Pontoon Boat & Deck Boat Forum

Uh Oh, here I go again with a ghetto mod!

Here's my plan for a home made secondary engine/bow thruster. What could possibly go wrong....

1. Harbor Freight Predator 5.5 hp 4 stroke vertical engine - the kind used on riding lawn mowers. ($125.00) The output shaft will be facing down toward the water.

2. Use an existing hole I have up front between the center and starboard logs where a pneumatic seat is, The hole is about 3" in diameter drilled through marine plywood.

3. Mount the motor on a turntable so that it can be spun 360" to direct thrust. Fabricate a steering wheel above the motor.

4. Use a torque tube and bevel drive gear case from a grinder to drive the prop. Waterproof it - obviously. The prop will be just below waterline and about 3 feet back from the front so the logs will protect it from grounding. Keep in mind my primary use will be forward and reverse, not so much side to side where the logs will obviously impede thrust. The prop will be above the water under full throttle due to the bow pitching up, so no drag.

Like I said,what could possibly go wrong?

Cheers,

Ron

I like projects, and odd ones at that, but why?? This one seems a bit odd to me, unless you are always fighting a strong current.

I need it to allow access to high altitude lakes in AZ that have horsepower limits. I have a lake 2 hours south of me at 5500 feet. When it's 105F in Tucson at 2500 feet it's upper 80's there. Overnight low mid 70's in Tucson, low 50's there. I plan on spending a week at a time. For free.

http://www.parkercanyonlake.com/

Gotcha, interesting predicament.

what do you think top speed could be with that setup? looks interesting....but also how loud would it be?

Somehow reinforce the deck where the motor is to be mounted.. I see that as a weak link.

onlybillhere wrote: ↑

Wed Jun 05, 2019 12:29 pm

what do you think top speed could be with that setup? looks interesting....but also how loud would it be?

If I can get 2 mph I would be VERY happy. I only need it to go from the ramp to a private camping spot on the shore 1/2 mile away. TINY reservoir but any escape from the heat is awesome. I think it would sound like - a lawn mower - but quieter since the deck should attenuate a lot of the noise.

boocat wrote: ↑

Wed Jun 05, 2019 12:51 pm

Somehow reinforce the deck where the motor is to be mounted.. I see that as a weak link.

A good point, but the horizontal loading on the deck is going to be very small since the motor is 5.5 hp. The big issue is the turntable - where all of the thrust is transferred to the deck. It's got to be robust, but then again we're only talking about 6 ft. lbs of peak torque fron this engine at 2500 rpm. Peak horsepower is 3200 rpm. Thanks for your input!

Good luck!

NOW I'm getting somewhere. This right angle gearbox is rated to handle 11hp at 1750 rpm... for $70.00. I'm liking this project now. I'm into $200.00 so far the motor and gearbox.

Here's an assortment of different size turntables that would probably work.
https://tinyurl.com/y4s9z5jm

steve1313 wrote: ↑

Thu Jun 06, 2019 2:08 pm

Here's an assortment of different size turntables that would probably work.
https://tinyurl.com/y4s9z5jm

Thanks, those look good but I'm going to need something heavy duty, basically I've got a lever that is going to try to pop the two pieces apart. A serious unit like this would probably work, and it can be ordered with a 1" hole in the center - perfect for my drive shaft. This bad boy can accommodate 1500 lbs. and weighs 11 lbs. I'll need to fabricate a stout plate to mount this to so that I can spread the load over a greater surface area on the plywood.

I've been wanting a way to do that for years. But it has to be retractable! Cover it with a box to double as a table. When you need the backup.....remove the cover.....drop the drive shaft....and limp your way back to the ramp.

mgarvie wrote: ↑

Thu Jun 06, 2019 6:32 pm

I've been wanting a way to do that for years. But it has to be retractable! Cover it with a box to double as a table. When you need the backup.....remove the cover.....drop the drive shaft....and limp your way back to the ramp.

Yep, that retractable/removable thing is important! I can't get the toon on/off the trailer with the drive shaft in place since it interferes with the trailer rollers. Instead of the complication of making it retractable I'll probably just join the torque tube/output shaft from the engine to the driveshaft with some sort of quick connect. Probably stainless steel bolts and wing nuts - I haven't gotten that far yet but it could be a huge stumbling block. I'm seriously considering schedule 80 PVC for the torque tube, a LOT stronger than you might think, easy to machine, frangible on purpose in case of a direct hit from grounding to protect the motor mount and engine, and of course not subject to corrosion. I'll use a mild steel driveshaft that will bend/deform easily for power transfer to the gear box - once again to protect the motor mount and engine.

This is getting curiouser and curiouser as I descend into the rabbit hole.

I hope you're prepared to make two of them. I have to have one too!

At least detailed steps to make my own.