On Jun 15, 9:44 pm, trainfan1 wrote:
wrote:
On Jun 15, 8:57 pm, wrote:
Hi all,

I have a small (14 ft) wood boat that I built myself. I put a 25 HP
(Suzuki 4 stroke, manual trim) outboard on it. The angle of the
transom is such that the outboard is always trimmed in (even when I
adjust the bracket to the most trimmed out pin). The outboard may also
be a little bit high. The cavitation plate is at an angle in the
water, the front is lower than the back, the front is probably level
with the keel or 1/4" high, while the back is higher than the keel.

What I have noticed in the water is that the boat creates a lot of
spray, a big rooster tail appears behind the boat (maybe 4-6 ft
behind), and the performance seems quite sluggish. I am a little
confused as I expected that a trimmed in motor would not generate a
rooster-tail of water coming up, quite to the contrary that it would
push water down.

Could the trim angle or the motor height be causing this problem?

Thanks
--Hector

One correction to my post, the cavitation plate is at an angle, the
front of the cavitation plate is higher than the back (I wrote the
opposite in my post).

Hi Rob,

Thanks for your reply.


I was about to call you on your contradiction.

You need a transom wedge to correct your geometry problem. What you
really want is the cavitation plate surface parallel to the water, or
slightly the opposite of what you have now. With your negative trim
situation now, the bow of the boat is being forced down & plowing
into/through the water. To get the boat on plane, you need bow lift.

http://www.brokeboats.com/trim.jpg

Your rooster tail is probably spray off the cavitation plate.

This is a very good idea, I will install a wedge and see how the
proper angle improves things.

What is the height of your transom?

Is your Suzuki a 15" shaft model or a 20" shaft model?


The transom was originally 20", I cut it out to around 17" given that
the engine is 15". I feel that I may also need to cut further, but I
may want to first correct the trim before cutting more into the
transom.

--Hector