Okay...I didn't buy the longtail for the speed, but something just doesn't seem right.

20hp beavertail on a riveted 1436. Brand new 9x5 prop from backH20, just me (250lbs), a gas tank and a battery and I am getting speeds around 17 mph. With a load (above plus decoys, bags, another hunter about 225) it only drops to around 15 mph.

This is my first LT, or any mud motor for that matter, and after 3 seasons it has gotten me through some nasty spots with little to no problems. I'm trying to decide if I want to buy a new motor, new boat or both. In trying to figure that out I'm just wondering a couple of things....

1. Will this motor still perform about the same on a little bit bigger boat with a heavier load?
2. Are my expectations on speed too high? (meaning is this motor/boat combo right where it should be)?

Any help would be greatly appreciated....

Right where it should be. as long as you stay light with the boat, another couple feet and a 6-12" of width won't hurt at all. Will carry the load in shallower water, and may pick up a little speed (it's a longtail, don't expect much more on speed).

Yep what Russ said....

What you could do is get ya a tiny tach and look at what kind of RPMs the motor is turning at WOT; It sounds like your engine is performing to the best of its abilities but the tach will confirm this... especially with a new prop...

If your looking for more speed , you'll have to go with a larger motor . A bigger motor will weigh more on that boat. . In a perfect world even with a 35 swomp on a longtail made boat 26 mph is about tops .

H Finn

Thanks.... Makes me feel much better!

So making sure I understand what Russ said.... A little more surface area on the bottom will help me in shallow water? Makes sense, but my logic often defies science... Hahaha

Yes. Can come from width or length or both. There is a point where width will be a bit counterproductive due to weight and resistance. Length will usually not suffer the same penalty.
I'll do some math for you to elaborate in about an hour (but to be driving).

Yeah.... Let me know what you come up with. It's so far over my head I wouldn't know where to start.

where would i hook the tach up and what should i be looking for?

Be careful how much weight you put in the 1436. I flipped that exact same rig in 2011. Not fun.

Like this?


Hahaha

The tach will have two wires, a black one that grounds out and a red one that will wrap around one of the ignition wires below the boot... RPMs should range anywhere from 3400-4200 at WOT... This just confirms your engine is wrapping up all the way...

I would consider a longer boat before an engine upgrade.
I was running a 1448 riveted jon with a 23hp go-devil on it. I saw about the same speeds you are seeing. 18mph empty with me (165lbs) in it. Loaded with two guys, dog and decoys about 14-15 mph.

This year I upgraded to an 1856 go-devil boat with a 27hp. Runs about the same speeds empty as my 1448, but I can load three guys, dog, tons of gear and will still push 15+mph. The 1856 is a much heavier boat, heavier engine but due to the amount of area on the bottom drafts less water than the 1448 did.

I just went to a different prop on my 1548/20hp setup and picked up speed and load carrying. I was running a 9x6 with some cup work and was turning 3850-3900 by myself at around 19.5-20mph. Went to a 9x4 with some really heavy cupping and am turning 4250 sometimes more and back up to around 21 bumping 22mph. Me (250) buddy (185) 80lb dog, 5doz decoys, guns, ammo can of shells, batteries, 10gal of gas, still held 17-18mph and turned 3900+. Adding one more 180lb guy and his junk dropped me to about 15mph at 3700rpm. I attribute that to the boat just being too small to tote that much weight. I was pleased though. The engine is a GX620 Honda with gutted exhaust and a little carb work. Nothing major.