I recently purchased a 2000 Merc 125HP Classic and was wondering if anyone has any suggestions about which prop I should be running on it. right now it has an aluminum 12.75x21P and it seems to running way too high on the RPM's (5800). I believe it should run no higher than 5250. Any suggestions would be greatly appreciated!!!!

Was thinking that someone that had that motor might respond. I had one a few years back and, if my memory serves me, I ran a 17 and 19P aluminum. Your right about the rpm's at 5200 but it does not make sense that a 21P would be turning so fast. That pitch is at the high end for a 125 I think. What boat do you have it on and what hole is the motor mounted in? I would question if your getting the correct rpm reading and would probably check that out first. Maybe you could tell us how the boat is performing otherwise. ie, speed and holeshot.

That's interesting because I just checked out a Lund Fisherman with a 125. It was sporting a 21 pitch Vengance(sp?). Not sure of the diameter. I was thinking that was alot of prop for a 125, being I run a 17 pitch on my 115 4 srtk. Maybe you're mounted a bit high on the transom. Sorry I don't recall where the one I looked at was mounted, as I was more interested in the prop. We need some more info, like overall performance. Mike

I know on the new engines there is a small plate on it that tells you the dry weight of the engine and min/max rpms of the engine. I am guessing the rpms are fine... You are going to want to stay to the high end of the range they give you or just a hair over it. I would imagine the range is from 5200-6000(guess) DO NOT GO UNDER THIS RANGE. This can cause some serious long term damage to the engine... That does just seem like alot of prop for a 125. I run a 19p tempess on a 175 verado...

I recently purchased a 2000 Merc 125HP Classic and was wondering if anyone has any suggestions about which prop I should be running on it. right now it has an aluminum 12.75x21P and it seems to running way too high on the RPM's (5800). I believe it should run no higher than 5250. Any suggestions would be greatly appreciated!!!!

You did not mention the boat it's on. You definitely have an issue with your tach, the 125 is governed to a max rpm of 5250 - there is no way you could run the 2000 model year at 5800 rpm. Might as well get your tack working right to start with.

21 Pitch on this motor sounds about right. I had the 115 on a 1750 Crestliner Fishhawk that was a draw between a 19 and 21 pitch - but that boat was rigged very heavy with a kicker, and a 36 volt trolling motor and batteries. I ran the 21 pitch, and still bumped the governor from time to time.

Check the wires on your tach, make sure they are all tight, and corrosion free.

I have a 125 on a Warrior 2090BT with a 20p High 5. My RPM's are right at 5200. I know this is the maximum for this motor. I have talked to a couple of mechanics and both confirmed the maximum. I would not take any chances and stay within the limits.

You did not mention the boat it's on. You definitely have an issue with your tach, the 125 is governed to a max rpm of 5250 - there is no way you could run the 2000 model year at 5800 rpm. Might as well get your tack working right to start with.

21 Pitch on this motor sounds about right. I had the 115 on a 1750 Crestliner Fishhawk that was a draw between a 19 and 21 pitch - but that boat was rigged very heavy with a kicker, and a 36 volt trolling motor and batteries. I ran the 21 pitch, and still bumped the governor from time to time.

Check the wires on your tach, make sure they are all tight, and corrosion free.
Burr-
The boat is a Crestliner sportfish 1750. I had the boat checked out by a certified Mercury tech and he said the tach was fine. The boat does have a kicker, 3 batteries mounted in back and a 24v trolling motor on it.
I checked on Merc's site for the proper pitch prop for this motor and it states for overall performance to run a 24P or 26P 4 blade stainless. I had a buddy loan me a 24P and with 3 guys in the boat it was a dog to get out of the hole. But it did run wide open @ 5250rpm & 45 mph. Looks like I may have to sacrifice hole shot for overall performance.