Dinghy trim problems / motor size issue?

[Sojourner]

Ciao y'all, I have a few stupid questions about my dinghy.... I've been sailing a good while but this is my first owned boat, and so my first own dinghy that came with her, and I was hoping for some general dinghy advice....

The dink is about 3.something meters, on the small side. The engine is a Mercury 15 hp. With that engine we can plane all together (me + 2 small women) but usually 3 larger people won't plane. But no matter what, including by myself, I have to sit so far forward that I hold the tiller with two fingers half the time to keep the nose down, especially when not planing, and the mound of wake behind the engine is huge at nonplaning to the point where I'm afraid water can (and maybe has) splooshed against the housing, esp when slowing down. Is the motor mismatched in size (too heavy) for the boat? Or should I be adjusting the trim to raise the prop some? It also seems to be eating gas pretty fast (but I have little frame of reference....how long should a 15lt gas tank last for a 15hp Merc? Last but not least, last time out, we got sloshed pretty good from the back, to where the engine sound changed briefly, and not much later the idle (which ran perfectly at the lowest setting always before) now threatens to die at idle unless turned up to highest idle, and even then I'm needing to goose the throttle a bit to keep her alive.

Any thoughts on any of these subjects would be most appreciated!

[Sardean]

Originally Posted by Sojourner

Ciao y'all, I have a few stupid questions about my dinghy.... I've been sailing a good while but this is my first owned boat, and so my first own dinghy that came with her, and I was hoping for some general dinghy advice....

The dink is about 3.something meters, on the small side. The engine is a Mercury 15 hp. With that engine we can plane all together (me + 2 small women) but usually 3 larger people won't plane. But no matter what, including by myself, I have to sit so far forward that I hold the tiller with two fingers half the time to keep the nose down, especially when not planing, and the mound of wake behind the engine is huge at nonplaning to the point where I'm afraid water can (and maybe has) splooshed against the housing, esp when slowing down. Is the motor mismatched in size (too heavy) for the boat? Or should I be adjusting the trim to raise the prop some? It also seems to be eating gas pretty fast (but I have little frame of reference....how long should a 15lt gas tank last for a 15hp Merc? Last but not least, last time out, we got sloshed pretty good from the back, to where the engine sound changed briefly, and not much later the idle (which ran perfectly at the lowest setting always before) now threatens to die at idle unless turned up to highest idle, and even then I'm needing to goose the throttle a bit to keep her alive.

Any thoughts on any of these subjects would be most appreciated!

I have a 15hp mercury on my 10ft polycraft. It is very sensitive to trim adjustment. Adjust your trim so motor is down as far as it goes. Be aware that if that adjustment puts nose down to far boat may be unstable when on the plane, if so bring it up one notch untill its right. I sometimes adjust mine to suit rough conditions, bow down when punching into waves. Bow up for following sea.

[HopCar]

This is a very common problem. The easiest solution is trim tabs. Fixed tabs or spring loaded tabs are fine. They don’t need to be hydraulic or electric. You just need to get some planing surface aft of the transom to lift the stern.

Fins attached to the engine will work as well but trim tabs will add less drag.