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Dominick
Dominick, Marine Mechanic
Category: Boat
Satisfied Customers: 1009
Experience:  25 Years Experience as Mechanic, 20 Yrs Boat Yard Owner/Mechanic, Factory Certified
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Can't get the RPMs and power back past 60%. Pulled the

Customer Question

Can't get the RPMs and power back past 60%. Pulled the bottom plug wire, no difference. Changed the coil and it got a little better, now up to 70%. 3/4 throttle to wide open there is no rpm climb.
Plugs gaped at .98 mm.
Checked bottom spark, it's there, but seemed weak visually.
What am I missing to get back to 100% rpm?
Submitted: 9 months ago.
Category: Boat
Expert:  Jason replied 9 months ago.

Hi Garry, my name is Jason.

Steps 1 and 2 are to check engine compression. And then check spark output by hooking up a timing light to each plug wire one at a time and seeing if there is spark to it or not. Is that something you are able to do?

Customer: replied 9 months ago.
Did that, it was almost like new on all the cylinders.
Expert:  Jason replied 9 months ago.

What does like new mean, what kind of numbers?

Customer: replied 9 months ago.
Sorry phone,
I seem to remember high 90's It was last year and I'm not sure of the gauge.
It ran like lightning, then the following week went to use it and no power. Realized there was no difference with the bottom plug wire off, so I changed the coil and wire. It got better, but not by much.
Customer: replied 9 months ago.
Its a smooth running 70% RPM though.
Expert:  Jason replied 9 months ago.

Is a timing light showing a flash that is consistent with engine rpms on all cylinders?

Customer: replied 9 months ago.
I wouldn't know that. I'm not a mechanic and I don't have the tools.
Expert:  Jason replied 9 months ago.

Earlier I wrote

Steps 1 and 2 are to check engine compression. And then check spark output by hooking up a timing light to each plug wire one at a time and seeing if there is spark to it or not. Is that something you are able to do?

Your reply was "Did that"

So did you do it or did you not do it?

Customer: replied 9 months ago.
I did the compression check, but no electric testing. It was simple trial and error that I realized it ran the same with out the bottom plug wire on. Plus it didn't shock the daylights out of you when you grabbed it while running like the top one did.
Expert:  Jason replied 9 months ago.

And you changed the coil, and still are not getting shocked, correct?

Customer: replied 9 months ago.
Honestly I avoided the coil/plug wires after that. I didn't try at all.
When I looked for spark with it grounded against an engine bolt it seemed weak, but I wasn't holding on to it.
Customer: replied 9 months ago.
I didn't check the other sparks either. It was approaching 100 and I was in the sun. I just put the cover on and quit.
Expert:  Jason replied 9 months ago.

Okay, what kind of questions did you have for me?

Customer: replied 9 months ago.
Besides what to do next ?
Nothing else, I have to leave for a meeting.

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