Hey y'all, new member. I had my motor serviced by sportsman's in abbeville (new prop, change oil, plugs) and today was the first time I ran it since then.

Today, at WOT, it would not go over 3200 rpm's (in the past it could go above 3500, typically run it at 3300)



Do y'all know of any possible causes to this?

It was also stalling out at one point; I think that could be attributed to bad gas though.

Could that be the cause?

Did the old prop have a lot of wear? Is the new prop the same pitch as the old one? Does the boat show a significant speed difference between the old prop at 3500 and the new prop at 3200? What is your max rpm with the prop out of the water?

It normally is fast, for a LT. It being on a very light hull is the biggest reason why I think.

It most likely won't be until the weekend until I can mess w/ it again.

Whats a good rpm to run these motors at? I seldom run it at 3500, usually 3300 at most, but if doesn't hurt any, I may have to change that.

What kind of boat are you running?

Let me know what you get tomorrow. Try positioning your tank and what ever else heavy items your carring around in your boat.

I ran mine today. 17 mph @ 3400 RPMs. Tomorrow I will be out again, but with with an extra person and alot of fishing gear.

I went today. I weigh 170 or so, battery and 2 gallons of gas.

4010 rpms oow and best I'd get was 3300 in the water at wot. Between 19 and 21 mph avg.

It's gotta be the new prop. That speed is fine but add my gear dog, person etc, in not gonna get those rpms. In the past, w/ a load, could go over 3500 in the water.

Im going to put the old prop back on.

Could it be the new grease?

I'm going to take some pics of the props and post it up

Those are some nice speed numbers.

I completely forgot to get my GPS out and get a speed reading today. Engine ran pretty good other than it wants to bog down and shut off every time you hit the throttle from idle.


I would put the old prop back on and see what happens, then you will really know if it is the prop that's the problem.

here are the pictures of the props. kind of hard to capture the comparison, but the new one seems much bigger.

It shouldnt. From my thread on "running lean" CB stated that if I can run 4000RPMs out of the water I should be able to do that in the water and I agree with him, but once under load prop pitch is gonna have alot to do with getting to that higher RPM.

Your new prop seems to have a lot of cup to it.

Im by no means and expert on Mud motors. Maybe one of the guru's can chime in and help you out.

Ok, gotch ya

is this a pretty common thing? My kohler is similar. i have 25hp kohler and it runs 4050rpms but is around 3000-3200rpm in the water. i have a 9x6 also. brand new

Update: overall, speeds are the same, just running at less rpms and after getting the bad gas out of there, no more issues.

Last sat, About 17 mph avg w/ me (170# or so) lab (75#) friend (at least 215#) spare 3 gallons gas and hunting gear (was minimal for teal). That's going back up the calumet.

changing the prop on my boat can make a dramatic difference. I have a 27hp lontail and initially was running an old worn down 9x7 prop and completely empty was hitting 3900 RPM. I changed to a 9x6 to get more speed and my RPM suddenly went down to 3500. over the past 3-4 months as the prop wore down it slowly headed back up and is now up to around 3850 rpm. At least on my rig I noticed the RPM and performance seemed to be more affected by the thickness of the leading edge of the prop rather than the total size. Before I was loosing diameter, I was still getting increased RPM just as the leading edge wore down. So even if you do not see a significant size difference in the diameter of your proprs, the thinner edge of a slightly worn prop can still make a difference. I would run the rig for a while and see if you pick up performance as the prop wears in.
I agree with others that changing the governor is not going to affect the in water performance. My understanding of the governor is that it prevents damage to the engine from over-reving when the prop pops out of the water and your RPM's shoot up when the load on the prop suddenly decreases.

didn't realize it was you till I saw the boat pics in the other thread. The new prop has more surface area and more cup, which is making the motor push more water. The motor is pushing all it can, meaning you are currently 'overpropped' just a hair. Your rpms will come up as the prop wears out. A 9x5 will perform better on that hull if you really load the boat, say 3 guys and dog and gear. The 14 foot length isn't ideal for getting a load on plane with that 23, so the lower pitch will help when you've got a heavy load.

The 23 sits on the bubble between a 9x6 and 9x5 prop. 9x6 is for lighter loads, which your boat is with just you and another person in it.

You thinking about upgrading boats?

I didn't realize my old prop was that worn...these long tails are sensitive creatures.

I'm getting the middle bench removed, support added in its place, extending the front deck a scoach and add aluminum floor

Post up some before and after pictures!