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Ask Dominick Your Own Question
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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2004 M40D2 Tiller control, on 15' hobie power skiff, manual

Customer Question

2004 M40D2 Tiller control, on 15' hobie power skiff, manual tiltThe boat will not reach wot and speed that it should. I had it running about 30 mph for about three trips, and this was just last year after I put new throttle cables one it as one had broken. It generally runs at around 20mph +/- 1mph. When it was running 30mph, it sounded like it was running at higher rpm than it ever does. When I twist the throttle to wot while watching the linkage, the carb linkages are maxed out. I just rebuilt all three carbs, (yesterday), and the fuel pump, and replaced all fuel lines from remote tank, as well as inside cowling. I put an inline spark tester on each plug, (seperately), and all three had a strong looking spark.Water tested it today, and the carb job and fuel pump made a huge difference in how smooth she is running, but still seems to max out at an rpm lower than wot. checked linkage on throttle, it is maxing out. Stumped, other than thinking that it could be timing related or internals worn?
Submitted: 1 year ago.
Category: Boat
Expert:  Charles replied 1 year ago.

Hello, my name is***** will assist you.

Expert:  Charles replied 1 year ago.

How old is your fuel?

Have you done a compression test yet?

Customer: replied 1 year ago.
Brand new fuel, have not done a compression test yet.
Customer: replied 1 year ago.
I know for a fact that it is not reaching WOT, and looking for a cause other than all the work I have done recently to it. I did not look into synchronizing the carbs with the timing, although I don't feel like that would do this. It is running so smoothly as of today after I put the carbs back on etc, etc... Just feels like it is not able to hit this "powerband" that it would hit intermittently
Expert:  Charles replied 1 year ago.

if the engine is down on compression, or a cylinder is losing spark, either one will cause this. That is why a compression test is so important.

Customer: replied 1 year ago.
I guess I'll have to get back to you as soon as I can check the compression, and I already checked for spark with an inline tester. I understand that the inline tester is not going to reveal a weaker spark in one necessarily, but they all lit up pretty strong. Is there anything else that would prevent it from reaching wot in the timing? I would think that shot rings in a cylinder would present a fouled out, or burnt spark plug? If you want to wait until I can check the compression, I'll do that as soon as I can but it may not be until tomorrow.
Expert:  Charles replied 1 year ago.

There are no time limits here. Simply reply as you have been doing today, and I will receive it.

Customer: replied 1 year ago.
Great- thanks and have a good evening!
Expert:  Charles replied 1 year ago.

You too.