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 Longtail conversion to 20" transom 
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Joined: Wed Jul 24, 2013 9:16 pm
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Location: Deep East Texas
Post Longtail conversion to 20" transom
New to the forum, and it pretty much seems that ya'll know what's going on. I've used the search function, but seem to come up empty on the subject in need.

I have a home built 25hp Kohler longtail (72" shaft, prop was sized by what Arlon said it should be - can't remember exactly what size/pitch) that is now on the 2nd hull - 1st being a 1648, the 2nd now a 1452. Both hulls being 20" transom.

Neither hull would move over 10mph loaded with 2 people, Lab, gear, and blind - actually closer to 7 according to GPS, although the 1452 would try to plane out empty (with the dog, of course - she goes where the boat goes - LOL!).

From what I understand, this motor should easily plane either hull out.... Motor was originally set up to run propane, but being a Small Engine repair shop owner, I converted it back to gasoline (besides, have you ever tried to get propane reasonably priced on a weekend??)

I was talking to the guy that built the Longtail, and found out he had built it based on a 'devil for a 16" transom. From what I have been able to find out, the cavitation plate is set to a different angle for a 20" than that for the 16" transom. BUT, I cannot find out what the difference in that angle would be. I've seen all kinds of talk about the angle, but no indication of what the angle difference may be.

Can you help me out? I've suffered losing prime duck spots too long due to being passed up by guys who's boats move faster.....

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Fri Jul 26, 2013 7:29 pm
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Location: Slinger, WI
Post Re: Longtail conversion to 20" transom
Cut the transom down. Problem solved. Put it back on the longer boat too.

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Fri Jul 26, 2013 8:38 pm
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Location: North Central KS
Post Re: Longtail conversion to 20

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Sat Jul 27, 2013 12:56 am
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Location: south Florida
Post Re: Longtail conversion to 20" transom
Get up earlier! :) Sorry, could not resist saying that! I have done it for years. Of course they are right about cutting down the transom. It is a shame some have actually moved to bigger block motors (e.g. shortails) because of this race mentality to get to the "hotspot". Heck, I am simply thrilled to hit almost 20 mph with just me and 17.5 with two hunters and all the hunting gear, and I get there reliably and safely and we enjoy the ride there and back but especially when the motor's turned off and it's just the birds and the call and the scattergun and the splash. I've had a short transom and longtail 72" since '89 and that is enough for me.

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Sat Jul 27, 2013 6:20 am
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Joined: Wed Jul 24, 2013 9:16 pm
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Location: Deep East Texas
Post Re: Longtail conversion to 20" transom
Well.... LOL, Glades - had been doing the "get there earlier" thing for a couple of years, but quit when the "young guns" figured out how early I was getting out, so then I went earlier until the point I was finding all the ideal spots already taken at midnight - my boat is not all that bad to sleep in, but the older I get, the more comfortable my own bed becomes..... Besides, we know the "spot" is not the all of a good hunt - knowing how to call and a good layout can turn a less than desirable spot into the "honey hole" of the day ;) . I would just like to get my boat from the 45 minute trip to the hunting spots, down to the 20-30 minutes like most the other guys with longtails.... 7 mph makes you feel like you are a barge next to a cigarette boat....

I have considered cutting the transom down, but it sure seems like it would be a lot easier to reset the angle of the cavitation plate, if indeed that is all that is required. GoDevil offers a retro kit, but who knows what is in it? Without a 'Devil serial number to a specific name, you can't order their parts...

As for sticking the longtail back on the longer hull, that would be a poor move, IMHO - the shorter, wider hull floats in a lot less water, and gives better stability for blind hunting (and flounder gigging), which is why I got this hull - I decided several years ago that I'm too old for the "stash the boat and stand in the cold water hunting trips" - that Dearborn heater sure is warm, and perks a great pot of coffee on those cold days. When I can drive fully loaded into, and back out of, 8" of water (at an idle and not gouging the motor) - that says a lot for us "old guys".

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Sat Jul 27, 2013 9:12 pm
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Post Re: Longtail conversion to 20" transom
Funny! Waders are definitely for the young and foolish.:) I have a hardheaded friend who struggled with a 1652 seanymph 20" transom and the LT. After he finally gave in an cut down the transom it was like night and day...of course he tired of the exertions on the LT and bought a shorty 35 and cruises in style much faster but the shorty came with the trade off of more repairs and expense. If you have not already done it, advance the throttle and gain a few hundred rpms and maybe 2-3 mph depending on other factors. You definitely have colder weather than down here, we are always packing ice. :mrgreen:

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Sun Jul 28, 2013 6:46 pm
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Post Re: Longtail conversion to 20" transom
Looks like I'm going to have to cut the transom down, since it seems there is no other readily available option available :cry: Early Teal season is just to close to not have the boat ready.... Besides I have it stripped down and headed to the welding shop to install the flotation pods, might as well have him fab up the transom too. I sure was hoping there was something I could do to the longtail instead.

On another note - one of the biggest reasons (other that fuel availability) from changing it from propane back to gasoline was the 15% loss in HP, besides I could tweak the governor to add the extra RPMs ;) . Waders are not necessary (for warmth) here for Early Teal, and up to towards the end of our 1st split (Thanksgiving), unless we are setting up our spread, or the dog won't do her job - on RARE occasion she thinks she is a princess and WE are supposed to get the ducks :shock: - like she's only there for the boat ride, LOL! For the most part, it's hippers, or tennis shoes and shorts (and cans of bug spray). Come our 2nd split (2nd week of December) - it may be a totally different story - I've seen several times I have had to bust the ice with the longtail just to launch the boat, unless I've gone to the Gulf Coast, then it's back to the tennis shoes and shorts (plus bug spray) LOL.

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The key to a successful marriage?
Give a man a 4X4 truck, a rifle, a shotgun, a Mud boat, and a fishing pole - he will be out of your hair most of the year...


Sun Jul 28, 2013 9:26 pm
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Post Re: Longtail conversion to 20" transom
Pods? Again, why not use the 16 footer instead? I would be sure that the 16 floats higher in the water than the 14..... I dont know the math formula to figure it out but common sense says that more surface area = floats higher (especially with a load in it).

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Sun Jul 28, 2013 10:14 pm
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Post Re: Longtail conversion to 20" transom
Didn't you know pods are "cool"? Everybody who's anybody has them (or wants them) ;)

By simple math, the 1648 would have a little more than 1 sq ft of surface area than the 1452 - but reality was the 1648 was a heavier, semi v hull - the taper of the semi v also reduced surface area, plus the weight - resulting in a much deeper draft.

I am wanting the pods to help keep the bow down (or stern up) when navigating shallow water - right now the back end of the hull will drag in shallow water when it's just me and the dog (which is a lot of the time) - even though I distribute the gear, I still can't reduce the draft of the weight of me and the motor in the back end, and I only push 145 lbs soaking wet, and that would be with my waders full of sweat...

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The key to a successful marriage?
Give a man a 4X4 truck, a rifle, a shotgun, a Mud boat, and a fishing pole - he will be out of your hair most of the year...


Mon Jul 29, 2013 9:37 pm
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Post Re: Longtail conversion to 20" transom
Well the mod v was something that wasn't mentioned till now.... Important factor. Carry on.

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Mon Jul 29, 2013 10:51 pm
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Post Re: Longtail conversion to 20" transom
I run a 20 gdlt 72" on a 1848 with a 20" transom. I also run the same motor on a 1448 short tramsom. On the 18' I just bend the cav plate up on the end. It seems to run just fine. I GPSed it at 16mph with all my bowfishing equip and 2 other adults. Haven't GPSed it on the 14' yet. Try adjusting the cav plate before you start chopping the transom down.


Tue Jul 30, 2013 5:24 pm
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