Need more power.

[Old Screwball]

Re: Need more power.

My 18' Party Barge with a 75hp Merc will go 24.6 mph. Tried 4 props, a 3 blade, aluminum 12 pitch gave me the best RPM and speed. Wanna go faster, take it off that restricted lake and get the biggest motor your transom will stand.

 

[bigpimpin]

Re: Need more power.

Uneless something is REALLY jacked-up, nothing you can do is gonna make any difference. You could toss a zillion bucks in that motor and it won;t matter much. At that power level and at that speed doing things like underskinning would have very poor ROI. Sounds like you have the correct prop...perhaps changing to something that will get you in the 5500 range would help...depending on the max rpm recomendation for that motor. Otherwise, the only good option for speed is changing lakes.

But, I would not be too upsept about your buddy blowing by you with his 25. Arguing over who's 25 hp motor is faster is really sort of a non winning battle. I used to have a motor like this. i am not poking fun at you, rather having empathy.

Thanks, I get it with dumping to much money for not enough reward. Trust me if it wasn't for our 20 closet friends an the permanent set up on the water that we have now I would have a 40' 1000hp jet boat. But for now guess I'll just chill out an poke along the lake Haha. Thanks everyone for the input!

 

[MikDee]

Re: Need more power.

Wait, If your WOT is only 5,000RPM, you're lugging your engine! Not good for an engine! The specs show it should run between 5,000-6,000RPM. You have the wrong prop on there. You didn't state your prop pitch #? But, whatever it is you can drop down to a lower pitch. Usually pitch changes are in 2's, so for example if you have a 12" pitch prop, drop down to a 10" pitch. I'd say drop down to the next lowest pitch, and stick with a 3 blade prop for speed,. You might even be able to drop down 2 steps on the pitch, if you can find someone to let you try out a prop. The trick is to be as close to 6,000RPM when normally loaded, & ready to go. You should definitely see a speed increase with this. Or, get back to us with your prop numbers, so we can advise you even better. good luck, Mike

 

[MaPaHa]

Re: Need more power.

I would get with a good mechanic and see if there's anything that could be done with the engine such as changing the jets, timing etc. I had an old (1970's) Mercury 115 6 cyl on a couple of boats years ago and I messed with the timing just a bit and ran octane boost in the gas and it picked up a little power. I never drilled out the jets on that motor but I have on a Ford 6 cyl truck engine. I would start a new thread on the Mercury outboard page and see if there are any engine mechanics there that might not follow the pontoon page and see what they think about turning up the engine. Just know anything you do will probably be met with some words of caution against blowing up the motor. But it's generally known that the major difference between some models of motors in the same line lies heavily in the carburetors and/or exhaust. I doubt anyone will stop you on the lake and blueprint your engine as long as you don't "advertise" it.

Next I would underskin the boat with the idea that it will help when you have a load on it and/or in rough water. The boat probably rides high enough with a light load in smooth water that water doesn't hit the bottom of the deck much. With the boat running look at the last few feet or the rear over the side and see if any water is coming out over the toons. If so, then underskinning will help. Look out the back and if it looks like a square wall of water that's rubbing the bottom of the floor or you can feel surges when you hit waves then I would underskin it.

Then... after you've made all the changes to the motor you're going to make... and you've made all the changes to the boat you're going to make, I would buy a performance prop. I've used "Power Tech" props and had very good luck with them. They will help you select the right prop for what you want and then you can order it through one of their dealers. If you want to go fast with a load you could ask them about a 4 blade prop for that motor otherwise, they may recommend a 3 blade of some style. Props make a HUGE difference in the way a boat runs and especially on pontoon boats because they are different props.

Do some calculations on what your slippage is now and that will give you an idea if there's room for improvement. RPM / Gear box ratio x Pitch = Theoretical inches moved per minute. Then divided by 63,360 (inches per mile) = miles per minute x 60 = miles per hr. Example: 5,000 RPM / 2 = 2500 prop speed x 9 pitch = 22,500 inches per minute. Then 22,500 / 63,360 = .3551 miles per minute. Then .3551 x 60 = 21.3 MPH Theoretical. (Or... you could use a prop calculator on the internet but I like the math)

If your actual GPS speed is 14 MPH then 14 / 21.3 = .65 so you have a slippage of 35%. A good prop selection will put a lot of this slippage to good use. I've also found out that the average boat dealer doesn't know as much about props as you might think especially pontoon props. (That's probably an understatement) You could start a thread on the Prop page for other input.

My last prop that I ordered for my 150 hp tritoon, I couldn't get any dealers to agree on what the best one was so I went with what Power Tech recommended and just told the dealer to order the prop. It turned out to be perfect. If it's not just right they have a 30 day return policy for a small fee to exchange it for the next size up or down. Also talk to them about porting and cupping.

Summary of my thoughts (in order):
Make any changes to the motor you're going to make.
Make any changes to the boat you're going to make including polishing the toons.
Gather data at several RPM's and speeds and get with a good prop shop and tell them what you want you're after.

Mark

 

[Old Screwball]

Re: Need more power.

I feel your pain. We traded a supercharged, 70+mph OH-MY-GOD, Screaming Mimi Jet boat for an 18 foot, 75hp, 24.6mph pontoon. Perfect for the family, friends, and Grandchildren. Takes a while for your balls to shrink and for you to forget you USED to have the fastest boat on the river. IF I had a hundred grand I'd have a Cheetah or one of those 500cid deck boats. if if IF.

 

[Silver Eagle]

Re: Need more power.

I'd get a hand held GPS, then run the boat on the lake when the water is calm. Play with the trim. That can make a Big difference. Does your friend have the same motor as you have. Look on his prop ,see what his pitch is, also count the bolts on the clamps that hold the motor. Maybe your motor is to high or to low.How many people do you carry, weight makes a difference. I have a 24ft StarCraft ,it has a 90 hp Merc. 2 stroke, Top speed under idea conditions is around 26.mph.With three adults.