I just got a Mud Buddy 25 hp Kohler long tail motor to put on my 1542 express all welded jon boat. I took it out today for the first time and was a little disappointed in the performance. With just me in the boat, I felt like I was only going around 10 mph and was having trouble planing out.
I was expecting to run in the 20 mph range.
A few things I noticed:
RPM's were around 3800 at full throttle
prop measures 8" diameter but unsure of the pitch.
The cav plate seemed to be riding pretty far under the water.

Any suggestions as to why it did not go any faster/perform better?
I have a 9x7 prop also. Should I try it?
Thanks for the help.

Yes on changing the prop to 9x7 adjust cav. Plate and it's a long tail ====no speed demon

that 8 inch prop is garbage. put the other one on IF it measures 9 inches and isn't worn down as well.

definitly a prop issue, not to many things to diagnose with a long tail

X4 on the prop

Where should I start on adjusting the cav plate?

flare the end of it up a lil, it don't take much you can adjust it towhere you need it, it should ride just under the surface

Ok, I did read that if it is running too deep, to bend it down. Is that true?

Yes bend it down to move th propl closer to the surface and up to make the prop ride deeper

Change the prop before you start adjusting the cavitation plate. Sometimes they act differently with different props.

I have the same motor on a 1546 xpress and get the same speed as you. I'd like to know what prop you go with and how much it helps out.

Is it the right transom height/motor combo?

Almost perfect.

Ok so what RPM's are you guys runnimg these up to? My buddy has a Kohler 25 just like mine on a Go Devil frame and we took the boats out the other day his was running wide open at about 4600. I bumped mine up to 4200 and got a good increase in speed it seemed like, but what RPM should it be at wide open?

He may spin it up to 4600 out of water, but I call B.S. on in the water.

With the 9x7 you should be somewhere in the 3800-4000 range empty.

I agree. The governor kicks in at 4100 according to Coco. The prop is your problem. A 9x6 or 9x7 just depends on how much weight your going to pulling. I used to get 19 on a gd 24hp with a 9x7 in the summer fishing with light loads. The 6 is a little slower but you'll be able to get out of the whole faster with it loaded down. But still will do 15 or more depending on water conditions