72 50hp seahorse falling on its face

[Freddyb18]

Hello!

I recently had a problem getting the motor started in the water. After replacing some parts in the starter, I took it out and it ran like a dream. I took it out a second time and we got about 1/2 mile out and the motor shut completely off at WOT. We had some suspicion that there was an issue with spark when we were working out the issues with the starter...

We waited about an hour and the motor started again. We got it back about 1/4 mile or so and it died just above idle.

Could this be an over heating issue? I have the flywheel removed right now, I was looking for bare wires or a bad connection.

Any help would be appreciated.

Things I have replaced/repaired: impeller, fuel lines throughout, starter, plugs, rectifier, starting battery, carbs rebuilt

 

[Freddyb18]

Re: 72 50hp seahorse falling on its face

Could a bad thermostat behave this way? This engine has been sitting for the last 10 years or so, that is what the previous owner told me.

 

[nphilbro]

Re: 72 50hp seahorse falling on its face

A bad powerpack can cause you to lose spark on all cylinders instantaneously since it is the simple "brain" linking the trigger, stator and coils. I'm not sure how sensitive to heat they are but that is one sure thing that will kill spark. If the motor warmed up enough it might have allowed some small internal connections to soften and move.

Assuming the starter is turning fine, you should be able to check spark with just a few turns of the key - it will either be there or not.

If it's a problem triggered by heat from the motor due to its proximity you might be able to recreate it using a hair dryer aimed at the power pack with the cover off. Warm it up and check for spark again. If there was spark the first time and none the second I think you have your culprit. The only thing that will be hard to bench test is the effect of vibration while the PP is warm/hot. Circuits that are cold soldered are very susceptible to heat and vibration. Since it is at least working intermittently, for once, this might help you diagnose more easily.

I saw recently on another thread where exhaust was coming into the cowl. That would create immense heat on the components as well.

Just my 2 cents after spending 3 weekends straight troubleshooting and finally replacing all the components of my ignition system one by one.

 

[nphilbro]

Re: 72 50hp seahorse falling on its face

I forgot to also mention to check ground wires. These are all quite visible. Unscrew/bolt them and sand away any rust and corrosion from the contact points and make sure there is a good current pathway where they connect at the block- ie. be sure paint, grime, etc isn't obstructing good contact. Be sure the wires are in decent shape and replace if they are suspect. You can buy a roll of 14-16ga stranded ground wire for about $8 at any Radio Shack or auto parts store. Sitting that long condensation is likely to have some impact. This is an easy remedy and one that should probably be done whether the motor is running well or not.

While you have the flywheel off, is there any rust on the magnets? That's the only iron on the entire part. If so, use a fine grit sandpaper to remove it. I'm sure that's not your main problem but it's something preventative to do with the FW already off.

There is also a ground wire coming off the power pack- it's probably the bottom right one. Be sure to check that.

If you want any motor to do weird things - mess with the ground!

 

[boobie]

Re: 72 50hp seahorse falling on its face

If you don't have the equipment to check out the ignition system complete, my first "guess" would be a bad power pack.

 

[JDusza]

Re: 72 50hp seahorse falling on its face

Just curious.
Why did you wait an hour?
Did you diagnose out high speed fuel delivery?
J

 

[Freddyb18]

Re: 72 50hp seahorse falling on its face

nphilbro - I plan to closely inspect the power pack in the coming days. Best price is $110, so not the cheapest thing to replace. I will go through my ground wires and be sure that they are grounded. If I don't find any improvement afterwards I may find myself replacing it.

@JDusza - We tried to get it to start again, but it seemed like we were not getting spark. We decided to wait for a bit and do some fishing (it's been a long time coming, a couple months of takin' her to the water just to see her fail in one way or another...) The high speed jet did not seem to have much of an adjustment to it if any. I was very careful when putting the carbs back together. I am not a pro by any means, if it was a high speed fuel delivery problem, it seems like the motor would not have much of an issue starting back up after our initial failure, maybe we would have to run it at low speed, but it would have started back up.

THANK YOU FOR THE REPLIES!!!! KEEP EM COMIN' !!!! ILL KEEP YALL UPDATED!