Why is it that the GTRs should be run at a 20* angle. I have read thread after thread and I have found conflicting information. Some people say that not enough angle will cause you to lose speed and some say it will not affect you at all that it only allows you to trim down lower and dig more. Have heard that it's due to a shim that GT uses for there belt. I don't know what to believe. Someone with true knowledge please set it straight. I know that GT has a reason for building there boats this way I just would like to know why. Again I have read MANY threads and I haven't found the CORRECT info.

Nobody knows. They just kept trying angles and heights until they got it right.

The real reason is because the motor is built for a 20. If you try something different you will sacrifice something.


Don't over think it

Fellas don't take this the wrong way because I appreciate the info but that doesn't tell me anything...especially dguidry...i understand that they are designed at 20* or more depending on who you ask but my boat was built with a 16* I didn't order it like that it had a beavertail on it and I wanted the GT so they ordered me one. Wasn't aware of the transom issue

My transom angle was for a mb originally. I now have a gtr on it. Just play with the trim pin (there are three holes to choose from) to get the angle right. Mine is currently in the middle pin hole. It'll trim up out of the water while underway, and trim down plenty. If I need more down angle, I'll pull the pin and put it in the bottom pin hole. That adjustment serves the same purpose as changing transom angle. If that adjustment wasn't available, then transom angle would matter more.

Their transom angle allows the motor to trim down for reverse plenty, and with the adjustment holes to come up as far as it would need. Everyone pretends these things defy physics and geometry, and break hydrodynamic laws, but they're just boats with propulsion. There is a sweet spot for every boat and load, and unless the rigs are setup exactly the same, that transom angle can be within 4 degrees and not have a problem.

So thanks for the info here is what it boils down to...I am running the correct transom height (21*) and at a 16* angle...the gator tail runs a 20* on a 21" transom (tall) the difference and issue is prop shaft vs the water level. With the proper height of the transom the lesser degree = a higher prop shaft and less prop in the water trimmed out ...the fix is to chop the transom down and inch or so to get the shaft in the right position.

If it mattered so much that you need to cut your transom, the difference in effective height between a 20* and 16* angle on a 21" transom would be less than .1"
(And yes, there is math to support it, as well as experience from myself and many others).

Cutting an inch would put your prop lower than what is considered ideal, but not enough to warrant doing it or not doing it. Cut an inch or not, you aren't going to see any difference because of those measurements. Adjusting the trim pin will solve any angle issue you're concerned about.

I've adjusted the trim pin no gain 26 all the boat runs 1648 buddy has a 1754 runnin 30 with a chewed prop

I don't see how the pin will affect it. That only allows me to trim down lower it doesn't put the prop shaft in line with the boat my belt housing sits 2" above the bottom of the boat every gator tail I've seen has been real close to level

Not trying to argue I'm trying to understand if I don't have enough lower unit in the water it don't push like it should when trimmed up right

A 4 degree angle difference on identical boats with the same motor isn't worth 4 mph. I'll step away and let others try to help answer your specific question, but I got a suspicion you've got something else going on that's causing the disappointing results.

height is more of an issue than angle. Angle can be adjusted Via trim pin locations, The 20* is wthe best of both worlds for Maximum thrust in mud and trimming high enough for running clean open water. I have ran a GTR on a 15* transom with no speed issues. I couldn't trim as far down as a GT boat.

Ok but what is for transom height

It is designed for 20*. You have 16*

Put a 4* shim in and then you achieve optimum performance.

Done deal.

Will it work some other way? Sure...

But it is designed for 20* and it is easy to correct that.

As stated-don't overthink it or try to reengineer the motor.

You can buy shims on ebay or make some.

Call GT if you have other questions and I'm sure they will be glad to help you .

Talked with GT this morning before posting my solution

If the solution you are referring to is cutting your transom down as opposed to just adding some shims, then well.... more power to you.

Still not sure how cutting down your transom is going to improve you transom angle, but if you have it figured out great on you.

I would go with the shims but that is just me. Playing with pin placement and trim aren't (IMO) the best option either. You are not truly correcting for the transom angle being off and doing those two will not give you the same thrust angle that the motor was designed with. Will it be close? Sure. Will it work? Sure? Are opinions like assholes? You betcha! I have one and it stinks like everyone else's.

Good luck on your fix. Hope whatever you try works for you.

26 in a beavertail boat sounds right

A couple pics

One more

transom is to tall

Motor looks way to short for that transom highth

I'd cut the transom about 3 inches are so.

Ant the transom does measure 21"

That's the plan

Update...takin advice I dropped the pin down to the second from bottom and loaded the boat 3 guys (700 lbs) 4-5 dozen decoys guns gear blind fuel All shifted to the back of the boat as far as possible to get the ass to squat up river running against a hard pulling tide 25-26 mph can't get the ass down empty chopping the transom first week of the year 1-1.5"

Still I would not expect 30

Why not duck

Also I've learned not to expect anything but i would like to know why you think it won't run that and what would you expecy

Because every boat that I got in that ran "30" stock ended up running 27-28 the day I was present.

Oh I understand that and I promise if mine doesn't run it i won't lie got no reason to lie especially when your going to eventually get busted by sineone

Update 2 the next morning...2 man (450) 2 dozen dekes gas and gear 27 mph deep water run put buddy on the bank and ran 25-26. this doesn't make sense to me just giving updates so if anyone sees anything that throws up a flag about anything other than the transom height. I will be moving the gas tank to the rear as well.

No not yet that's why put in there if there was something anyone saw about me taking weight out the boat and it slowing down I have to wait until first of the year to get it cut you know Christmas and all

I don't want to cut the transom and then still have work to do if there if is anything else I may need done I want to do it all at once so if you have anything else I may need to look at let me know