Should I double the size of my motor?

[keninaz]

I have a Lowe 1467 WT boat. I bought it with a 9.9 Mercury manual start 4 stroke motor. I had to change the prop to a 6.5" to get any speed/plane ability as I use the boat quite a bit at altitude. It now does about 14 MPH loaded with gear for fishing at the proper RPM at 5000'.
I have been looking hard at the electric start motor in the 20 HP range. I think that this would almost double my speed and the motor weighs about the same as my 9.9. I read a test with that motor on a similar hull/weight and it did 27.5 MPH but I think the overall load was lighter. I know the elevation was lower.
It would certainly be nice to have the speed and the electric start. I don't thing the MPG would drop all that much. I don't need top speed so much as out of the hole torque but 20 MPH would be very nice.
Anyone think this is a good idea or just a waste of money??

 

[jbcurt00]

If you are running WOT all the time now, by swapping to the 20hp you'll cruise on plane below WOT, may use less.gas.... may... if you cant stay outta the throttle, you'll use twice the fuel at WOT...

If you can afford the new 20hp, the boat is rated for it. Unless you fish a lot of hp restricted lakes, I dont see any reason not to jump up to the 20...

Cant remember anyone I know saying the wish they had less hp on tap...

 

[keninaz]

The boat is easily rated for the power. I bought the lower HP motor to fish some lakes locally that only allow 10 HP or electric but I find I don't fish them all that often and I could just use the electric trolling motor for those.
I know I will lose money on the swap but I was thinking that not having to run WOT to get about 14 MPH at best would be better.

 

[alldodge]

Get the bigger motor you will love get up on plane and not taking all day to get where you want to go.

 

[NYBo]

Double the HP does not equate to double the speed if both motors get you on plane. I don't remember the formula, but you may get 50% more speed if propped right.

 

[steelespike]

Definitely go for the 20. the 9.9 is about 84 lbs, the 20 is 115. A broad guess if you can get 6000 out of a 9" prop maybe you could make about 20.
6000 out of an 8" = about 18.

 

[metriccrescentwrench]

Double the HP does not equate to double the speed if both motors get you on plane. I don't remember the formula, but you may get 50% more speed if propped right.

Probably closer to about 35% more speed when doubling the power (don't have a calculator in front of me to do the math right now, but I'm sure I'm in the ballpark).

I'd definitely go for the extra power, underpowered boats aren't much fun.