porpoising

[bostonwhaler]

just upgraded my motor on my little skeeter to a 90 from a 50. the bow bounces like crazy. had to get my wife to sit on the casting deck to get it to plane out. Unless I had it at full throttle the bow would porpoise, and she was reving over 6k. I was gettting 40 mph. My question is I guess will changing my prop from a 17p to a 18-19 p take the bow bounce away? I think my 50 did the same thing untill I put a fin on the motor but cant remember. Any help would be awesome.

[toobinator]

Are you porposing all the time or just when you are trying to get on plane. If it's when you are on plane you might try trimming down a bit. Sounds like some set-up issues. If you are having problems planing out, but the motor is over revving, you might add a weed ring to the prop, or drop the motor 1 hole.

[bostonwhaler]

I checked the boat, I was on the second pin, I took the bar out and am going to try that this weekend. It was porpoising if I wasnt going almost full throttle. I definately need some tuning. Gonna try this weekend.

[Raminator]

Your motor height is way to high, and you are trimmed too high, if you lower the motor, you will be able to control the porpoise,your prop is blowing out at speed as she tries to plane, nothing to do with pitch.

[NMG]

A pin? Don't you have power trim on that setup? If your prop is blowing out you'll hear and feel the revs spin way up as the prop loses grip. Is that happening? Also, what's the max HP rating for the boat? Perhaps the 90 is just too much engine both HP power and weight wise. That could introduce performance issues as well. There are LOTS of variables to consider here.

[bostonwhaler]

every boat still has the pin setup even if you have tilt and trim.

[NMG]

If you have power trim you won't want a pin in there as it will stop your engine from trimming all the way down. Trimmed all the way down is how it should be positioned when you first start up and then once you are on plane you would start trimming up to gain speed, RPM's and to set the best running position for the boat.

If you are having problems getting on plane it could very well be because the engine isn't trimmed down all the way down and the angle of the engine at takeoff is wrong. This could also explain some of the porpoising. On many boats, once you are on plane if you trim up too much you can get the bow bouncing. Mine does it as well. When that happens, you just need to trim down to the point where it stops. That is then the best running position for that given load, water conditions, etc. It's not going to be the same position every time.

Regardless though, to realize the best performance you need to be able have that full range of motion so that you can adjust your engine trim. If you have a pin in there it won't allow it. I've only ever seen a pin on smaller outboards that did not have power trim, usually 25HP and under.

[Lorne Chapman]

Your motor needs to trim down more (tuck under), it's not able to carry the weight of the nose. A cavitation plate whale tail will help significantly.

[bostonwhaler]

I was going to take it out this weekend, but we were having wild winds here in the valley. I am certainly going to take the pin out and realy on the tilt trim, I was for sure not tucked into the boat far enough.

[tinman454]

You should also try and move some of the weight around in the boat to help with this prob.