Re: Motor revving
Your post is a little confusing--The engine speeds up while slowing down. Do you mean the engine will rev-up while the boat itself will slow some? If so, then there are two places to look at firsT.
1. Check the prop to see if the rubber hub is going bad and spinning insude the prop hub. This is easy. Take off the prop, and mark the bronze hub in the back of it and also mark the prop aluminum hub in a corresponding spot. After the engine revs up, check to see if the marks have moved. If they have, then either have the prop re-hubbed or buy another one.
2. Check the height of the cavitation plate. It should be even with the bottom of the hull or very slightly above it (1 inch or less). If the engine is sitting too high on the transom the prop will occasionally suck air, ventilating and losing thrust. Engine will speed up while boat goes slower. Tilting the engine too far out with the tilt pin could also cause this problem
Now, If it revs up then slows and quits running, this sounds like a fuel delivery problem. When a carb starts to run out of fuel, it goes lean and the engine will speed up some, then as fuel runs too low it will slow and die. When you go to restart it, the pump will supply enough fuel until you go to full throttle then sooner or later it will repeat.
You need to check the whole fuel system from tank to carbs to be sure that fuel is being maintained at the correct level in the carb at all times. (It could be something as simple as a partial clog in the tank strainer or quick connect fitting. It could also be a bad pump diaphragm or sticking carb float.) This could also cause spitting and rough running at idle as would too low an idle speed. So, first check fuel, then be sure idle is not too low. Those little engines usually don't have tachs, but idle speed should be the same as the bigger ones:700-750 RPM
And don't forget, if you manage to grab some weeds, the prop will lose thrust until it clears them
