1989 20 CC Seacraft running flat at top end

[Yknot]

Hi everyone,

Looking for some help. I'm looking at purchasing a 1989 Seacraft with a 225 Yamaha 2 stroke. The boat seems to run flat a t high speeds. I'm not familiar with the haul and not sure if this is normal for this haul and engine. I thought with this size of an engine it would porpoise a lot but it didn't. Any thoughts would be greatly appreciated.

Thanks

[DonV]

Runs flat, no porpoising?? You should be happy!!!

[Yknot]

Originally Posted by DonV

Runs flat, no porpoising?? You should be happy!!!

Thanks, I just wasn't sure how this haul rides.

[Bushwacker]

Originally Posted by Yknot

Hi everyone,

. . . The boat seems to run flat a t high speeds. I'm not familiar with the haul and not sure if this is normal for this haul and engine. I think what you have is a Tracker or SeaCraft industries hull. . .

Not sure about the latter, but the Moesly/Potter hulls had a bit of rocker in the innermost panels and a little bit of wedge in the outer panels to provide stern lift and help it to plane at 12-13 mph with a 300 lb motor. This was a brilliant design, because deep V's develop more lift as speed increases, so the outer panels are clear of the water about 40 mph, thus eliminating the stern lift from the outer panels, and allowing the bow to rise due to the rocker in the inner panels, thus reducing wetted surface and allowing higher speeds. (Notice how running angle increases in attached plot from 0.5 deg at 36 mph to 1.25 deg at 39 mph!)

The tracker hulls are a bit longer, so maybe they eliminated the rocker in the inner panel. I'd recommend checking the inner panel with a long straight edge to see if there is any rocker in it.

[manitunc]

My 1968 19' with 2004 Evinrude 150 DI can hang the bow up if I want with engine trim, or bury the nose with tabs. Running wide open and trimmed up, the spray starts at the stern corners, none out the side, almost like a bass boat. Runs about 45mph at top end.

[tommyg29]

My 89 trims pretty well and runs fairly flat at 5400 rpm and about 45mph. Under ideal conditions and running light (which I havent done yet) it will probably top out high 40s.

[Reelsknotty]

I had a '86 with a 225 Optimax on it and it never porpoised. It didn't have trim tabs either.

[gofastsandman]

Originally Posted by Reelsknotty

I had a '86 with a 225 Optimax on it and it never porpoised. It didn't have trim tabs either.

My 89 did when I first got her.
Had a pos Mich. match prop on the 375 lb 150 rude.
AV plate below the keel.

Jacked her up 1 1/2 inches above the keel and put a mirage + on her and poof.
Happiness.

Prop design characteristics cannot be emphasized strongly enough.
Bass boats use bow lifters.
Our children can`t get enough stern lift.