paulr

Briefly searched but didn't find anything, I'll search again in a bit. I guess I've never seen anything resembling a "performance" trolling motor. I found an equation online, and based on it, i would need 208 pounds of thrust. And I doubt that would be anywhere near 5 MPH. I'll keep my eyes out for 12V units, but after doing a quick google search, anything over 50 pounds thrust appears to be 24 or 36V (A beast I do not want to tackle)

Brian:

Even if it were, the boat has dry exaust and I want the performance that offers, and I would rather use an outboard then re-do the exaust. I also want it loud when I am running .

Even then, the community I live in has a large quantity of elderly persons - It'd take a lot of work to get those 454's as quiet as what I have now, and that is just marginally accepted. That would also probabily cost more than an outboard, and as much as one of the other ideas proposed. I'd rather have a second system (low on fuel / low noise / etc) - and still have the ability to have it be heard when I'm out on the river, etc. On my chris I did go out on one engine, but I didn't think to alternate, so the hours are a bit out of sync.


For the short term or for the long term if necessary, I'll just take the boat out during hours when everyone's up - to keep everyone form getting really pissed. It's just nice to leave at 6 or 7 on a Saturday and beat some of the traffic.

Thanks,
PaulR

Mr. Demeanor

What about diverting the exhaust completely under water? If you do use a prop, maybe the folding low drag types used on sailboats would help. I think electric power may be a good way to go. Even extra batteries or a generator would weigh less than the equivelant engine. If you could get a big enough jet mounted and figure a way to power your steering maybe you could leave a drive down and use it as a rudder for steering.
Im no marine engineer, but I did stay at a Motel 6 last night

mcollinstn

No sort of non-marine engine can be placed in your engine compartment, ESPECIALLY AN AIR COOLED ONE !!! (pretend that there are about seven thousand exclamation points there).

Only something along the lines of a jetski motor or something can be placed inside the boat. And the smallest of those is around 30 hp (the short lived Kawasaki 250cc jetski motor is the smallest).

A side inlet on a jet drive would be more or less do-able, but you now have to run a length of reinforced fiberglass tubing around in your engine compartment. I just don't see it being a "good thing". Nor do I see it being particularly helpful.

Most trolling motor propellors are designed for appx 5mph. I'd say that twin 42 (or 54's if you need them)pound cav mounts would push your boat 5 mph easy, if you were running Alpha drives where the props would freewheel. Bravos and TRS drives will most likely drag the props (not turning) at 5mph (Bravos might spin the props, but I'd venture that TRS's won't). Might still get 5 mph out of her even with the props not spinning.

It would sure be easy enough to find out: borrow two trolling motors, make a temporary bracket off your swim platform, rig two batteries together, and hang the trolling motors securely just behind your outdrives.

If this works, it is your cleanest option. You may need the generator, though, for this to work, cause two of these running wide open for an hour will suck the life completely out of a pair of batteries.

As far as noise, the Honda generator is very very quiet, and you will just pull it out and sit it on the swim platform for your slow ride.

Also, though, you seem to be under the misconception that small outboards are not quiet. You obviously haven't been around some of the modern "silent" 4 strokers...

mcollinstn

Appears to be a "rough" correllation in comparing thrust to horsepower in a lowspeed pusher application:

54 pounds of thrust is roughly equivalent to a 1hp motor.

paradigm shift

Well I have seen Arnesons tunnel with those little electric motors. OK around the docks or to load / unload but you will not get very far very fast. Nice idea just do not think they would work well or you would be happy with that set up.

Probably the easiest is to quiet your existing exhaust. Some type of switchable that would get you under the water would work. Switchable so you can let it rumble in the open water. Saw the sorcerer tunnel a few years ago with some very exotic exhaust diverters. It was amazingly quiet when it was on. Man that thing rumbles when uncorked though!!

Just my .02. Good luck

paulr

If I Can find suitable 12V units, I may go that route. Still not sure exactly how I would mount them, part of the appeal of the origional jet drive idea would be that nothing would be visible with the boat in the water. A second steering Wheele wouldn't be impossible, but not preferred. With the batteries, I plan on installing two 8D batteries in addition to what it already has for Audio Equipment and an Inverter, so those could power a trolling motor as well.

mcollinstn:
I don't think the cooling would be a problem, but that is a point I really hadn't given much thought to until now. I am still mainly interested with the jet drive idea, with the trolling being a secondary. However, if it's mounded on the cav plate, what about the drag while I am under way ? I don't know anyone offhand with two spare trollers, but I can look around. Power probabily won't be an issue, as I will be installing those extra batteries.

Generator is a good idea, but if I am going to be doing this with some frequency I would prefer to mount the generator in the compartment. Again, the heat would probably be an issue.

I have never seen a quiet small outboard, I have seen quiet big ones however. Either way, I don't want to be sitting on the swim platform steering the boat, and I don't want the outboard hanging on the back end while on plain. Whatever I do, I want it to look slick, or as cool as possible. This isn't a 'rush' situation, so I can do the research to get exactly the system I need.

I've seen small trollers mounted on Trimtabs, but have no idea how many pounds they were, or how they affected the trimming. If those have enogh power and won't screw up the trimming, that may be a real option. Whatever I use, it has to be 12V.

At idle (4.6 MPH GPS or so), it takes me almost 15 minutes to reach the river, where I could turn on the main engines if I Wanted. I have another 3-5 minutes until I can actually power up, but this could be done under the main engines if necessary. If a trolling setup could get going 5 MPH for 15 minutes and then charge on the river, it might be an option (and a lot less painful then either the jet drive or the silent exaust - which I am not hot on). Either way, the outboard is my absolute last resort.

Thanks to everyone for all their feedback!
~Paulr

p4-33

OK, so I was off a bit... 33 Daytona, single 1,800 HP Lycoming T-53-13B Turbine, and a 6-drive.. Here's some pics for an idea how he rigged it:

http://www.hotboat.net/classifieds/a...bine%20Daytona

Don't know about the thrust numbers on his, but he seemed to make it work. I saw an article somewhere else about it, so you might do some additional searching for "33 Daytona Lycoming" and see what comes up.

Brian

paulr

Wow brian, that's Quite a setup. It looks rather slick, too. Haven't found too much mention of it on the internet, but I am still searching. Found the main listing. That's a good idea with the hydraulic setup. I just sent him an Email inquiring how he set it up, and how fast it moves, thank you for this reference. Wow, 135 MPH. If anyone else has any more ideas, please post them.

Now that I know about all these other options, I probabily won't consider the jet drive unless I can get enough horsepower to get it up on plain.

Too bad turbines are so expensive....

Thanks to everyone,
~Paulr

mmwalters

You guys might want to check with Howard Arneson or Rik They have done everything you are talking about. Howard's turbine setups do not use a transmission Maybe you can find. something on his web site We did a twin turbine cougar cat with a 90hp jet drive Yamaha with a high lift jack plate but the jet ski setup is the cleanest deal

mcollinstn

No! I could care less how well a lawnmower motor or a portable generator will cool in your engine compartment. That's not even a tiny concern at all.

The concern is that a non marine engine or device in your engine compartment WILL BLOW YOUR BOAT UP.

As in BOOOM.
Wouldn't give a rat's @ss whether the generator or mower motor was cool or not when it exploded your boat into a giant fireball.

Have you never heard of USCG approved devices? They are required in any engine compartment. You know, the engine compartment that gets filled with gasoline fumes from non-USCG generators and lawnmower motors that are bolted in there. That's the one I'm talking about...

And a quick question: you mention you are going to drop 8D's into it and an inverter. What exactly are you planning to do with the inverter? Power TV's and fans? or something more?

If you run a couple of 8D batteries, you can definitely run the trollers with no generator. You can also flip a quick switch and run them on 24v from the 8D's (or from whatever pair of batts you are using). If you plan to do this, though, you gotta use the correct type of battery switches. You don't gotta stick with 12v trollers.

As far as switchable exhaust, there's no reason why you can't adapt a captains call style setup to your boat, which will dump the entire exhaust out the prop hub underwater like a Bayliner. Just a bunch of bubbling sound. No rumble. Flip a switch and you got loud and nasty again. You seem to be avoiding that easy option and wanting to bore giant holes in your boat and mount explosive lawnmower grenades in your engine compartment. i am not sure I understand...

As far as the trim tabs, sure, I see no reason why you can't mount trollers on the tabs. That sounds like a good place for them.

And here's another idea.
How much thrust do you need to make your boat go 5mph? Get a ski rope and a meat scale (it'd be great if it reads up to 300 pounds, but 150 one will do for this purpose). Get a towboat and hook your Scarab to the towboat on the ski rope and put the meat scale on one end. Pull your boat at different speeds and read the towing power required to make it coast at different speeds. You can even drop the drives to see how much it matters. If you can get adequate speed with 100# of pulling force, then the trollers should work. If you need 300# to get the speed you want, then you know you need a 6hp setup.