[jbooch]

I'm looking at buying a used 1990 Yamaha boat motor for my 15' runabout. The dealer indicated that it was coming off of a pontoon boat. The price seems pretty reasonable; however, I'm concerned about the stress that a pontoon boat could put on a motor. Especially, if the pontoon boat was large and the motor ran hard for years.Is this something to be concerned about? The dealer had offered to run the motor for me and check the compression in each of the cylinders. If the compression checks out, would there still be a concern of past stress on this motor pushing a large pontoon boat?

[JB]

Hi, JBooch.Welcome to iboats. I would only be concerned about the usual. . . compression, under-load demo, condition of gearcase oil.I would also be concerned about repropping it to suit the new boat.Good luck.

[jbooch]

Thanks JB. I just got my first boat this year and I'm learning an awful lot. What's under-load demo? The gearcase oil is in the lower unit?

[JB]

Sorry, JB, I should have been more specific.Have a compression test done on the engine. All cylinders should compress within 15% of each other, and over 90psi.An underload demo is a demonstration of engine performance under load, preferably on the boat. It should start and idle smoothly, accellerate well and reach the engine's operating range without hesitation or stumble.On the lower unit there are two screw slotted plugs: Drain and Vent. Unscrew the drain (lower)plug and let a bit of the oil drain onto your finger. It should be dark, not milky, and it should contain no metal filings. There should be no water.The correct prop for operating your 15' boat will have a higher pitch than a correct prop for running a pontoon. If you can tell us more about the engine, we can suggest a starting point for prop selection.Good luck.

[BillP]

If the motor came off a small skiff, bass, center console or ski boat I'd be concerned...but not on a pontoon boat. Those folks are laid back and don't beat their rigs up. At least that's how it is around my neck o the woods.