What size 4 cycle outboard do I need?

[Polecat]

To push a 7000 lb Pearson Renegade, at hull speed of 6.4 knots against a 10 to 15 mph wind in mild chop? I'm looking for the minimum size to get this done.
jim

[Oscar]

Well, if it's linear, which it probably is not........my 26000 pound Catalina did fine on 44 horses...... So my guess is that a 15 horse Honda or similar, with the proper length shaft and the proper prop er, would do fine. I have no scientific data to back that up. Just an educated guess. The 9.9 would be a little small. (Had that on my 250, 4500 lbs where it was more than adequate.) FWIW the 9.9 and the 15 are the same engine, the former being de-tuned to meet the 9.9 max there is on many inland waters.) Once again though, sticking out the back you are going to have a cavitation problem unless you mount it low and get the XXL shaft.

[Hirilondë]

Hull speed for a Renegade is 6.14. At 7000 lbs the idea engine would be at least 15 hp, if not more. I find a 9.9 4 stroke Honda does almost all I could ask of it, in strong winds and seas I can make 5 kts at 2/3 throttle, barely more at full throttle.

[forrest]

With 10-15 and a mild chop you sail! ;)

I have an 8hp Honda on my Renegade, it cruises around 5 knots.

My guess is that you would need a prohibitively large outboard to go hull speed into 10-15.

[Polecat]

Thanks for the response guys - Settled on an elec start 9.8 Tohatsu. Tohatsu's best calculation or best guess was somewhere between 18 and 21 hp...... The reason for wanting good speed is the long long inland waterway run. Hoping to cut south offshore from Pensacola weather permitting.
It should be here this Friday -- hmmm now to find a tree tall enough to lower the Tohatsu into the stern locker.
Jims shade tree boat service - will take pictures

[DaleH]

Get the largest 'elephant eared sized' low pitch prop you can. You want a PUSHER prop on any kicker, otherwise you'll be lugging the motor.

[Polecat]

Here is what is available - I was going to wait & see what RPM I get once it's in the water. Their suggestion is to check the rpm WOT and go down 1" pitch for each 200 rpm that you are below 5500 rpm. The reason I picked the Tohatsu engine is that it seemed to have a good selection of props.

MFS8 & MFS9.8
(4-Stroke) Light 8.5 9.5 3 3B2W645191
8.5 9 3 3B2W645171
Moderate 8.5 8 3 3B2W645150
8.9 7 3 3B2W645140
Heavy 8.7 7 4 3B2W645120
8.5 6.5 3 3B2B645131
8 6 3 3B2W645126
8 5 3 3B2W645125
8.7 5 4 3B2W645110
jim