[flipjoe]

getting ready to switch out the 40hp on my pontoon with a 90hp v-4 what should i except for speed it is going on a 20ft harris floteboat sunliner, i usally get about 15-17mph out of the 40hp,a 90hp is what my boat is rated for anybody else running a 90hp?
thanks

[DMAN1968]

I would think you should be able to get to 27 mph, maybe a little more. It all depends on the weight of the boat, the prop you use, underskinning or not, clean toons, etc...Well, depends on a lot.

Suffice it to say that you will like the change. The best part is that you will be able to cruise at 1/2-3/4 throttle at the speed that used to be your maximum.

Is the 90 hp a new motor?

[rickdb1boat]

20'er with a 90 Merc. 4 stroke. Only myself onboard...

[tashasdaddy]

proper propping and height of that motors is what is going to make the biggest difference.

[steelespike]

As suggested 27 or so mph.Keep in mind you'll be using about 9 Gallons par hour(gph) at wot.(wide open throttle)instead of the 4 gph of your 40.
Of course you can throttle back to save gas and your 90 will be loafing instead of running its guts out like the 40.Be sure to get it propped right.

[flipjoe]

thanks for the replies, i will defintely prop it out right, it is a two stroke, i am going to try to get it around 5500-6000 rpms.

[sc_shane]

I have a 25' Crest Savanna model - big heavy girl. I typically top out in the low 20s, but with no one but me on it, less than half a tank of gas and virtually no gear, I can make her go 26 or 27. Just make sure you prop it right so you can get the correct RPMs at WOT. Took me 2 tries to get mine dialed in, but she's great now, even with 12 people on her!

[colofiremedic]

I have a 24 foot pontoon with an 88 Johnson. I get about 29mph GPS at 4500 feet with a 15 P prop. The 88 Johnson is actually a 90 HP non-oil injected motor. That might give you an idea of potential.

Happy Boating!!!

[littlefuzz]

23' Riviera Cruiser with a 85hp johnson , 21mph is all I can get.