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motiondave

Transom Height cutting down......

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Hello good people, I have a question and I sort of have an answered my own question, but...here we go.

Im looking at old fibreglass boat,12 foot,  that , I think , has long shaft transom. Ive asked the seller to take photos and do a measure.

OK, I know its ok to go from short to long shaft transom, as Ive seen that on my brothers boat. He went from a 40 hp evinrude short to a 80hp yamaha long, via a transom replacement. 

Apart from the well design at the back, of which Im yet to see a photo, and also how the well looks to see if I can cut down the transom to fit a short shaft on it. As the motor supplied is a long shaft and is cactus, and I have a good short shaft motor for it.

Id say ive answered my question by waiting to see photos and a measurement.

Still, has anyone got long to short transom before?

Kindest Regards, David.

 

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Posted (edited)

David. In the past I have converted boats both alloy and glass from long to short and vice  versa I currently have a Pongrass half cab with standard short shaft transom and I have a extra long shaft 26" 90 hp Johnson motor on it.

This is done via a alloy plate that I made up, look up " jack plates " . I am not suggesting you but a jack plate as it would cost more than the boat is worth but any motor can be fitted to any transom ( within reason ) .

PS most old glass boats had standard 20" transoms.

Frank

Edited by frankS

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Hi Frank, 

I think David is asking for advice for the reverse situation -   he thinks he may have a long transom and wishes to use a standard leg motor. 

Personally if you have a high transom, I would not be chopping into it to fit a short leg motor. There are many advantages in having a high transom in a following sea or in being hit by chop stern on.  Possible options could be an ally motor bracket - I have seen these made out of tube and plate (but that will change your stern flotation dynamics as the motor is hanging out there) or a small ally pod... which will give you some flotation, a lower motor mount and a slightly longer water line ... and still preserve the transom height.

Cheers Zoran

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Zoran. Agree cutting chunks away from a transom is not good practice, partly why I suggested he look up " jack plates " as it might give him something to think about.

Frank

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There are mini jack plates available which would suit you boat and motor and that are quite affordable. It's not hard to make your own out of aluminium angle either.

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18 minutes ago, kingfishbig said:

There are mini jack plates available which would suit you boat and motor and that are quite affordable. It's not hard to make your own out of aluminium angle either.

Thats it... I called it a bracket, but you've refreshed my memory Adrian ...  they're jack plates... and you can install them to raise or lower your outboard.  Some sit pretty close to the stern so not too much weight impact.

Cheers  Z

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Thanks people. I just got back to this. I see what you mean

 Leave long shaft transom in place, bolt on jack plate and hang short shaft motor on that. Makes sense. Obviously the concern is water going into cowl, but saying that, at 10 knots in my old pongrass, the ass of the boat is sitting low and water is almost lapping the cowl. 

I will look more into it. 

The boat I'm looking at has 25 HP Johnson supplied but the seller is going to check measurements for me. Plus get some pics of the well.

The boat is being looked at purchase for the wife. Something for her to putt around in. 

She also looking at a jetski instead....but she knows it's limited areas for jetskis. ( Time to hire one out to test). 

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Posted (edited)
25 minutes ago, motiondave said:

Obviously the concern is water going into cowl,

You would have the same concern if you chopped the transom .... the cowl would be the same height from the waterline ... in addition you'd now have a lower transom also closer to the water line !

Cheers Z

Edited by zmk1962
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Another problem with jack plates is that you don't get the tilt clearance , the motor being lower as it tilts the cowling will get pretty close to the existing transom. Much easier and better to get the right size shaft for the boat.

Frank

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Here's a couple of shots both converted from standard to long shaft.

 

Scan0024.thumb.jpg.0c32bfd73401614be1815e091c7bb21d.jpg

Scan0023.thumb.jpg.2fdb5c6222754ec677e93c3df7e66099.jpg

incase you are wondering, I used to use that plate to transport boats from one place to another and would swap from trailer to trailer, yes I know BAD BOY.

Frank

 

 

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