How to increase speed without a new motor

[fubar861967]

My girlfriend and I have a 2008 Sunchaser 20 ft. 8ft.wide has a Mercury 50hp Classic with a 10 3/4 x 12 RH prop and would like a little more speed. We are both new to boating so any advice would be appreciated. We live on a large lake relatively calm most of the time, but it also only averages 12-15 ft. deep

 

[steelespike]

Re: How to increase speed without a new motor

If you can give us your present max rpm and speed preferably by gps that would be a good start.Can't really help much without a starting point.

 

[fubar861967]

Re: How to increase speed without a new motor

The rpm is approximately 5500 speed is 14-15 by speedo sorry no gps

 

[mthieme]

Re: How to increase speed without a new motor

That's not bad and probably the best you're get out of 50 HP on that 'toon.

 

[Silvertip]

Re: How to increase speed without a new motor

You can increase speed by leaving your girl friend at home. But since that's probably not the solution you were looking for, lets look at some facts. First, you apparently have a standard Mercury (not a BigFoot motor) so you are saddled with a marginal setup to begin with. BigFoot motors are made specifically for work boats and pontoons. They have 2.3:1 gear ratio whereas the standard motor has 1.83:1. The advantage of the BigFoot is that it can spin a much larger prop (14 inch diameter) with more blade area. Mercury also makes a good four blade, elephant ear pontoon prop (about a 9P for that engine). The prop you have needs to be small because of the lower ratio gear set. You simply get more "push" with the BigFoot. Since you don't have a BigFoot motor you are sort of stuck with what you have but only a few test runs at wide open throttle will tell you if your combination is optimized. It is recommended that your engine run at 5500 RPM at wide open throttle with an average load. Speed will be whatever that prop delivers. There simply is no free lunch when it comes to props.

 

[coolguy147]

Re: How to increase speed without a new motor

wax the toons and gearcase of motor

 

[fubar861967]

Re: How to increase speed without a new motor

I wonder why the marina we bought the boat from new would package this motor and pontoon together

 

[5150abf]

Re: How to increase speed without a new motor

A pontoon hull is very ineffeciant as it plows through the water rather than riding on the water like a mono hull boat.

The trade off is you lose speed but the ride is much better than a mono hull as you are going thru waves rather than over them.

To get a toon to go fast you need ALOT of power, I have run a 22' boat with a Yamaha V-Max 250 and it would only run @35 so you are kinda stuck where you are, make sure you have the right prop as stated above and that is all you can do.

They probably picked that package because of a price point, they feel they can sell the boat at X price and that is the motor that got them there.

 

[mthieme]

Re: How to increase speed without a new motor

wax the toons and gearcase of motor

LOL.
BTW, wax is counter productive.
Silicone is the ticket - I do the hydro with this.
If you really wanna get serious, there are treatments that mimic sharkskin.

 

[Silvertip]

Re: How to increase speed without a new motor

A BigFoot motor is more expensive than the standard motor. The gearcase is the same as the one used on 75 and 90 HP motors and uses the same range of props which are in the 13-1/4 - 14 inch range - much larger than the little guy on your current motor.

 

[fubar861967]

Re: How to increase speed without a new motor

I'm going to see what they'll give for a trade-in to upgrade the motor the info says I can go up to 90hp but may check on the bigfoot 50hp. Do they have a bigfoot 75hp

 

[mthieme]

Re: How to increase speed without a new motor

I believe 60 HP is the biggest Big Foot.

 

[Silvertip]

Re: How to increase speed without a new motor

75 and 90 HP two stroke Mercs already have a "BigFoot lower unit only they don't call it that because that setup is standard.. That's what the 40/50/60 BigFoot motor is --- 40/50/60 HP powerhead on a 75/90 lower unit.

 

[papasage]

Re: How to increase speed without a new motor

i have a 20 ft. pontoon it has a 40 hp tohatsue 4 blade prop . 11 pitch i think . nothing on the prop but that is what is recommended . it runs about 16 by gps .that is with my wife and me on it it only has a bench on the back of the boat . add 2 adults and 3 kids and slows it to about 8 or 10 mph . check prop and go to less pitch and 4 blades.just don`t git to higher rps than the specks .probably 5500. to mabut 6000 RPM`s
i tried a 19 pitch SS prop 3 blade . i could walk faster than it would go .

 

[steelespike]

Re: How to increase speed without a new motor

Couple of things keep in mind a 50 will use about 5 gallons per hour (gph)at wide open throttle (wot) a 90 will use about 9 gph. My guess is you couild probably get close to 18 or 20 mph.with careful trim adjustment. and prop selection there are 4 blade props intended for heavy hard to push boats.
Carefull weight placement is important as well
If you can get 18 with your 50 a 90 would probably only get you about
25.at a tremendous investment in fuel.One advantage with thec larger motor is you could cruise at the 50s speed and only use about the same fuel as the 50 while your motor loafs along.

 

[fubar861967]

Re: How to increase speed without a new motor

Well checked on trading in the 50hp for a 75hp and they want $5100 with the trade in. I asked if they sell factory reman. and they said yeah but they said they'd have to check and get back to me.

 

[Silvertip]

Re: How to increase speed without a new motor

I did a quick check of one on-line supplier and a 90 HP Merc (carbed two-stroke is listed at 5500) and a 60 HP four stroke Suzuki is $5000. In both cases you get to keep your engine. Sell it and that money goes to the new engine. This is a buyers market. Use it to your advantage. Right here on iBoats you can buy a 75 HP Merc four stroke for $3800. Isn't new, but at an attractive price. Here's the link and from there you can look at their other offerings.

http://www.boatmotors.com/motorparts/index.cgi?pid=7374&flag=2

 

[Rapprunner]

Re: How to increase speed without a new motor

I have a 20' toon that came with a 50 hp Merc---hated it! Traded it for a 90 hp Merc---love it!

Went from 15-17 mph w/the 50 to 22-23 mph w/the 90. Speeds are with GPS.

This is with only me on the boat and ~20 gallons of fuel---of course it slows down when I get 6 or 8 folks on there!

 

[TheDude]

Re: How to increase speed without a new motor

I believe 60 HP is the biggest Big Foot.

I have a 115 Merc 4 stroke bigfoot so 60 isn't the biggest Big Foot..