18' Party Raft needs more power!!!

[StewiackeRiverRun]

Hey Folks,
For the past few years, my friends and I have been taking part in the annual Stewiacke River Run(the first weekend in June) aboard an 18' raft with a full roof, BBQ, stereo, sofa and other seats. This year, we have removed the sofa and decided to add a 167 US gal hot tub! We're afraid that the poor little 4hp Evinrude that has been faithfully pushing us along over the years will not be sufficient with the added weight. We are in the planning stages of gearing up a 9hp Honda 4 stroke engine with a belt drive system...I stopped by the local marine shop and was given a prop for a 9 hp engine, we're wondering if we should drive the prop at a 1:1 ratio, or if we could take advantage of 4 strokes torque and spin the prop at a higher RPM??

Any thoughts on this would be greatly appreciated!

Thanks,
Ronnie

P.S. We are thinking of adding a paddle wheel to this vessel in the future too

 

[Mac525]

Re: 18' Party Raft needs more power!!!

OK I'll bite your going to need a high thust prop like a 5 pitch but we really need to know what speed you are looking to acheve before getting into the gearing or prop. The paddle wheel is a great way for low speed high torque applications sounds like a hell of a good time.

PS only because some one is going to say this if I don't can your craft carry 1900+ lbs of extra weight and raise the center of gravity oh 18 to 24 inches and still be sea worthy ??? please post pictures I'm sure they'll be worth a thousand words

 

[StewiackeRiverRun]

Re: 18' Party Raft needs more power!!!

Hey Mac,
We are using 55gal barrels under the raft...there will be a minimum of 16 of them under her which can carry about 7,339lbs so we're pretty sure that we'll stay afloat. We are not really worried about moving quickly as we will be going with the flow down the river for the most part, but let's say an approximate speed of about 5 miles per hour top speed so we could go up stream at times. OH, we are still planning on using the 4hp Evinrude as well, just wanted some more thrust...and if you check my homepage, you can see a few pictures from past River Runs

 

[Mac525]

Re: 18' Party Raft needs more power!!!

I would get an old lawn tractor for the rear end gear box ie forward and reverse and build a side paddler and use the 4 horse as a power rudder it wouldnt take a whole lot of work. I could not find a high thrust prop for that 4hp. If you could get your hands on on say a 5pitch 4 blade you ll want to run the belt drive between 2.0 to 1 and 2.5 to 1 any where in there should keep you moving pretty good in the 3500 rpm range which with that 9hp honda should be 3/4 throttle. PS a center chain driven rear paddle would be the bomb too

 

[StewiackeRiverRun]

Re: 18' Party Raft needs more power!!!

Thank you for the input Mac! You have some great ideas there for the paddle wheel too! If you lived closer, I'd invite you aboard for a cruise.

 

[Mac525]

Re: 18' Party Raft needs more power!!!

post pic's of all the girls IIII mean boats.. I would love to go and have lobster beer and boats especially in a hot tub paddle wheeler too cool