Repowered 17 Dauntless - performance?

[YoungTurk]

Hello all. I just re-powered my 1997 Dauntless 17', replacing the original Yamaha 130 Saltwater Series 2 stroke with a 90 hp Suzuki. The two motors are almost identical in weight. Anyway, with the current prop the performance is as follows:

4000 rpm - 17 knots
4500 rpm - 20 knots
5000 rpm - 24 knots
WOT is 5700 rpm and 29 knots.

WOT range is specified at 5300-6300.

I'm considering getting a higher pitched prop to get a little more speed but the dealer advised against it as the 5700 WOT suggests that a higher pitched prop might be labored under load. The Dauntless is rated for 90-130 hp so this might be what is expected at the low end of the hp rating?

Otherwise the Suzuki is running beautifully at about 13 hours now. Maybe she'll gain a knot or two when she's fully broken in?

And the fuel mileage is spectacular - literally more than doubled over the old 130 2 stroke!

Thanks for any advice.

Bob

[Phil T]

Bob -

To offer advice, we need some detailed information.

Please detail what the current prop is; make, model and size.
At what height is the engine mounted.
What is the passenger and gear load when performance was tested.

I would say you are under propped and should shoot for WOT rpm's of 6-6100 and select a stainless steel prop. Recommendation once details above provided.

[YoungTurk]

Hi Phil.

The current prop is a Suzuki (I assume?) 3 x 13&3/4 x 19 aluminum. It is also offered in 17, 21 and 23 inch pitch.

Hmm not sure about the mounting height - I can find out.

Load was two adult males (about 400 lbs) / full tank of gas @ 39 gallons (240 lbs or so?) / and a full 13 gallon bait tank (another 108 lbs or so) located on top of the aft port jump-seat. The hull is 1500 lbs and the Suzuki weighs in at 348 lbs (25 inch shaft).

Hmm that's pushing 2600+ lbs ...

Anyway, I appreciate your input Phil thanks,

Bob