I run a gx690 on a backwater swomp (1548 weldbilt) and am wondering who else running similar power has mixed it up with the props. changed it during duck season to better cary load, and then a different in the summer to pick up a little speed?

I run a GX620 on the same hull. I settled on a 9x4 for my setup. runs pretty well in all condition and hauls a load very well for only 20hp. I'd start with a 9x5 for that rig... Shoot for solo RPM in the water between 4000-4200. This way when you load it, you'll be in the 3800 range and it wont be a slug.

I'm bout to start messing around with prop pitch on my kohler 25 GDLT. Got my governor adjusted to turn it at 4200 oow. Kinda slow with a 9x5 @ 16 mph but going to try a 9x6 and a 9x7 to see where I'm at for summer time unloaded speed and probly keep the 9x5 for duck season.
The 690 is 22 hp? and you've got a light boat. Might be able to turn even more pitch unloaded.
What speeds are you getting now?


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That graph shows a pretty steep climb up to 22hp. Unless it just won't go past 3600rpm or it falls off completely after that rpm, I'd say it's got a few hp left.

What prop are you currently running?


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I have a gx670. It says 24hp on the front of the motor.

Yeah, you have to do some testing. My 27 MB LT is rated for the 9x7 but I do much better with a 9x6. Like you, Flint, I need a few more horses- most likely the 35 Swomp SS- to run two hunters and gear in the low 20's. That will happen in a year or two.

I have the gx670 on a backwater frame and I run a 9X6 backwater on a 1448. Seeme OK with 2 guys and hunting load for that boat (which was overloaded for a 1448, but that's for another day). By myself she was running on the gov. at about 3/4 throttle. With a longer boat and your added displacement of the gx690 it should work well and not lug the motor too much. Good luck and enjoy!

We ran a 9x6 and a 9x7 (both mb props). The 6 never left us stranded, the 7 didn't seem to get us quite as far. Hard to say for sure because we never put them through testing same day. When one wore out we replaced. Never ran speeds, but the 7 would've edged it out.

9x5 = 16 mph no matter what.
9x6 = all deep water testing
16 mph in a hell of a current upstream.
21 mph down stream.
Still can't figure out what's wrong with dumbass tiny tach. ImageUploadedByTapatalk1425081284.931802.jpg
Jumped a beaver dam today to.
Tried to go back and do it again damn near killing myself.
Gona try to upload vids to YouTube.


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