Approximate speed ??

[brfrsc]

Okay So I've jumped into getting a boat to drag the kids around the lake. Go to get insurance and the wanted to know the top speed. It's a 16' tri-hull with a 90 hp outboard. Anybody got a realistic idea of the top speed ?<br /><br />Thanks, Bruce

 

[CaptainPuget]

Re: Approximate speed ??

Roughly: 200 times the squareroot of the power to weight ratio. i.e. 200*(hp/lbs)^1/2

 

[Dhadley]

Re: Approximate speed ??

Or use the propeller pitch and gear ratio to find theoretical speed and estimate 15% slip. <br /><br />A 17" prop will probably allow the motor to turn 6000. With 15% slip you are just under 42 mph.<br /><br />You may have a touch more slip but that should be close.<br /><br />Good luck!

 

[Jack Shellac]

Re: Approximate speed ??

Using JB's formula, which came out very close on my boat and guessing the weight of your boat at 1100 lbs, I come up with 43 MPH.

 

[Snailman]

Re: Approximate speed ??

Oh for God's sake! Just get a little hand-held GPS unit (a buddy of yours has one if you don't) and get a reading from that!

 

[CaptainPuget]

Re: Approximate speed ??

Since it's for the insurance company, I'd guess the top speed to be about 20 mph.

 

[FlyBoyMark]

Re: Approximate speed ??

Speed should be closer to 50 MPH....49 MPH @ 1500 lbs. Question is, what does the boat and motor weigh plus people and gear? @ 1800 lbs., it is 42 MPH. Keep in mind these figures are with different props optimized for the load as per Mercury computer.....