Doel fin on a 9.9 hp on an inflatable

[Points]

Guys,
I have a 9.9 Yamaha (1993) on an Avon inflatable. Does about 18.5 mph with me and the dog ~260 lbs (dog =30+); nearing hull speed; 17 mph with the wife who is + 110 heavier [than the dog, not 260].

Motor is a 4 stroke- like 100 lbs. Thought about messing with the prop but there are not a lot of options- most are oem spec’d. Wanted the boat to pane faster w/o a sacrifice of top speed. Right now wife and I can sit side by side in the rear with me at the tiller while on plane, but a no wake zone, she has to go up front to get back on plane. Even solo with the dog the boat doesn’t pop up that fast.

So I read some reviews, bought the doel fins, maybe some last words before I drill.

Advice recommendations, experience?

Doel fins:
http://www.davisnet.com/marine/products/list_marine.asp?grp=m18-2

sorta like the boat but 13 years older:
http://www.boat-finder.net/1380/details.php

[GREENFEATHER]

I used them on my boat and they did a hell of a job. I had a 22 foot Renken centre console with a Johnson 175 on it.

[Points]

any noticable power, speed loss? Install tips?


(I know we're at different applications but I appreciate the replies.)

[GREENFEATHER]

It got up on plane a hell of a lot faster. I didn't notice any loss in speed.

[JimmyC]

I had a set on an old 11' Boston Whaler with a 20hp Johnson. They helped bring the boat on plane a little quicker and easier. I didn't notice any loss in any areas at all.

[Points]

I was a bit apprehensive about drilling holes in the anti-cavitation plate; but I mounted them up; tested them; can almost plane with both of us in the stern seat- it was never even close before. Also planes at lower speeds and lower throttle. Before I had to throttle up to get on plane and then back down.

Does 17.5 with the wife. I was worried about WOT speed decrease.. I think it may have increased (suprised) but to truly tell I need to test with the dog. I have better data with her. Making the motor a little bit more unwieldy is the only drawback so far. No fuel economy data but there has to be at least a minor increase given the benefit to plane speeds/ease.