50 hp vs. 90 hp and resulting speed

[JonathanEngr]

I have a 24' pontoon with a 50 hp Mercury, and it has a top speed of 16 mph (determined by a Tom-Tom GPS unit). The speed of the boat is perfect for me right now, but I'm curious about possibly upgrading the HP down the road. First of all, how do you determine the max HP allowed for this boat? The only thing I've seen that might hint to it is the capacity sticker that reads "Capacity 12 persons or 1800 pounds, 2200 pounds with a 90 hp engine". Does this mean 90 hp is the max?

If I did upgrade to a 90 hp motor, what differences could I expect besides a capacity of 400 more pounds? Would the speed increase be significant? It seems pontoons are destined to be somewhat slow. I was looking at a new Starcraft tri-poon at a marina the other day, coupled with a 150 hp engine. The salesman said the top speed was 35 mph. Thus, is it likely that I would even hit 20 mph with a 90 hp engine? (I'm assuming that an 80% increase in HP DOES NOT equate to an 80% increase in speed).

Instead of sinking $5000+ for a new engine in the pontoon, would I just be better off to find a used ski boat for around that same price if I want to pull a skier or scare the heck out of someone on a pull-behind float?

 

[wing dam]

Re: 50 hp vs. 90 hp and resulting speed

I have a 90 yamaha 4 stroke on a 2386 and run aroung 22 for a top speed but it does not fall off much with a load.
With 1250lbs and a tube with another 225lbs on it I still hit around 20mph.

 

[Mike722]

Re: 50 hp vs. 90 hp and resulting speed

You might double check the plate, but I think it might mean 12 people or 1800 lbs of people or a total of 2200 lbs people and gear. HP of engine should not determine capacity. 90 would be the maxium.

 

[onthelaketwo]

Re: 50 hp vs. 90 hp and resulting speed

I have a 24' manitou with two tubes. I get 22 MPH @ WOT of 5000 RPM with a 90HP evinruide etec.

In theory I could get a little more with a new prop by running at 5000 RPM.

Hope that helps

 

[Rancherlee]

Re: 50 hp vs. 90 hp and resulting speed

I'd say 22-24mph would be about right with a light load. I did the 40 to 70hp jump on my 20' and went from 17mph to 23mph top speed. The BIG difference is the 40hp would drop to 11mph with 6 people,the 70 will still do 20mph with 6 people on board and the engine turning 5800rpm. I only gained 6mph empty BUT Loaded I have a 9mph difference.

 

[rogerwa]

Re: 50 hp vs. 90 hp and resulting speed

I have a 25' that I upgraded from a 40 to a 90. The WOT is about the same for me as well. One of the benefits is that you get a faster cruising speed without your engine working as hard. Which means a more pleasant trip without the screaming motor behind you.

If water sports is your goal, pick up a Jet ski that you can tow behind you and then use that for tubing or skiing, with your Toon as a base station on the water. THat would be the best of both worlds..

 

[JonathanEngr]

Re: 50 hp vs. 90 hp and resulting speed

Thanks for everyone's replies. Two questions:

1) What does "WOT" mean?

2) The boar I purchased was used regularly, but docked in a marina when not in use. It has tons of dirt/scum/scaling on the pontoons, and someone told me the other day that it would make quite a difference if I cleaned the pontoons. I'm sure it will make a difference since it will reduce the friction and drag, but how much?

I do have a 3000 psi pressure washer, so I thought I would start with it and remove as much crud as I can. Then I guess I would use a polishing wheel and aluminum polish and try to shine them up. I'm going to make another post about how best to get access to the 'toons to do this job.

 

[JonathanEngr]

Re: 50 hp vs. 90 hp and resulting speed

Ahhhhhh... "WOT" means "Wide open throttle"??

 

[ridefst]

Re: 50 hp vs. 90 hp and resulting speed

Ahhhhhh... "WOT" means "Wide open throttle"??

Ding ding ding - we have a winner!
Yup, you figured it out.

I would definitely vote for blasting with the pressure washer, not sure I'd spend time polishing though (unless you're doing it for looks, would look very nice). I don't think that polish vs dull would make much difference in speed, especially not for the amount of time it would take you.

 

[JonathanEngr]

Re: 50 hp vs. 90 hp and resulting speed

Thanks for all of the terrific replies. This leads to my next question....

Due to the expense (prob $5000+ for a 90 HP 4-stroke in great condition), I'll likely just buy a new boat entirely if I'm looking to get near 40 mph or above (or go with the jet-ski idea!). In the meantime, what is the best way to maximize the performance of my existing pontoon? Obviously, I plan to clean the pontoons (and polish them mainly for looks)... any idea what difference it will make scrubbing off all of the scaly build-up? Aside from that...

I've heard of strakes on the pontoons...? Changing out the prop...? I've heard that it's a good idea to keep a spare prop onboard just in case. I don't know my existing prop size and pitch (I'll look next time I'm at the lake--I assume it's stamped onto the prop?), but will "high performance" props really make a difference? I hear that they can add an inch of prop length based on the way they're designed in calculating theoretical speed, which in my case would add 2-3 mph. What about the bolt-on hydrofoils you can buy to go over the smaller ones mounted on your engine to give you more lift? Etc., etc., etc. I also stumbled across the "pontoon water glide", but after looking into real-life installs in forums, it didn't make much speed difference (and my HP/pontoon length doesn't fit into the recommended category on their site, anyway).

Again--right now I'm thrilled with my boat, and it sounds like jumping to 90 HP wouldn't gain me $5000 worth of speed. I would just like to max out what I've got to get me from point "A" to point "B" as quickly as possible if needed (like when I was caught in a hail storm on the lake the other day--scary!).

 

[JonathanEngr]

Re: 50 hp vs. 90 hp and resulting speed

Any thoughts?

 

[rrhodes]

Re: 50 hp vs. 90 hp and resulting speed

Strakes won't do much for you unless you have about 150hp. At least that is what the manufacturers will tell you. I have seen a few mph 2 or 3 increase with a 115hp and strakes. Changing props on a toon will only net you +or- 1or2mph so you should prop for the correct rpm.

As far as a 40mph toon you are looking at 175hp and up. Most guys I know with 150hp and strakes get about 38mph.

 

[fubar007]

Re: 50 hp vs. 90 hp and resulting speed

Sounds about right 22 to 24 is about what to expect. crest IIi 28 ' 90 Merc. Inline 6. More weight less top speed.

 

[James R]

Re: 50 hp vs. 90 hp and resulting speed

I have picked up on your proposed 'toon cleaning. I had a real dirty toon that appeared to have a mineral deposit, dirty brown in color, six inches or so wide at the waterline. Tried many things including Shiny Side and JJV's best. Nothing would touch it. It laughed at my high pressure washer. Muriatic Acid a cloth and industrial gloves and of course a lot of work and pressure washing to remove the acid residue, did the job. Stay out of the fumes, they will kill you I think.

 

[Volphin]

Re: 50 hp vs. 90 hp and resulting speed

I have picked up on your proposed 'toon cleaning. I had a real dirty toon that appeared to have a mineral deposit, dirty brown in color, six inches or so wide at the waterline. Tried many things including Shiny Side and JJV's best. Nothing would touch it. It laughed at my high pressure washer. Muriatic Acid a cloth and industrial gloves and of course a lot of work and pressure washing to remove the acid residue, did the job. Stay out of the fumes, they will kill you I think.

The fumes are indeed awful and will burn your eyes, nose and lungs. The liquid will burn whatever it touches. Here is how I handle muriatic acid: Full protective gear including Full shield goggles, respirator and thick rubber gloves. Then I connect the jug to a RoundUp pull and spray top. Pull the lever (set to stream) and coat the pontoon. This allows you to be well away from the pontoon and avoid any splash over. Try to be mindful of the wind and stay upwind. Then wait 10 minutes. Do not agitate the deposit. Rinse with water. Repeat as needed. It will melt off those caked on lime and calcium deposits in short order. But your safety comes first. It is powerful stuff.

V

 

[artistwood]

Re: 50 hp vs. 90 hp and resulting speed

Sharkhide pontoon cleaner works great and wont hurt the bunks. Spray it on, hose it off.....youre done! Just stand upwind when spraying cause it will burn your nose but it's safer than the Muriatic Acid.