Prop problem?

Hello fellow fishermen. I just bought a 2001 Alumacraft MV Tex special that was a one owner with a 2000 Johnson 50hp (j50plssm). The motor came off a pontoon from a guy with more money then cents because it had a bearing down in the lower unit that was discovered while it was being service so he trades it in on a new Mercury. Its a little cold collared but runs great. My only concern is that when I push the throttle all the way over it will actually cut out but if I back it off just a hair it does it less and it has a sweet spot where it doesn't do it at all. Doesn't matter about the trim. Ive played with it and tried it all the way down and I run it until the front bounces then I trim it down until its smooth. My question is since the motor came off a pontoon could it be red lining and cutting out from having a lower pitch prop? Wouldn't you want a lower pitched prop on a pontoon so it wouldn't bog and would push it with all the people and stuff aboard? Im trying to get the prop off so I can see what pitch is on it but I don't have a prop wrench so Im going to get a socket from work(body shop). Ive only had the boat out 3 times but the last time I run all over the lake thinking it needed to be ran because it had sit for a while but no matter how much I ran it I got the same result. Its got one heck of a hole shot and plains out great and stands on top of the water real pretty but only runs 27mph. The hull only weighs 425 according to specs. I found online so it should at least run 35 or 40. O yeah that was gps speed also from my buddy's phone on the river. No faster no matter up stream or down stream. Same 27 constantly. Any and all input is greatly appreciated as I have OCD about little stuff like this. This is going to wear me out until I figure it out.

You need to find out what RPM's your turning to know if a different pitch prop is needed.

[url=https://www.tinboats.net/forum/viewtopic.php?p=342194#p342194 said:

lckstckn2smknbrls » 18 Feb 2014, 23:39[/url]"]You need to find out what RPM's your turning to know if a different pitch prop is needed.

Click to expand...

That is good advice.


Find your engines "RPM Range" in Owners Manual or at the dealer. Your prop should let your engine run(full throttle) at or near the TOP of this 'range' ...with the boat lightly loaded. As you add passengers or gear, you speed and your RPM will naturally drop...but still in the RPM range. Lots of weight in the boat may require the next size smaller prop to get the engine back up in its "full throttle RPM range". That second prop will make an excellent spare for when you need it.

The engine has a rev limiter built in to the powerpack. It cuts out the ignition when the engine over-speeds. If the engine has the right prop for a pontoon(porch), then it certainly is too small for the MV TEX. The difference in hull speed requires a lot more pitch on your new boat. Try at least 17P. There's probably an 11 or 13 on it now.(a guess)

If your MVTex isn't full of lumber, carpet, and gear...If you generally run light-load and fast(trimmed up)... you might even pull a 19P.(35-39mph). I have set up similar boats at over 40-42mph with a good wind chop and lots of trim. Rarely one comes together needing a 21P. A small tiller boat, with 50-60hp, trimmed up, in a good wind chop, at 45mph, well...you don't sleep through that ride.

Get a good tachometer. Either install a factory tach or use a hand-held diagnostic tach for setting up your prop. Be cautious when buying a prop. If you buy too much pitch, you can't use the prop without over loading the engine. It also makes the boat sluggish out-of-the-hole. If the prop is on the small side, you can always throttle back or use it for heavier loads. No harm there.

My personal boat is like yours. Alumacraft MV1648 with a 40hp(50hp carbs and head) short shaft tiller. I run a 19pitch stainless for light loads. I have a 17P aluminum for pulling grand kids on skis and tubing. The 17 is also used for cruising in unknown waters. It's a lot cheaper if a rock gets a-hold of it.

Hope this helps.

you can use a Tiny tack ,google is your friend, just talk to them and tell what motor you are putting it on and they will fix you up . I think the last one I bought was about $30 or so its been a while . I agree with a base line . establish where you are in rpm now and work from there, any day you're playing in a boat is good !

Well after getting a lot of good info on here I went back to the place I bought the boat from and asked the mechanics about what the boat was doing and they told me it sounded like I needed more pitch on my prop. They suggested I bring the boat by and they would pop the prop off and see what it was. Went by today and they pulled it off. The prop on it was a 11 pitch. I couldn't believe it. I figured it was at least a 13. They put me a brand new 15 pitch solas prop straight out of the box and didn't charge me a penny. If it run 27mph with a 11 I'm wondering how it will run with this 15. I hope I get 35 to 40mph. Hull only weighs 450 so I would think it'll get more but I'm super excited to see what it'll do this Saturday.

Your in the ballpark now! The dealer sounds like a good one to work with.

Listen for the rev limiter to cut in. If you don't hear it you are probably OK. If it is cutting in at top speed, go to a 17pitch.

Really, the best thing is to put a tach on it until you get to the boat dialed right in. After that it's not needed much.

Taking out the boat and trying new props is an excellent way to spend time.


*************