So as the title says, I just ordered a 37 EFI BackH20 SWOMP SS for my Custom 1648 Alweld.
I was a bit afraid of the size of the motor vs size of boat, but the guys at backwater kinda put my mind at ease.
I currently have a 23 GDLT on the boat as it is, and I'm getting 18 mph empty.
So what do you think? Is this going to be to much motor for the 1658? Will I have to run pods?
Also it's a 16 inch transom, that I'm glad about cause I am ready for the shorter longtail. LOL

Anyways, just looking for some thoughts on this setup. Thanks in advance.

You will enjoy the setup.
I had a 35 GDSD on my 16x48 with a short transom, and it worked fine. No water ever came over the transom.
Your speeds should increase a good bit with the big block.
You will not have to run pods,
I now have a 36 prodrive hangin on the back of the same 16x48 and its almost 100 lbs heavier than the GDSD.

Good move! I hope to do the same in a couple of seasons. I have been running 25's and now a 27 n my 1648 grizzly, not the best combo but gets it done. I am really interested in what the 37 can do on that hull. An extra 40 lbs. up from the 27 is not a biggie; I have already moved the battery up front, a cooler full of ice and brew up front will be good ballast too. Please give a report as soon as you've made the maiden voyage.

Congrats on the new motor. Post a review after you run it.


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Yeah that's my biggest concern is that I'll get backwash over the transom when I slow down to a stop.
Other than that, I think it's gonna be a nice motor. I really like the boat I have and don't want to go any longer. 16 Foot makes it easy to turn around in tight rivers and such.
Anyways, it's probably going to be the middle of next week before it's here. It's just a waiting game now.
I've done a lot of digging and can't find much on a 37 EFI mud motor, let alone putting one on a 1648. I guess cause it's so new?

Congrats on the new rig. Let us know how it does. Mine is getting put on at the end of the month. It's going on a 1658 w/ high transom so i have a lil more breathing room but I have not heard how it does on a GD 16 yet.

I run a 17/52 Alweld with a 35 swomp, It handles great and will outrun custom hulls with the same motor. I have to get pretty wild to bring water over the transom, or try to climb a steep riverbank.
You'll have a ball! It's a great combo that has great speed, load carrying capacity and it handles easy. As far as turning in tight spaces, I've never had a problem with length as long as the banks are 18' apart. Make sure to get a floor and a stand up bar, and WEAR YOUR KILL SWITCH 100% of the time. I hit a submerged log a couple of years ago before I had a stand up bar and was pitched over before I knew what had happened. I watched my boat drive away with my cousin in it. It hit a canoe that had our wives in it and then the riverbank before it stopped.

Good points! My first conventional outboard almost killed me- that Evinrude started in gear and threw me out, and I did not have a kill switch. With all my longtails, I have put the lanyard on even before starting the motor. I have learned to drive mine without a grab bar, but I always wear the lanyard switch. I have always had short transom motors and you learn quickly not to shut the motor while in the water, or to turn too quickly, and to balance the weight in the boat properly, and have all requisite safety gear on (or within reach). If I can hit 20 mph with two hunters and gear with the 35 swomp I will be in heaven- any faster, like the shortail motors, you run more risks hitting 30mph in the marsh. Can't beat the simplicity, reliability, and cost.

After tonights ride with the 23 on the boat, I can't wait for the 37 EFI. I know it isn't going to run as fast as a surface drive, and I've always been ok with that. I've been running long tails for about 6 years now. The places I go and the shyt I run over/through with the longtail, and the fact that one has never let me down, has always kept me from going to a surface drive.
Now don't get me wrong. I have almost went to a surface drive a time or 2, but I've always been glad in the end that I stuck with a long tail. I'm not putting anyone down, because there's nothing wrong with a surface drive. It's just that in my opinion, at the end of the day, a longtail is what's best suited for ME. I don't need to get there at warp speed. I just need to know that I'll get there. Without a problem. Time and time again.
Surface drives may be reliable, but I also drive a 1989 7.3idi diesel F350. Sure there's better newer trucks out there, but the fact that my old hoss is all mechanical with no sensors or computers just means that there's less to brake on it.
I hate to see what'll happen in 10 years when all this new computerized BS starts braking down on people.
EDIT: I know that Surface drives aren't comparable as far as "computerized" but there is more that can go wrong on one as apposed to a longtail.

Florida, totally agree with you on the longtail v. shortail, specially down here. If I could always count on enough water, had big hunting loads and long runs, had to battle a lot of mud, of course I'd buy a surface drive...only after ten years did I have to do any significant maintenance on my longtail, whereas my friend's surface drive MB has needed repairs every couple of seasons. Twice I rode with him we got stuck in the skinny and it was no picnic getting it out, I would have bottomed out sooner with my longtail and gotten back and not shave my prop worthless like he did. I sacrifice 'bout 5-6 mph top end and frankly, I enjoy the ride and get up earlier. BackH20's prices are great compared to GD's or any other longtail mfg., I have to say today's surface drives are overpriced IMO.
When I get mine I will be sure to get an extra prop, seals, shaft, and bearings, from BackH20 though I may not need them for a decade.

Good one! I rode with him as he is my mentor, or the one who "ruined" my life for ever, namely, getting me into duck hunting, and I've been afflicted ever since. He is a coonass from Lafayette and started real young, but like many of us, hard-headed. It was I that convinced him to get a GoDevil back in 1986, it was an 18 HP, slow as hell but we got to the ducks ever since, he never looked back, except in the last few years, a bad back forced him to get the SD. I've got another "role model" down here- a gentleman in his later 70's, who drives a 23 HP LT on a 14' jon boat all by himself and never complains like all the wuss shorty drivers do.

The BackH20 site does not list the 37 EFI yet; some said the price was about 500$ above the 37 non-EFI 35 HP SS motor price? Still a good deal compared to GD and other longtail mfg.'s. I don't see MB listing it yet for their 35's (both the standard and SLT models). I don't mean to be redundant or ignorant but I tried looking online at the EFI and can't tell how or if, this will affect simple throttle advance, which is a cheap "mod" on both Kohler and Briggs motors- meaning to set the rpms at around 4100-4400 rpm out of the water. I'm using both Stabil and Seafoam to treat gas for water and ethanol issues and it is working but wonder what problems ethanol may pose to the EFI? I'm assuming it was developed with this in mind. Will the small motor mfg.'s turn solely to the EFI on all the HP motors? After reading Kohler's link on EFI, the two main reasons are better fuel use efficiency and exhaust emissions standards.

Florida26, I've got news for ya... You won't be too far behind the surface drives. I get 26 out of my rig now that's it's broken in. I don't doubt you'll get 27 out of your new rig. Make sure to post a review when you can. I'm excited for you and can't wait to hear your thoughts on the SWOMP compared to your experience with the GDLT.

I most certainly will post a review along with pictures once I get her up and runnin.
Jake said I should see the 37 EFI by the end of next week. Here's to wishful thinking!

I wouldn't be at all sad if I only saw around the mid 20's with the new motor, however, the more mph the better!

Also, Frank, I am glad you stopped by, as you're one of the deciding factors of my getting the 37.
I see that you're boat is basically the same as the one I'll be putting the motor on.
Do you get any backwash going from WOT to idle over the transom in your boat? How is the over-all handling of your 35? Hard to turn?
I was very worried about getting water over the transom, but after reading a few of your posts, I said to hell with it and ordered the 37. LOL.

No concerns with water coming over, even with a short transom. Handling is smooth as glass, especially once on plane. Slow speed turns require a firm grip on the handle if you have the bump stop adjusted all the way up so the prop sits all the way in the water. Overall no more straining than my old 23 GDLT.

Thank Brycecheramie, good info. Now just have to wait on Florida's report!!

So I just got the tracking # today. Motor should be here friday morning.
Can't wait to get her up n runnin on the 16 footer. I do feel a lot better knowing that frank and his 35 doesn't get any backwash over the transom. You have no idea how much it's killing me to have to wait! LOL anyways, just hang tight and i'll get you updated on it as soon as she comes in.

I know the feeling- try to calm down. Did BackH20 recommend synthetic oil and/ or grease? What grade of gas? All the best, vroom, vroom.

So I got it on the boat today!
Getting 22 mph with me (150) and another person (150).
I tried to drive it by myself and the front was jumping HARD. Will try again tomorrow and post pics as well.

Great! Sounds like some "trim" adjustment needed. Hopefully Frank the Tau will chime in. Dang, that is good for first time, you will no doubt improve that number and level the plane. I've had the flu the last few days but still made it to work, but now I will sneak out maybe sunday morning and run my rig. What depth were you running in? Current, wind? I know I need a "ballast" cooler up front to level mine, it is my "grab bar" after the hunt or run. Have fun!

Where is the cavitation plate riding in the water? It should be just under the surface. It kinda sounds like the leading edge needs to be raised.

Florida, any updates? Inspired by your voyage I ran my motor for the first time since I had the seals and yoke set screws replaced. I hit 19 by myself, lost 1 mph somehow even though the motor has much less vibration. Could only go 1/4 mile into the marsh and then bottomed out- low water is typical this time of year, at the bottom, under five inches of mud, is solid coral rock, no need to bust the prop. With the summer deluges should be fine by September. I'm willing to bet with some adjustment you'll hit 25 with the same load!

Ok, Florida! We need an update on the big block EFI! I'm betting also you hit 26 mph, hopefully you can beat Frank's by a fraction!

im going to get a swomp here soon, whats the price on the one with efi i cant find a number. i got a price on the carb model but not efi. thanks

EFI is $500 more than the carb model.

thanks sounds like efi is the way to go then

Can't wait to join the Swomp club; EFI all the way! Now if only Florida would give us an update!

So I've had it a while and put about 10 hours on it. Still no change in speed. I get 21-22 mph with 2 people and 17 mph with 4.

I really haven't moved the weight around any yet to see if there is a change, I hope to do that this week and I'll let you know if there is a difference.

That is still great, considering the load you are carrying! I know most of us with prior carb models of different HP have adjusted the throttle rpms out of water to anywhere from 4000-4400 rpms, to get an extra mph or so, how is that done on the EFI? Or is it even possible? Is the prop a 9x8? Will turning a 9x7 be any better? Have fun! I danced for rain and we are finally getting some here!

On the 37, the rev limiter is set at 4750, if you prop it to run around 4000 with a load and 4300ish empty. As long as the cav plate is adjusted right, that will probably be your best speeds.

My GDSD makes the best speed at anywhere from 4000-4050 RPM. Apples:oranges, I know.... But same rev range.

Florida, I would keep tweaking the setup, the speeds you are seeing are similar to the speeds I was seeing with the same boat 25hp gdlt. The hopping is the indicator something is not right. On the other hand if you are happy and satisfied just enjoy it.

So I put a Tiny Tach on it, and it's showing that I'm at 400ish RPMs at Idle, and 2150-2200 at full throttle.

This doesn't seem right. It's hitting the rev limiter at like 2400 RPMs out of water. I know for a fact it should be showing 4k plus but its at 2k. Could this be because it's only hooked up to 1 spark plug wire? What gives?

Your right. My OOW idle is 1000 and WOT is 4000. This is on a carbed motor. Let us know what you find out.


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It only is supposed to be hooked to 1 spark plug wire. Sounds likes it's not wrapped correctly, or the tach is jacked up. I'd always lean towards the former, because even though they aren't the best built tach in the world, they should work out of the box. If they don't work, you wouldn't even get a display.

Sounds like it's set up for a single cylinder engine instead of a v twin.

Florida26. Just curious what prop your running. Was told that the 37's were going to have a different prop than the 35.