i've got a merc 140 that when it shifts into gear the boat starts moving at idle speed but when i give it gas only the rpms go up. any suggestions on what it could be?
The first guess would be a slipping prop hub. Paint some fingernail polish across the prop and hub. Run the boat, then look to see of the line still matches, if it doesn't, your hub is slipping. If the line still matches up, then you might have a drive problem or a fried engine coupler.
good advice/<br />If it's the engine coupler, your engine should overheat if you run it very long. That's because the coupler is between the engine & the impeller pump in the drive, so the impeller won't be turning.<br />Check the prop first!