I bought my motor used with a wore down prop but would turn 4000 rpm.Just put on new prop and am getting 3750. Are my rpms low or about right for a new prop?

When my PD was stock with a new prop, my best speeds came around 3850, so depending on what type of boat you are running, you sound about right.

seems a little low to me...what boat you runnin it on and what kinda load did you have in it gettin those numbers?

My PD has always turned a good prop around 4000 rpms. Anywhere between 3950-4050, depending on conditions. I set tiller for comfortable tiller torque or lack of, and its usually turning around 4000.

did speeds increase????

i have a worn stock prop that will turn 4300 and bump the rev and not go over 19 mph

i have a slightly used prop that will run 25 at 4050

if your rpm drop at the same trim position you are getting less prop slip. If your rpms are lower ans less speed you might just have a prop with more pitch than the motor/boat combo can run with you caditions.

Rpm on trailer is 42and some change.Motor is on a 18x38 GoDevil boat . I think the problem is because of the skinny boat lettin the arse ride low but not sure.Im nearly maxed out on trim.Not sure if this is all I can get out of it.I know a little wider boat will ride higher and probably run faster but this round chine skinny boat sure does well in bad stuff.

I've got a question on this also. I got a new PD 36 last summer and used it duck hunting for the first time this winter. For the first half of the season I think I was running in the high 20's with me (and I'm fat), my youngest son and a buddy of his with all the gear. A couple of times I had 4 in the boat, and I think I was still running in the low to mid 20's. After that I had some engine issues, but after I took care of them I was running 1/2 to 60% of the speed I had been running at the same rpm's (seems like I was running best at 3950 - 4050 rpm).

I'm trying to figure out what the deal is and finally called K.P. He thought if I was running at the same rpm but going slower that it must be a prop issue: either I had worn the prop down too much (I have since measured and I haven't) or I had scarred the blades on my prop. At this point I remembered going over a gravel road several times with the collar down where the motor wouldn't kick up). I look at the blade edges and they are scarred but I wouldn't have thought it was bad enough to make this much difference. Have any of you experienced this or have an oppinion as to cause and what I need to do?

What were the engine isssues and what did you do to fix them?

You said you have the PD on a GD boat. Is the bottom of the transom on the the boat cut at an angle? If it is, then your motor is likely running way too deep. Since you bought the motor second hand, you wouldn't have gotten the ear full from Peck or KP about the transom. A buddy of mine is running a short shaft PD on a 20" transom because the transom is cut in the bottom. Works kinda like a jack plate, you gotta bring the engine way up to get it out of the water with a cut transom.

I dont know much about this whole mudmotor gig but putting a short shaft motor on a tall transom boat where you cant reach as deep in the mud just dont sound like a good tradeoff to me.

THat's why Peck gave him such a hard time about it when he did it. Hasn't caused any problems. With the cut transom, the boat sits deeper in the back. Burch wouldn't have had that conversation with the PD guys because he bought his unit second hand. A long shaft with a cut transom would put the prop way down in the water, which could definitely be costing him plenty RPM's.