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Testing a coil

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A4effort

A4effort

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Not familiar with boats so much, but based on my experience with car motors, if you get a couple bad coils, the rest are pretty quick to follow. Is that true with this 240HP V6 EFI Merc?? Is there a way to test them?
 
I get it, this question has already been answered....I just want to test them on the bench with an ohm meter and not drag the boat to the gulf unload it, test it, load it back up and drag it back home..... But testing on the bench doesn't tell you what they are doing under load....I get it. I'll stop whining now.
Just having a little chat with myself...lol
 
If you can find a Merc Manual that will give you the data you are after. The Merc setup is considerably different than the Seadoo setup.
 
Testing a Merc coil isn't like doing an old car. The coil packs have a CDI built into them. You really need to get you hands on the manual. But, Coastie may be nice enough to post the chart.
 
Put two new coils in for a total of 4 new ones and it is still shutting off. I moved them around trying every spot and still shutting down at high rpm's. It is much improved over the 5mph top speed. New symptoms or should I say more noticeable now symptoms are surging continuously at WOT , won't go over 40mph, usually stuck at about 35 and of course the ever impressive shutting off at the higher (5k) rpm's. Always starts right up and takes off again..., shoots right back up to 30 mph and then surges its way to 35.....
Maybe trigger??stator??give.....mercy
 
I would be looking at the fuel system. Normally when you get surging, you are running out of fuel. SO... that generally reviles plugged up filters.


But, there is a little device that's called the Throttle Guardian. It's in the helm, and the will cause the same issues when they go bad. If you find one hooked to your system, cut it lose, and throw it in the trash.
 
I replaced all filters, the one at the primer pump, the water separator, (looks like an oil filter) I put in a new high pressure pump (came with new filter) and rebuilt the low lift pump. Pulled the sending unit and checked/cleaned the screen at the bottom and checked the tank for sediment. Cut the anti syphon valve out and inspected all the gas lines for cracks/air leaks. I searched the entire helm and there is no throttle guardian that I can see. I'm under the impression it looks a bit like the TPS and the rev limiter. (Piggybacked on top of the motor) I'm at a loss with this boat......
 
Also I ran fuel pressure test from the shrader valve and its 36 while running/ moving all the way through the throttle range and holds when shut down for several minutes...
 
Hum....


I guess I would get a few in-line tester, and run the engine with them on, and watch for spark when the engine doesn't want to run.

Are we sure the buzzer is working? (there's 2) I'm wondering if the engine is over heating.
 
After a 30 min run at about 35mph It only took about 10 min and I was able to squeeze in next to the motor and change out the coils so I don't think it's over heating. I was really surprised that it wasn't hotter. Could the temp sensor near the ECM be bad and causing issues??
 
Most of the senders on that engine just act as fuel trimmers.... so they shouldn't effect fueling at higher throttle levels.

Well... if you have fuel pressure... it has to be an ignition issue.

Did you look for a "Throttle Guardian" yet?

did you check for spark when then engine wasn't wanting to run? Or did you just swap coils?
 
Looked all around drivers side helm, no throttle guardian. Ran spark testers and loosing spark around 2k rpm's on 2 and 3 so changed coils at 2,3 position and ran great for a couple times out. Couldn't go faster than 35 but no falling on its face. Now it runs smoother, still only get to about 35mph and its quits again. Not nearly as much but two or three times in the first thirty min. Also at higher RPM's. Probably would run ok at slower speeds lower RPM's. I put two more new coils in and moved them around in the remaining 4 cylinders and no change, still quits. It also sounds like it's trying to rev higher at WOT, almost surging, but it's a jet so hard to tell. Warmed up and running hard it seems to improve a little and occasionally will hit 40mph.
My though is trigger, rectifier or regulator?
 
OK...


Without a doubt... it's electrical. Originally, I thought the power was fading. But it's just cutting.


So... I would pull the flywheel, and get a look at everything. Check the stator, and the trigger. AND... look at the wires, and connectors on each.
 
184.jpg
185.jpg
186.jpg
 
Everything looks pretty good, no obvious issues. One stator wire was saturated in oil, but it was spongy not brittle and the continuity is good
191.jpg
 
Surface rust isn't any issue... so no real reason to clean it.


Check the coils in the stator with a meter. Make sure nothing is open... or shorted to the iron laminates. (sometimes they short internally)
 
Stator looks ok, none of the lines from the rectifiers are shorted to ground and there is continuity in the two pairs.
 
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