Raising the transom

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    Posted: 23 Apr 2022 at 5:37pm
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I'm looking for a replacement outboard and have been keeping an eye on the second hand market for a while. I need a 20" shaft engine though, and there isn't much available. Does anyone have experience with raising the transom so that a formerly 20" shaft boat can take a 25" shaft engine?

Anyone know of a place in the Wellington region that does it? I asked Boat City in Paraparaumu and they seemed rather hesistant. Thanks for any tips.

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Post Options Post Options   Likes (0) Likes(0)   Quote Kandrew Quote  Post ReplyReply Direct Link To This Post Posted: 23 Apr 2022 at 6:00pm
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Is it a tinny or glass boat, I went to a long shaft on my tinny, rebuilt the engine pod. The only issue I had was when the engine tilted right up the cowling hit the transum but a spacer in the tilt ram fixed that.
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Post Options Post Options   Likes (0) Likes(0)   Quote davidc Quote  Post ReplyReply Direct Link To This Post Posted: 23 Apr 2022 at 6:05pm
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It's glass fibre, a 6.2m Sea Nypmh Commander.

Guess you're not in Wellington Kandrew?

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Post Options Post Options   Likes (0) Likes(0)   Quote Kandrew Quote  Post ReplyReply Direct Link To This Post Posted: 23 Apr 2022 at 6:20pm
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Originally posted by davidc davidc wrote:

It's glass fibre, a 6.2m Sea Nypmh Commander.

Guess you're not in Wellington Kandrew?

No I’m in Auckland, may not be that easy and not needed anyway. You will need to talk to a boat builder and there’s also a good Sea Nypmh page on FB
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Post Options Post Options   Likes (0) Likes(0)   Quote Steps Quote  Post ReplyReply Direct Link To This Post Posted: 24 Apr 2022 at 10:59am
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Yep been there done that on our Commander.. 5.5m  18' 2"
 See my post on your other thread...
1st establish what condition the transom is inside.. pull screws , bolts even if not still sure drill a couple test holes below water line.
 If not good then replace the transom.. is not as big and complex job as you would think.. just labour... and most that is waiting for stuff to cure.
 Transom good.. look at a simple jack plate.. not a fan on these on the back of the commanders, completely changes the balance of the hull... notice how pod hulls have the helm further forward to counter it.. and loading more weight  just uses more fuel and hp.

That leaves a alloy plate from just above the bung/ bottom of transom, folded over at the top, board inside.. and bolted thru the transom. Then an insulation pad between the alloy and outboard prevent corrision

Somewhere here I still have a heap of pics of lots commanders that have had plates and pods fitted .. some stupid , most sensible. PM if want me to find them on one of my old computers.
 
Ok this part is very important.. pod or just raised transom..
The transom sits at 12.5 degs.. up/increase the height... that moves the prop slightly further out from the transom... The water from under the keel on the plane comes out as an elliptical curve till gets back to actual sea level.. that means the engine will sit slightly higher than if on the transom.
So take that into consideration when doing your calculations..
its not just and extra 5" to top of 12.5 deg transom or 5" on actual vertical height.
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Post Options Post Options   Likes (0) Likes(0)   Quote davidc Quote  Post ReplyReply Direct Link To This Post Posted: 24 Apr 2022 at 1:46pm
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Thank you Steps. Good to know that it is doable. I'm not handy enough to do it myself though - anyone know of a reputable boat builder in the Wellington region?
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Post Options Post Options   Likes (0) Likes(0)   Quote Steps Quote  Post ReplyReply Direct Link To This Post Posted: 25 Apr 2022 at 8:06am
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A local engineering shop can make up plates or plate to fit, just need to bolt on .
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Post Options Post Options   Likes (0) Likes(0)   Quote davidc Quote  Post ReplyReply Direct Link To This Post Posted: 25 Apr 2022 at 9:46am
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Hmm, would just any engineering shop understand the implications of modifying a boat?

If I were to go this route I think I'd want someone who'd done the same on boats many times before. Othermight I might stay safe and cough up for a new 20" engine.

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Post Options Post Options   Likes (0) Likes(0)   Quote Kandrew Quote  Post ReplyReply Direct Link To This Post Posted: 25 Apr 2022 at 10:16am
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Yep your right, as I say in your other post, if this is done wrong your stuck with it for good. I wouldn’t go to just any engineering company to get this type of work done. It needs to be designed properly and installed correctly.

Why do you want to go to a long shaft, I did because at anchor in a swell the bottom of the power head would dip into the water, not good. If your boat is fine with the short leg and after all these years I wouldn’t see why it isn’t, wait for the right motor to come into the country. Old 140 and new 150 will be around the same weight if not lighter.

Have you spoken to a reputable outbourd mechanic to get their thoughts. This is a very expensive upgrade that has to be done right or you will be very disappointed.
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Post Options Post Options   Likes (0) Likes(0)   Quote davidc Quote  Post ReplyReply Direct Link To This Post Posted: 25 Apr 2022 at 6:22pm
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The reason to raise the transom is that there are many more 25" than 20" second hand engines out there. I'd really prefer to get a 10-20 year old second hand engine than shell out for a brand new one, so raising the transom to improve my chances of getting a second hand engine is an idea. If it's too hard or risky I won't bother though. If anyone knows of a reputable shop to do the work in the Wellington region that would be great to know.
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Post Options Post Options   Likes (0) Likes(0)   Quote Pcj Quote  Post ReplyReply Direct Link To This Post Posted: 25 Apr 2022 at 6:57pm
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Originally posted by davidc davidc wrote:

The reason to raise the transom is that there are many more 25" than 20" second hand engines out there. I'd really prefer to get a 10-20 year old second hand engine than shell out for a brand new one, so raising the transom to improve my chances of getting a second hand engine is an idea. If it's too hard or risky I won't bother though. If anyone knows of a reputable shop to do the work in the Wellington region that would be great to know.
Do nothing until you source a motor.
Amateur's built the ark. Professional built the Titanic
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Post Options Post Options   Likes (0) Likes(0)   Quote Kandrew Quote  Post ReplyReply Direct Link To This Post Posted: 25 Apr 2022 at 7:11pm
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Originally posted by davidc davidc wrote:

The reason to raise the transom is that there are many more 25" than 20" second hand engines out there. I'd really prefer to get a 10-20 year old second hand engine than shell out for a brand new one, so raising the transom to improve my chances of getting a second hand engine is an idea. If it's too hard or risky I won't bother though. If anyone knows of a reputable shop to do the work in the Wellington region that would be great to know.
nothing risky about it, just need to get the guy’s to dip it right. I’ll ask around with the engine suppliers I know.
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Post Options Post Options   Likes (0) Likes(0)   Quote OneWayTraffic Quote  Post ReplyReply Direct Link To This Post Posted: 25 Apr 2022 at 8:05pm
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Could consider a fixed jackplate. I have one on my boat that fits a 20” etec on a 15” transom. Multiple adjustment holes. Plate is made from two pieces of extruded 10mm aluminium. I’ll be letting mine go once I fit the outboard onto my new boat.
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Post Options Post Options   Likes (0) Likes(0)   Quote davidc Quote  Post ReplyReply Direct Link To This Post Posted: 25 Apr 2022 at 8:56pm
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Thanks Kandrew.

OneWayTraffic, I suppose if a reputible dealer told me they could do the job I'd consider it. I'm a bit worried about something less than good being shaken to bits over time, and failing out at sea with the wife and kids aboard.

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Post Options Post Options   Likes (0) Likes(0)   Quote Steps Quote  Post ReplyReply Direct Link To This Post Posted: 26 Apr 2022 at 8:03am
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As I mentioned before, you have 3 methods to raisde transom
1/ Rebuild it it .. Its not comp0lex but does require under standing of construction.
2/A heavy alloy plate folded over at the top , raising the engine well, supported underneath top edge and bolted thru the transom.
 3/ A jack plate bolted to transom.
 As the engine head dipping, well I have 150L fuel a 2001 2 S V6 1250 johnny on the back and is fine.
The transom sits approx 1/2 to 1 " lower at anchor with 3 guys fishing over the stern.

As I mentioned above a little bit of basic jnr high school geometry taking into account the 12.5 deg angle off vertical of the transom and the epilical curve of the water at plane from the keel will give you the height required if using a plate , or rebuild transom or a pod off the back. Keep in mind there are several engine mounting heights on the engine, dont go for the top of bottom choose the height for one of the middle ones.

My preference that was going to go for if a 25" leg didnt turn up was the folded plate... 2nd was make up a short (as close to the transom as possible so as not to mess with the hull balance.) fixed jack plate, mounted thru the old engine mounting holes.
 The rebuild transom, well used to do that stuff for a living and have the tools, and as my transom is solid did not justify the time or cost.

1st thing to do is establish how solid your transom is...how mentioned above.. THEN go from there.
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Post Options Post Options   Likes (0) Likes(0)   Quote davidc Quote  Post ReplyReply Direct Link To This Post Posted: 02 May 2022 at 3:47pm
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Thanks for the reply Steps. I'm definitely not confident enough to attempt it myself, so it would be a matter of finding someone local and reputable.

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Post Options Post Options   Likes (0) Likes(0)   Quote Kevin.S Quote  Post ReplyReply Direct Link To This Post Posted: 02 May 2022 at 4:50pm
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I had to get this done to a boat some years ago.  I bought a replacement outboard without realising it was a longer leg than the original (rookie mistake).  I got a local boat repairer to do it for me.  He made a wooden extension piece and fitted it with long mounting screws going down into the existing transom then glassed the whole thing in and put the ourboard mounting holes in.  Solved the problem and looked a really neat job -probably much neater than if I'd tried it myself.
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Post Options Post Options   Likes (0) Likes(0)   Quote kimber7wsm Quote  Post ReplyReply Direct Link To This Post Posted: 03 May 2022 at 6:49am
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Silly question, but can you find a newer version of your motor? If so you should be able to just swap the legs. That is a very simple solution.

Even if you just swap the mid unit, so you still have the newer lower gearbox.
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Post Options Post Options   Likes (0) Likes(0)   Quote kimber7wsm Quote  Post ReplyReply Direct Link To This Post Posted: 03 May 2022 at 6:59am
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Sorry I didn't see your other post saying you want to go to 4 stroke.
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Post Options Post Options   Likes (0) Likes(0)   Quote Steps Quote  Post ReplyReply Direct Link To This Post Posted: 03 May 2022 at 9:03am
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A thought about going new 20" that considered at the time we where looking..
Wife pointed it out actually.
Its an older boat, even thu solid, it will eventually meet its 'end of life'. You now have a 20" that has no real market for..or ability to put on another hull.
 I have looked into this..adapting a pod/ transom from 25 to 20 transom/ pod  and guys here talked me thru much of it, and the number confirmed their advice. Can be done on some hulls but even then its not successful and has inherent issues.. or simply not a good option.

Reason for considering was if I go to a bigger more modern hull, want to keep my 150 20" and put the smaller 25 " on the commander and sell it.

Sorry, but have been told in no uncertain terms the explanations as to why have done stuff just pisses everyone off.. I disagree as that stuff is important to those going thru to make good decisions (???)

End of the day , after several yrs and lot trips...
glad still gone the older low hrs 2S.  And capital cost, going 4S as against fuel/ power etc saves us heaps. Little devaluation.
But where very lucky to find the 20" after a very long hunt around.
The alternative we had decided on was a good 2nd hand 140hp 2S 25" leg then raise the transom, and the method being very much along the lines Keven described above.. building a jackplate 2nd choice.
This is all been said with the advantage of hindsight of going thru the exercise over several yrs and after several yrs.

The big call was if we went new, even if the bimmini was near new, all upholstery close to new, everything in mint condition, no matter what, at best would only pull 10 to 12 K on resale for a commander That sell price not advertised price... regardless if original with war wounds showing and repaired correctly of a new paint covering whatever underneath.
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