84' 70hp Johnny stalling.. need help

Could've been a loose plug boot or something you didn't notice, but fixed during your testing.

Or could be something that can't be replicated on the muffs, only on the water.

Compression is worrisome. Did you repeat the test, just to be sure? You could try a decarb (see p.2 of the "engine faq" section of iboats). I believe I'd give serious consideration to pulling the cylinder head for inspection.

 

[Challenger84]

Re: 84' 70hp Johnny stalling.. need help

Could've been a loose plug boot or something you didn't notice, but fixed during your testing.

Or could be something that can't be replicated on the muffs, only on the water.

Compression is worrisome. Did you repeat the test, just to be sure? You could try a decarb (see p.2 of the "engine faq" section of iboats). I believe I'd give serious consideration to pulling the cylinder head for inspection.

Yes I tested the compression three times just to make sure.
I'll take it on a sea test before I remove the head.

Thanks for the help.

 

[Challenger84]

Re: 84' 70hp Johnny stalling.. need help

Sea Trail today!
Motor started right up and idled fine.
I'm thinking that the engine was flooded and the plugs got wet and wouldn't fire.

All is well again!