zodiac wont plane properly

I have a 12.5ft old zodiac soft bottom with inflatable keel. It has a 15hp short shaft.
Problem is, I cant get the bow up and out of the water when I plane off. It seems like the bow is being forced down witch causes terrible handling and a very wet ride.
I've tried adjusting the angle of the L/U to get the prop to push the stern down. Tried every setting. When I bring the prop out away from the transome, it cavatate's.
The trim tab plate of the outboard is about 1.5 inches below the bottom of the boat, which sounds O.k..
Does this problem sound like something a longshaft motor would fix?
P.S. The boat was empty, with just me in it while testing.

Re: zodiac wont plane properly

Underinflation.

Re: zodiac wont plane properly

If your tansom height (bottom to engine mount) is 40 cm or slightly less, is for short shaft motors. Try sitting inside floor in middle sib towards bow with arm extended, place trim angle at 2-3 hole from transom, check tubes and keel pressures (3-3.5psi) re inflate if needed. Full wot and see what happens.

Happy Boating

Re: zodiac wont plane properly

I had the same issue with my 13'9" Mark II Grand Raid. I found 4 things helped. Besides the advise already listed this is what I found.

1. Dolphin fin is a must. Some prefer trim tabs but the fin works well for me. It seems counter intuitive as this forces the bow down but it really works on my boat. Eliminated the cavitation issue and pops the boat right up on plane. It does cut your top end speed by a MPH or 2 but the difference in acceleration and stability is worth it. Besides over 20MPH who cares about another MPH or 2.

2. Weight distribution is key. This weekend I tried out my new bench seat/locker/rod holder combo and where it was placed in the boat made all the difference. 6" too far back = poor plane and soaked; boat was a total dog. We played until we found the sweet spot and boat was back to a scary fast swell bashing beast. Seriously 6" of weight placement made all the difference in the world. By yourself this is even more important. Put your gas tank in the bow along with the rest of the gear to level out the load.

3. More HP!! I had a 15HP and have upgraded to a new 25HP Yamaha 2 stroke. The 15 would get on plane but with a load sometimes had issues getting to the sweet spot in chop quickly. The extra 10 ponies really helps power through rougher water to plane. This is the most expensive solution but it is nice to have extra power. The 25 still has a dolphin fin like my old 25.

4. Still, I have come to think the extreme light weight of these boats makes them have issues getting the trim perfect and extra passengers or gear can make you have to re-adjust. I am looking on how to add electric trim to my OB without adding a ton of weight as the 25 OB is already on the threshold of being too heavy to lift on and off by myself. Being able to adjust trim underway would be a very nice feature.

Now if I can only figure out how to stay dry!! Boat has no leaks but I still get a ton of water on the floor by the end of the day.

FYI, wind picked up Saturday while crabbing. After a while it was only 20'+ boats, another inflatable and myself on the water. While I am 6' less in length we were still more stable than the $30K boats around me. (and as fast!) God these things are cool!

edit: Oh yeah! SHORT SHAFT IS A MUST!!