Jack Plate question regarding short shaft vs. long (standard) shaft

[wolfee]

I have a 25hp short shaft Mercury that has been on this boat for years but it's actually about an inch short. The distance from top of transom to bottom center is about 18". A short shaft is slightly short, but a long shaft will probably be too long. I've been looking at getting a 50hp outboard and was wondering if putting a jack plate on would allow me to adjust the motor up to the perfect location? I've never used a jack plate so I'm assuming you mount it as low as you can and then raise the motor to the perfect height? Thanks for any help!

 

[Scott Danforth]

are you measuring your transom at the transom angle, or vertically?

a manual jack plate is just that, you mount the engine and adjust as needed

a powered jack plate is normally used in conjuntion with tilt to adjust motor for depth and other factors.

If it was me, I would run a short shaft and trim the transom down slightly

 

[wolfee]

The transom was already cut down when I got the boat and you can't go any lower and still mount to the transom. (see attached) I want to switch to a 50hp tiller which is harder to find and I will still have the same problem. If I go with a standard shaft with a jack plate, then I can mount the motor and raise it up to the correct height. At least that's what I'm thinking. The top of transom to bottom/center vertically is ~17 1/2 inches.

 

[wolfee]

Am I making sense here? I guess the question is should I go short shaft or standard shaft when I upgrade to a 50hp tiller?

 

[racerone]

I believe you should have a look at the transom.------Perhaps it is full of rotten plywood.-----Repair and build it up to 20" again and use a long shaft ( 20" ) motor.

 

[jhande]

I'm with racerone!
That transom looks a bit scary to me.

 

[wolfee]

That's the new transom. It was basically mulch and I installed two layers of marine grade plywood glued and screwed. The pattern of the transom is probably 30 years old and I just added the aluminum strip along the top. The transom is solid. I really don't want to do it again, it was a pain getting the plywood in. I guess I could if I had to, but was hoping I could put a jack plate and a standard shaft 50hp tiller. Problem is finding one. Thanks for the advice guys!

 

[jimmbo]

Looking at the Picture, I don't have any Confidence in that Transom. It looks like there are several places where water will get in, and torn Fiberglass.

 

[Captain Caveman]

I used to have a 1980s Fisher who's transom was too tall for a short shaft (prop was spinning out of the water) and too short for a long shaft. I ended up getting a section of 2" square aluminum tube and welded it to the top of the transom. It worked great on the 35hp Evinrude that I ran on that boat. I never saw any flex.

 

[wolfee]

It's all aluminum and stainless steel trim, no fiberglass. The bar that looks out of place is just to protect the inside of the transom from the motor screws. The fact it was cut down does allow some water in if a decent size wave hits the transom but like I said, the transom is ~17 1/2 inches to bottom/center/vertical. I'm in the middle of 15" and Standard shaft. The motor is a 15" 25hp Mercury (1989 great condition) but it's slightly too short. I'd like to go to either a 40 or 50hp (boat max hp is 50) but if I buy a short shaft I have the same problem. Standard shaft would require a Jack Plate. At least that's how I see it at this point. Does anyone know if motors are available now? When I last checked there was a huge backup.

 

[freedomwaters]

depends on what the boat is for imo. I'm still learning about mounting and engine placement. If it was me and this is just a fising boat not trying to race to any spots. Id just go with a 20" and trim up a little. It will get you to your trolling spot. I'd also cover it.

if you're set on a jack plate you'll need to be able to access the mounting bolts.... which might give you better deck drainage.

 

[freedomwaters]

found this