outboad hydroplane and motor choice?

[racing fan]

I got a 9.6 ft 3point pickle fork hydroplane its very seaworthy but i got a 4 stroke 2 cylinder 15hp merc. new never used built like this year. it's got a racing lower unit on it but even with that will it have enough power to push it along? It's really heavy even for a four stroke so to run it i would half to make a semi bilge up at the motor but that would be hard and little costly but if it gets it running fine. If it's too heavy can i stuff a two stroke 440cc snowmobile engine in it with a little work or make it a i/o? by the way 440cc produces over 40hp to about 50hp. any help would be appreciated.

[rasorinc]

Most of the members here would not know what a Picklefork is. It is a Glen-L design. Have you posted on their forum this question where people who have built one can lend their experience?

[racing fan]

oops yea, it is like that you can see pictures of a boat that's just like it on http://www.area31racing.com/history/1990s.html its like the 3rd pic. down on the homage it's just a little longer maybe a 1ft. longer. buts its not glen-I's plan the boat i got was just raced it's a little better than glen-i plans but his are still good.

[Yellowjacket]

Do you know the history of the boat, or what class it ran in previously? If not posting a pic of your specific boat would help.

What does the hull weigh, what do you weigh, and how wide is the air trap under the aft section of the hull?

The length is indicative of a lower class boat perhaps a B or C class or SS25. It isn't a D class boat so 50 hp is going to be overkill.

[racing fan]

I do know its history it raced as a c class and for 5 years a d class. the hull weighs about 280lbs. i weigh about 180lbs. the racer i got it from told me he raced it in d class and he showed the motor used. the air trap ain't in the aft section its in the front and its about 4-4 1/2 ft wide and o-5in deep it gets deeper as it should. I also looked it up in old racing archives and sure enough it was raced class d. hadn't been raced in 1 and 1/2 years. i don't plan on racing right now. just want to go fast. it placed first many times in c and d classes.

[Yellowjacket]

That's an odd looking boat, the front end is, how do you say "interesting" to say the least.

Anyway the boat is pretty heavy for a hydro, and a D motor is based on a 50 hp powerhead, so you probably aren't going to push this boat very quickly on only 15 hp. With a 15, you are probably going to go 25 mph, maybe 30 at the most. You need more power or a smaller, lighter boat.

[racing fan]

yea i made a mistake its not that heavy i went out and weighted it and it was about 180lbs but it takes 3 people to carry with out motor because it's clumsy.

[racing fan]

so if the outboard is to heavy could i put a small i/o in it or a small snowmobile in the front with a shaft and a prop just like most inboard hydros? a 440 cc snowmobile produces 50 hp and 550cc is a 75 hp motor.

[Yellowjacket]

Originally Posted by racing fan

so if the outboard is to heavy could i put a small i/o in it or a small snowmobile in the front with a shaft and a prop just like most inboard hydros? a 440 cc snowmobile produces 50 hp and 550cc is a 75 hp motor.

No, putting an I/O system is gong to be a lot heavier than a D class outboard. A Merc 44 cubic inch motor with a racing lower unit only weighs about 120 pounds, and the hull is designed for that weight to be hung off of the transom. If you try to put a motor forward of that it will upset the balance of the hull and it will be nose heavy. It will hunt and dart and could be seriously unstable. If you want to go fast, get the right motor and set the boat up properly or it will be dangerous. You would need to get the weigh distribution to match the original design to get it to work. You can get a short shaft 50 hp 4 cyl 2 stroke merc for between $500 and $750, and that's what you want. A racing lower unit is going to be expensive (more than $1500) and that's probaly the right thing to do, but for your purposes you could use the stock unit and get a low water pickup and that will work ok. You will need a prop with a good bit more pitch too. Sell off the 15hp motor and get the right thing.

[Submarine Tom]

Yeeehaaaaaaa!!!

-Tom

[Yellowjacket]

Originally Posted by Submarine Tom

Yeeehaaaaaaa!!! -Tom

Yea, I forgot to mention that, btw, the class record for a D stock hydro is close to 90 mph.......

racingfan said he wanted to go fast, well here's his chance.....

Just be advised, these kinds of boats aren't lake toys. They're serious racing boats made to be used at high speed in calm water by skilled and experienced drivers. If you think that you can just climb in one and go blasting across a typical lake with wakes and other boats around, you are going to get hurt. Safety equipment, including a helmet, life jacket and a cut suit is probably more than just a good idea.

Remember that F=MA is not a suggestion, it's Newtons' LAW... Water at high speed is the same as concrete...

[racing fan]

thanks but were could a get a merc 44 running for a good price and are the old merc 44 good motors?

[Yellowjacket]

Four cylinder mercs were made from the early 1950's until the early 90's. There are literally a million or more made, so they are easy to come by. Look around on Craigslist or Ebay for a short shaft version and then you will need a different prop and a low water pickup setup. They can be had for anywhere between $500 to $750 or a bit more for a really nice one. The later ones have electronic ignition so they cost a bit more but are more reliable. The earlier ones have a magneto and a cog belt to drive it and aren't as reliable as the later ones.

[racing fan]

thanks and i got another hydroplane kinda of a family hydroplane i will post this weekend its heavy fiberglass and balsa wood sits 4 needs restoration but would a mark 75h be enough to push it around.

[stupidbaker57]

I am building a Hal Kelly hydro. It's a 11.3 3 point hydro. I plan on putting a 400cc motorcycle engine in it and driving the prop via surface drive. I have designed on cocktail napkin to scaled drawing to a wooden scaled version on the back of the boat. I have all the materials ordered and a few more to be custom made by myself. I have pictures of the wooden scaled version and soon will be building the final drive for steel and aluminum.
With this 27 HP engine I should aceive a speed of 48 MPH. If all works out, I'll be building another boat and mounting a honda 600cc water cooled that puts out 13,500 RPM's at peak.
Am I crazy? Maybe, but I've built some 'crazy' stuff in my life and I've made it to 63 years old.