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2003 Persuader 218 Prop Issue

giffo13

giffo13

New member
I have a 2003 218 Persuader with a 350 mag mpi and a bravo one. The boat porpoises like crazy from 25-45mph. I am running a 24 pitch 4 blade bravo. I think I have room for a few hundred more rpms. should I get it reworked to a 22pitch? Suggestions?
 
Have you paid to have a prop reworked before? Do you have someone who does good work for cheap? I think I would just borrow or buy a second prop in the lower pitch to try out or have as a spare.

But I don't think a prop change is going to help as much as you hope it will, with just a prop change most likely you will still have much more porpoising then you want. If you can't get rid of it with Trim on the leg then, installing tabs are your best answer.
 
@karzrus I forgot to add I also have tabs. My trim is all the way down with tabs 3/4 the way down to keep it from porpoising while cruising. As soon as I get over 45mph I can pull the tabs all the way up and trim way up without any porpoise. It just doesnt make much sense to me.
 
I had a 219 Peruader with 350 mag and alpha with no tabs. It had the porpoise issue with a 3 blade Mirage but a 22 Bravo 1 fixed that problem for me. I think you are probably a bit over pitched with a 24 on that setup. Don’t know that change in Pitch will fix porpise though. I’d figure out where tabs are set at even with bottom of your hull for reference on indicators. Try running with trim slightly up and tabs up all the way and tab down slightly past neutral to control porpise. If you’re running with tabs down 3/4 of the way it sounds too far to me. Agree with trying a different prop before working the one you have. Good luck.
 
giffo13 said:
@karzrus I forgot to add I also have tabs. My trim is all the way down with tabs 3/4 the way down to keep it from porpoising while cruising. As soon as I get over 45mph I can pull the tabs all the way up and trim way up without any porpoise. It just doesnt make much sense to me.
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Lots of weight in the back for the length of the boat, means the CG could be a bit far aft. A rocker at the back of the hull will make it worse and a hook better. Just for interest, try and get one passenger to move all the way forward to the front of the bow (if you have a bowrider) or if you have a cuddy and can get a person as far forward as possible in the cuddy, try it and see how much you can raise the tabs at cruise before it happens. If it gone, then you can try to put less weight up front and even try to possibly move the anchor and battery to the front. If it still porpoises with a person up front, then it would take a lot of weight to change the CG. Hopefully it would help a lot. I have a 2400 Pulsare / 300R and I have to run it at full negative trim (no tabs on the boat) and it will not porpoise. After about 40 mph I can start to add trim and after about 50 mph I can trim as much as I want. If I put 2 people in the back seat, it wants to porpoise if I hit a small wave and it will stop eventually but then I lower the jack plate at full negative trim and that takes care of it at 28 mph cruise. So I really do not have the issue but with more people in the back (CG moves back) I can just get away with it.
 
@karzrus I can feel the CG is way off and Ive only had a couple people up front when the cockpit is full. Ive been told that going to a lower pitch would help tremendously. The reason being because the 24 pitch is creating so much pressure trying to spin that it will make a small boat porpoise. Not sure how true that is but we will find out. Im planning on getting my current prop reworked to a 22 and we will see how that goes. Thank you
 
giffo13 said:
@karzrus I can feel the CG is way off and Ive only had a couple people up front when the cockpit is full. Ive been told that going to a lower pitch would help tremendously. The reason being because the 24 pitch is creating so much pressure trying to spin that it will make a small boat porpoise. Not sure how true that is but we will find out. Im planning on getting my current prop reworked to a 22 and we will see how that goes. Thank you
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I have a 218. 24 4blade Turbo. No trim until about 40mph. They don't need any trim at slow speeds and will porpoise if you do, maybe just a tad if you work the throttle. This is true for most Checkmate models. Everyone wants to trim them but remember this isn't your neighbor's Crownline. WOT you can trim it all the way out until you lose speed.

-Craig
 
@Craig Good advice, thank you. I just assumed it was bad to be trimmed all the way down once you are on plane. If it isnt hurting anything I guess thats what I will do. And you are right about WOT. It runs best with tabs up and trim up until I lose speed. Doing this in my old searay I would be porpoising like crazy!
 
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