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Muskie Fishing -> Muskie Boats and Motors -> Short shaft to long shaft question
 
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Message Subject: Short shaft to long shaft question
Leck9
Posted 5/7/2019 3:31 PM (#937017)
Subject: Short shaft to long shaft question





Posts: 31


I am looking for some advice here. I purchased a 1996 princecraft resorter which has a 20” transom, however a previous owner has cut a notch out of the transom (center of transom now 15 inches) to fit a short shaft motor.

My question is, without rebuilding the transom (wood is still good) what are my options for placing a long shaft outboard on safely.

I am am thinking of installing a jack plate (T H marine hi jacker) that would mount to the original transom and raise the mounting height of the motor by 5 inches (bring it back to 20 inches). I would then run some diamond plate (or other material) across the notch so no water could get in.

any thoughts? Pros and cons to doing this?

any other recommendations would be great.



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VMS
Posted 5/8/2019 6:58 AM (#937050 - in reply to #937017)
Subject: Re: Short shaft to long shaft question





Posts: 3508


Location: Elk River, Minnesota
Hiya,

To be honest, if the transom board has been cut, I would not feel comfortable creating a "patch" (so to speak) to fill the notch in the transom to install a long shaft back on. The notch created will always be a weak point as the integrity of the board has been compromised.

My gut instinct would be to rebuild the transom. Get a new transom board in place, get it sealed and covered back up then you should be good to go.

Without a new board, the filled notch will always have some flex to it, and it would have to be larger than the mounting bolts for the motor.

To even come close to a strong transom by filling the notch, I would think you would need a length thick aluminum that runs well beyond the notch itself from port to starboard (at least 6" on each side of the notch), attached both in front and in back, along with some sort of rods being run vertically.

With any sort of of notch filling, you will always run the risk of humidity changes creating even more problems as the boards will swell differently being different boards, the joints will always be at risk.

I'd say...rebuild the transom... Play it safe and have the peace of mind it's been done correctly.

Steve
Leck9
Posted 5/8/2019 7:59 AM (#937056 - in reply to #937017)
Subject: Re: Short shaft to long shaft question





Posts: 31


Thanks for the input I appreciate it.

I was thinking of installing a fixed jack plate below the notch. I would only run some metal across the notch to fill the space (and no water to get in) but the whole load of the motor would still be on the original transom.

I am debating just fixing the whole transom and start fresh, just looking to see if the fixed jack plate would potentially be a good solution for a fraction of the price? I know they commonly used to allow long shaft motors on short shaft transoms.

Thanks again
mikie
Posted 5/8/2019 8:01 AM (#937057 - in reply to #937017)
Subject: Re: Short shaft to long shaft question





Location: Athens, Ohio
What VMS said. I'd not be comfortable putting anything much bigger than a 9.9 on a transom that has had a quarter of it cut away. You have a problem now, that wan't your creation but up to you to repair properly for the safety of all on-board. m

regarding your up-post, the 'load of the motor' is not just the weight, but the thrust against the transom that pushes the boat. That transom has now been compromised. m

Edited by mikie 5/8/2019 8:03 AM
mikie
Posted 5/8/2019 11:50 AM (#937071 - in reply to #937017)
Subject: Re: Short shaft to long shaft question





Location: Athens, Ohio
Another thought: take the boat to your nearest DNR Watercraft office and ask them to inspect it. Ask them if the modifications you propose will meet state and federal requirements. They would have the final say. You don't want this:

https://www.youtube.com/watch?v=hE1ufZspnEA

m
Leck9
Posted 5/8/2019 1:45 PM (#937075 - in reply to #937017)
Subject: Re: Short shaft to long shaft question





Posts: 31


Thanks for all the input I appreciate it.

I’m going to repair the whole transom and not take a chance
VMS
Posted 5/8/2019 4:17 PM (#937081 - in reply to #937017)
Subject: Re: Short shaft to long shaft question





Posts: 3508


Location: Elk River, Minnesota
Hiya,

The jackplate would be one way around it, but the issue I would see is you may run into is the bolts mounting to the transom....they will be directly under the notched area and potentially the lower bolts will not even be through the wood itself. What the jackplate would also do is increase the "lever" so to speak beyond the back of the transom. With a compromised transom already, you are essentially adding more torque to the remaining portion of the transom. It honestly would not be safe in my humble opinion.

I think as you have started at this point to look into is full replacement... It's your best bet overall.

Steve
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