Kicker motor transom height

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Shaugh

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I'm mounting a gas kicker on my 16 foot StarCraft. The boat requires a long shaft on the main engine, but does it need to have a long shaft kicker motor ?

In the position I would mount the kicker, the transom is shorter. If I lay a straight edge along the bottom of the boat in that off center position, the cavitation plate on a 15" motor is 1" below that line... will that work ok or do I need to look for a long shaft conversion for it ?
 
Are you using a kicker bracket or mounting directly to the transom? I don't know the configuration of your transom, but if its like my 14' Starcraft the transom is straight across. The issue I see you possibly having is that your motor may not come out of the water enough even while tilted up to the max. That is one reason to use a retractable kicker bracket. I imagine the kicker will work fine in use but while it's tilted up and on plane it may drag in the water.

On my Sylvan the transom is dropped for the main, so I don't have to use a bracket. This is a longshaft motor and it works perfect. When the motor is tilted it's just enough to be out of the water. But once upon a time I had a short shaft kicker on my Starcraft and it dragged in the water when I was on plane. Sorry, I don't have a picture of that setup.

20180620_180555-M.jpg
 
Yes that's a good point.. it seems to clear when level but I'm not sure it will on full bow rise with the main motor accelerating... I may have to go with a bracket and that would solve the question I guess.

Am I right in assuming as long as the cavitation plate is below the bottom of the boat in that off center position it won't starve the prop at full throttle ?
 
Use of a kicker motor on a larger boat is never going to cause the boat to plane. The water level will never be as low as the bottom of the hull. I carefully measured the distance from the top of the transom to the bottom of the hull on my Jetcraft 19. I dutifully bought a used long shaft Honda. When running the engine, especially from the tiller, the cavitation plate is a good 10-12 inches under water. For a main engine this distance is important. For a kicker motor you just have to get in the vicinity.
 
Shaugh said:
Yes that's a good point.. it seems to clear when level but I'm not sure it will on full bow rise with the main motor accelerating... I may have to go with a bracket and that would solve the question I guess.

Am I right in assuming as long as the cavitation plate is below the bottom of the boat in that off center position it won't starve the prop at full throttle ?

ppine said:
For a kicker motor you just have to get in the vicinity.

Yes, what ppine said. Are you just using it to troll? My kicker never sees much more than just above idle. Full throttle is the job of the main.
 
One other thing to consider is that a short shaft will make reverse a pain since the water will be hitting the transom, it acts like a wall. Personally I'd go with a long shaft motor. Worse case scenario you'd have to buy a transom mount.
 
I like to fish from spot to spot... sometimes I like to get a few hundred yards to the next spot with the kicker at full throttle and remain in the back of the boat.

I know for a fact the time I tried to put a short shaft 7.5 horse motor in the center of the boat to use for the day it didn't allow me to go much above idle before the prop starved out. But if you look at Jethro's photo that might explain it better. His boat is just like mine except his is notched out for the main. Mine is just a long straight transom. Where the kicker motor would be mounted the transom height is effectively lower.. because the bottom curves upward. A short shaft motor in that position has enough length for the prop to be fully below the boat. The cavitation plate will be 1" below a straight edge along the bottom.

I guess I'll just go try it... I thought it might already be well understood.... I'm just not sure if the boats forward movement will somehow still create a turbulent area there and still starve the prop.
 
Shaugh said:
I like to fish from spot to spot... sometimes I like to get a few hundred yards to the next spot with the kicker at full throttle and remain in the back of the boat.

I know for a fact the time I tried to put a short shaft 7.5 horse motor in the center of the boat to use for the day it didn't allow me to go much above idle before the prop starved out. But if you look at Jethro's photo that might explain it better. His boat is just like mine except his is notched out for the main. Mine is just a long straight transom. Where the kicker motor would be mounted the transom height is effectively lower.. because the bottom curves upward. A short shaft motor in that position has enough length for the prop to be fully below the boat. The cavitation plate will be 1" below a straight edge along the bottom.

I guess I'll just go try it... I thought it might already be well understood.... I'm just not sure if the boats forward movement will somehow still create a turbulent area there and still starve the prop.

If that is your biggest concern I doubt it will cavitate enough to create starvation problems. I can't imagine so. What horsepower kicker are you planning on mounting? With my setup I am pretty sure I wouldn't have any issues but my boat is close to 4000lbs. I haven't even tried it, but I would guess full throttle would be about 5-7mph with my 6 horse and there's no way it would be sucking air at those speeds.
 
I'll try it with the same 7.5 that I had mounted in the center when my 35 was out of action, and see if it improves off center... I was a little angry when I got home that day and then realized all I probably needed to do is move the motor over a few inches.
 
I am getting ready to do a long trip on a famous reservoir. Planning to use the kicker motor a lot of the time because they are fuel effecient. Slow speed is the way to see new country. I also plan to use it on my brother's drift boat for salmon fishing. May build a motor mount on a 16 foot cataraft frame and use it for that boat also.
 

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