I'm new to the mud motor world and desperately need some input folks. I just purchased a 1642 Polarcraft with a 25hp Kohler longtail to run the Colorado river in, but I'm afraid I don't have enough engine. I'll be running with three guys and duck hunting gear. The portion of the river that I'll be running is very shallow and rock strewn. So I really need to be able to get this boat on a plane, but I haven't been able to do that on the lake where I'm test running so I'm worried. What speed should I expect to get out of this setup? I don't really care about speed, but I know that's what it's going to take to get this thing up on a plane. Are there any modifications I can make to help get this boat on a plane or am I under powered? Any and all help, suggestions, or input would be greatly appreciated! I can provide more info and maybe a few pic's this evening if that'll help. TIA!!!

Just to put it in perspective my 22hp longtail can get my 1648 on plane at around 10 mph. It only goes 15mph max

It's simple. get a mud motor. shoot ducks in the face.

Check rpms in and out of water.
Measure your prop
Measure your transom
Then report back.


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with three fat asses, dog and gear I am at 15 on plane. that is a 1542 with a 23

With 4 people in that boat dont expect much. That a big load


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Well I got off work too late to get the info that you asked for flint87, but is it safe to check RPM's out of the water?
Sorry bernie255, but it'll be three guys total not four like it sounded.

What could I expect if I were to upgrade to a SWOMP 35? Would it be worth the investment? Sorry to hit you folks with this all at once, but I'm fresh out of time!!!

I would say top speed loaded with the 35 would be somewere around 20


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If the prop you have now is in good shape and the "proper" size for that motor combo it may be worth it to drop a little pitch. I'd consider it for sure if you're planning on running that heavy very often. That's a lot to ask of any motor on that size hull.

Rpms out of water should be north of 4k. That engine can safely turn 4500 oow. Should put you closer to 4k in the water. Your governor needs adjusting.

Rpm is a little low. My 15 is 3800 out of water & 3650 in the water pushing my son & I rite @ 16.3 mph across a calm deep lake. My govener wasn't set rite @ all when I got this motor. It was 3100 in water & 4xxx out of water! Needless to say after abjusting the gov the rite way it gave me about 4 mph & safe rpm range out of water & correct rpm range in water! Couldnt be happier! Try getting the rpm range up where it needs to be 1st man, makes a WORLD of diffrence! Wait did I see it has an 8 inch blade???? Yeah thats a problom for sure too! That should be like a 9x6 or in that ballpark!

yes i measured it at 8", but it sounds like i need a 9X6

Until you fix the rpm issue, prop isn't gonna help, so get that fixed. And a 9x5 might do you better with three guys than the 9x6. Trial and error though with that to get what you like. Some find one works better than the other for them.

The only cheap "mod" I can think of to get you there sooner, is to get up earlier, drink an extra belt of coffee that will have you believing you are moving faster, and enjoy the ride!

OK I got the RPM's adjusted and it planes out pretty easily now. It's pushing two guys about 17 mph. So I'm definitely happy. Thanks for all the input, but I've still got a few questions. First, should a 9X6 prop fit on this 2005 model engine? I ask because when I measure the current prop it appears that a bigger one won't fit. It looks like there won't be enough clearance or very little if there is. Secondly, what's the best boat blind to use with a mud motor? It seems the tiller handle will be in the way of most I've looked at. TIA again!!!

Yes! 9x6 will fit! Make your own custom blind and save $$. Google scissor boat blinds or search here. You can use emt and bimini fittings for one configuration...I get by with heavy schedule pvc but then I don't get cold weather. I get 17.5 mph with two hunters and gear with a 27 LT on a 1648 and that is good enough and I get up early.

These longtails do well with light riveted hulls...a good friend has a vintage Lowe 1648 riveted jon, .072 gauge ('bout 250#), and has an equally vintage 25 HP GoDevil LT. He and his two sons are well over 200# each and the last time they ran, they were hitting 18 mph! I had my GPS so I know. Other than tweaking the throttle to 4400 rpm out of the water, that is the only "mod". I'd gladly trade my 395# 1648 grizzly for a lighter hull.