Short shaftmotor on a long transom?

I might be looking for an outboard in the soming days. But ven now as I look around there seems to be an ovewhelming majority of small outboards with the short shaft as compared to a long. Is it possible to mount a short shaft on a 20" transom? The obvious concerns would be the ability of fresh water to cool the thing.

What had me thinking it might be possible was watching a Roland Martin fishing show in the keys for redfish he has this neat jack plate that elevates his outboard so the prop is just under the surface allowing him to run in shallow water. It got me to thinking that if a huge 250HP motor could be jacked up like that and run a flats boat, I might be ok with a short shaft if the water intakes were low enough on the motor. An added bebefit might be a shallower draft of the skeg and prop, mine have always hung way below the boats floor.

Or.... am I just plain crazy for thinking about it?

it depends on where you water pick up is. on my 225hpdi the pick up is on the bottom front of my nose cone (below the prop)
having the prop that high will also affect your hole shot. the deeper the prop the more lift you will get

More lift would equal getting on plane quicker correct?

yes..
I have a manual jack plate the i can raise or lower my motor 6" but i need A set of wrenches to do this and for the boat to be on the trailer.
I want to get a hydraulic one that I can change the motor level on the move.
Lower it for the hole shot then lift the motor for speed and shallow water

You missed one thing with Roland Martin's boat. Normally, everything Roland Martin does seems to be a sales gimmick, but that jackplate is an item used in probably 95 percent of true bass boats. Yes, it does raise it up, but what you didn't notice was setback. That thing is set back, probably 10 inches or so (what boat does he have, nitro Z-9?). That is what allows him to run the motor shallower without it ventilating. Now, his boat is a performance bass boat, as is the one Redbug mentioned with the 225, so they are designed to run on pad, which is a very small aft section of the hull. Your aluminum isn't going to do that. The whole real reason for the jackplate is to get less motor in the water, as the lower unit is drag as well. So, yes, you could gain some speed by raising the motor on your boat, but it is going to be very slight. Also, on your shaped hull, I bet you would notice a lot of cavitation on turns, and you would have to build or buy a setback plate. Plus, your boat, being a small tinny, isn't designed to hold a motor on that much setback. Generally, boats with setback, be it bass boats, or larger plate alloy aluminum boats, are designed with that in mind, and special efforts are taken to strengthen it enough for that.

So yes, it could be done, with the proper setback, and likely lowering it some (there is a formula for how many inches you can raise the motor above the standard setting, with a certain amount of setback), as you would need a lot of setback to get that to work right behind your hull.

However, the practicality of that is not so in this case, trust me, I thought about it on mine, back when I thought I wanted a 25 on it, and it just isn't worth it.

There's a fixed jack plate that only space the motor back about 4 or 5 inches.It's adjustable but it has to be removed,repositioned,and bolted back down.I think I saw it on Big Mouth Boat Supply or Vetus website.You could notch the transom,but that would make it be a pain to mount a long shaft motor.

https://www.bigmouthboatsupply.com/1892481.html

https://www.bigmouthboatsupply.com/1892482.html

This is the adjustable one I was refering to.Handles up to 35HP
https://www.bigmouthboatsupply.com/3428890.html

I tried the Vetus Marine sit but it won't load the catalog.

That first one that ben2go mentioned is about garbage. From the reviews I had read on it, sounds as if it is suited for a 30 pound thrust electric, not a 15 horse outboard. The third one, from what I have seen, looks good, but keep this in mind. You will need enough setback to allow the motor to tilt up properly. I am making a kicker mount for a 4 horse 15 inch shaft on my 20 inch shaft boat. Even though I am spacing it only 5 inches down, I have to set it back a minimum of 10 inches to allow the motor to tilt even to the point that the skeg is just barely above the bottom of the hull, where it would be out of the water on plane, and still in the water at rest.

Well, the whole point was to see if I got better deal on a short shaft motor that would work, not that I am LOOKING for one. So it appears (as is usually the case) that there really isn't a way to do it without making problems or more costs down the road.

Just a guess but I'll bet if Roland Martin was fishing the keys for Redfish his boat probably had a tunnel hull. You can run your motor higher because there is a source of water in front of it.

flounderhead59 said:

Just a guess but I'll bet if Roland Martin was fishing the keys for Redfish his boat probably had a tunnel hull. You can run your motor higher because there is a source of water in front of it.

Click to expand...

Good point. I blatantly assumed he was mentioning Roland's Nitro.