paulr

Something I've thought about, that I would love to hear anybody's opinion / information on - would be adding a third engine - not a third engine of equal performance with a third stern-drive, but a third engine of much lower horsepower.

I had originally thought about using one of those those really small stern drives - but realized that using a third stern-drive would interfere with the two main drives.

We boat from our canal, and have almost 20 minutes from the time we start the engines to the time we can power up. Additionally, we cannot leave early or late due the noise and neighbor complaints. It would be real nice to be able to use something small (like 80-110 hp) to move the boat.

I had thought about mounting a jet-ski jet-drive (or something similar) low on the transom - something low profile that wouldn't drag while the boat is on plain, and wouldn't get in the way of the cross-member between the other two stern-drives. How well do you think this would work ? I know there'd be a lot to do with steering (two wheels, perhaps?) but is the idea at least worth considering ?

I was hoping to build it up enough to get the boat near plain or on plain (with the two stern-drives lifted), but the primary purpose would be to move the boat at idle speed without burning extra gas and pissing off neighbors.

I have a 30' Scarab (See my other posts), with twin 454's and TRS's.

Thanks,
Paul Rohrbaugh

Fightclub

The idea sounds great not sure how you are going to make it work with 2 wheels and another drive dragging in the water.

Make sure to post pictures if you do it.

paulr

Why I wanted to go with a jet drive - Figured there would be little or any drag. Just raise the two TRS's out of the water when you wanted to use it, and I might even be able to get it on plain. I figured I would mount a smaller size engine in front of the other two (Probabily a V-twin of some sort), and run a shaft under the oil pans of one of the 454's.
~Paulr

BadDog

Very interesting topic. On the raising of whatever you install, use a lever arrangement that when the TRS goes all the way up the whatever goes down. Use a rising rate lever so that it does not go down until the TRS is almost all the way up. Perhaps the jet drive is the right track, doubt you would ever get anything above a fast no wake though. Pick up the water through the hull and pipe it to the jet?

paulr

Through the hull is what I've thought about, I've just been wondering about where. You need a pretty big hole to get water in, but I don't want to be forcing water into it from forward motion and causing extra drag. I had thought about bringing it in on the side below the water line. Just "Idle speed" is all I really need, haven't brought the Scarab home yet, but the neighbors complaned about the Chris-Craft with 350's with wet exaust (Under the fiberglass swim platform too!). Those 454's will make them REAL happy...

Interesting idea with the lever, not exactly sure how it would work. .prettymuch sure a third drive wouldn't work - you would need to raise the third drive to go fast - and lower the TRS's. The linkage between the two is right in the way... (unless you had the third drive so high the prop wouldn't be under the hull)

Another issue would be the strengh of the transom. Wouldn't putting a 4" to 6" hole in the bottom create some structureal issues (As well as a similar sized hole on one or both sides)? What, if anything, would I need to do to reinforce this ?

And yes, if I do this I will definetly post pictures.
Thanks,
Paul Rohrbaugh

MACDAD260

What about mounting a small jet drive outboard on the transom so that it is not lower than the keel. It would be under water when off plane and when on plane would be above the water. You could probably tie it into the steering of the outdrives. Hmmm?

mcollinstn

A jet drive would create a HIDEOUS amount of drag.

The pump intake will scoop water up and direct it thru the pump regardless of whether the jetdrive motor is running or not.

I can only assume you are talking about using an outboard of some sort (jet or otherwise), especially since the motors in the 30 Scarab are not mounted far enough apart to allow anything to be mounted between them.

An sailboat-style outboard kicker bracket will mount on your transom and allow you to drop it for your long slow ride to open water, and then it will swing the motor up and out of the water once you get there. There are some newer ones that some pro bassboat guys are using that will handle a 30hp foustroke outboard.

You aren't going to get your boat to plane with less than 100hp, so just go ahead and forget that part of it. And since you aren't going to get it to plane with a 30, you might as well stick with a lighter 9.9 or something.

Another option may be to use a couple of cavitation plate mounted trolling motors and carry a Honda EU200i generator to not only keep the batteries charged for the trollers, but to run a carryon A/C while you cruise slowly in the searing heat. Those boogers are MEGA QUIET.

paulr

hydraulic steering on the drives, so it'd have to be an external system (which could get messy with trimming the drives). Could probabily get it to work with some engineering. However, I don't have things like welders so any work will require some planning. There's also the issue of appearance, so I'd prefer to go with an internal system, even with the extra work involved, unless this proved completely impossible.

I don't have a specific engine in mind (could use some help with that too), but I was hoping to use some sort of a V-twin or perhaps a V4 (a straight engine would be too big, unless it was mounted sideways - which would be really hard). I figured I could get it in the 80-120 HP Range while keeping it relatively quiet (doesn't have to be silent - just no WWII bomber noise) - which would be hard to do with an outboard.

I guess going at 2MPH would be better than running those 454's at 6 in the morning, but I'd prefer to "open her up" and get up to a good 5 or 6 MPH .

Already wrote all this when mcollinstn replied.
I planned on putting the intake on the side of the boat to prevent the drag, most of the sides are out of the water when on plain. I Planned on mounting a SMALL V-twin in front of the engines, it would just be hard to work on them (Seeing as the third would probabily weigh only 120 or so pounds, it could be pulled if necessary). If you think I would only really small horsepower, I could go with a single-banger Briggs or Honda, It'd still be better than an outboard hanging off the back.

I had thought about trolling motors - I've only seen them up to .5HP - would one HP of force even move the boat ? It's currently 8300 pounds, and I DO Want to get going a good 5/6 MPH.

I guess if I am stuck with an outboard sobeit, but I was really hoping for an internal setup.

Thanks for all the feedback,
Paulr

p4-33

I saw a post a while back (OSO?) where a guy had a 36 Skater that he rigged twin Lycomings turbine engines and Arneson surface drives. As you could imagine, this was probably a handful docking anywhere/anytime. I think he (and the Coast Guard) was most concerned about the balls of flames that shot out the exhaust.

He set up a couple of bad a$$ trolling motors on the transom, and lowered and raised them with a couple of jack plates for outboads. He slaved the steering off the drives. Pretty slick.

I don't think that anything you can do will get it close to plaining off, so you should target something with just enough speed to putt around at no-wake speeds. Twins are always better for maneuverability.

Good luck,
Brian

BajaFresh

Wouldn't it just be a lot easier to run a Silent Choice or Q&Q type exhaust? Or are they not available for TRS's?

My Cigarette has Gills with adjustable baffle plates. It's only twin small blocks but not too loud at idle with the plates closed. You could also run just one engine untill you get to open water. Just altnerate engines so you keep the hours even.