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251 prop help

i have a 98 251 with a 540 ci. i run a 26 pitch bravo at 79.2 mph and 5600 rpm. need a 28 pitch. for the bounce mine did the same thing from 30mph to wot, it sucked so, my buddy and i came up with a solution, we made a wedge out of a certain kind of material (top secret,haha) and put them on the most outer edge of the farthest chim at the back. and it cured it 100%. mine was really bad, the boat would actually jumped out of the water. all my buddies have 253's, 259's, and 270's and they all did it, untill we put these on. and NO believe it or not it did not hurt the top end speed. to be honest it feels like it lifts the rear, and airs the boat out more.please becareful with your dry header set up. you are putting alot of heat in that engine compartment that cant excape. i dont want you to have a fire on your hands. it has happened before. if your interested in what we used let me know and maybe we can hook you up with them for a small price. they will already be cut to size, and the right height.
 
here are some pics of my 540ci. im thinking about selling the boat, do you know anyone that might be interested in it. im in maryland. i know this is off topic but i thought i would ask.
 

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Hey nice 251 !!!! yeah im deff interested in what you have for that cuz im sure at least 2 times the boat did come close to jumping out of the water:eyecrazy: and I look like a tool in 1ft chop when 20ft bow riders are fine and here I am looking like im in 8ft seas haha......... The pipes I run are the gil dry pipes they dont get hot at all it has water jackets to the end of the pipe. no reversion but god damn they are loud !!!!!


as of right now im at 68gps @ 4600 jumping out of the water with a hydro 25p 4 blade that I think sucks and I need to be about 1300 more rpm.
 
yeh i know what you mean along with all my friends. i leave for vacation tomorrow, and when i get back i will take a pic of my boat so you can see what i did. and with the price of the material, cutting it, and shipping it to you (which shouldnt be much, they dont weigh much),your probablly looking at around $40.00. and in my opinon that is pretty cheap to fix a huge problem. let me know what you think.
 
throttletherapy said:
i have a 98 251 with a 540 ci. i run a 26 pitch bravo at 79.2 mph and 5600 rpm. need a 28 pitch. for the bounce mine did the same thing from 30mph to wot, it sucked so, my buddy and i came up with a solution, we made a wedge out of a certain kind of material (top secret,haha) and put them on the most outer edge of the farthest chim at the back. and it cured it 100%. mine was really bad, the boat would actually jumped out of the water. all my buddies have 253's, 259's, and 270's and they all did it, untill we put these on. and NO believe it or not it did not hurt the top end speed. to be honest it feels like it lifts the rear, and airs the boat out more.please becareful with your dry header set up. you are putting alot of heat in that engine compartment that cant excape. i dont want you to have a fire on your hands. it has happened before. if your interested in what we used let me know and maybe we can hook you up with them for a small price. they will already be cut to size, and the right height.
Click to expand...

I don't experience these problems with my 253, I must say I did re-rig engine , transom and steering for other reasons .

Just curious do you have a picture of this wedge attachment. How do you attach them so they withstand the extreme pressure . Is it like the plastic things on the back of a SeaDoo? Do you know something Checkmate doesn't? If so put it out for testing. Altering boats can be dangerous if not all change characteristics and strength limitations are accounted for.
 
no this doesnt look like the sea-doo things, we have done it to 6 other boats and it cured them 100%, and not effecting the performance of the boat at all!!
 
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Their was a post somewhere on this board about running a bead of silicon under the boat and it stopped the porpus
 
24" billet K-planes cured that on mine I had porpus at low speeds around 30 . I have to tuck everything in. Once over about 40 to 45 it goes away I can start freeing it up. Then over 65 I have to start trimming in again. Up near 100 I have the planes planted in pretty far on fair water. The bow rides high naturaly on my 253 I think X-dimension is too low. I am going to try a 2" shorter lower unit then start spacing down if needed. I think it will bring the bow down.
How does you convincor react Big Red?
 
I have porpus bad around 3000-3700 rpms only with trim though. No trim no porpus. My best all around props that I have tried have been bravo's. The pic below I was cruising around 4800 with a bone stock 26p bravo at 1/2 trim.

bowlift.jpg
 
I just put in my new engine and got it running about a month ago. So I was running a bravo 1 30 pitch my RPM was hitting close to 6k so I went to a 34 Lab bravo I turned 5300 rpm I am sure I could of seen 5500 I had a little left. If I need anymore prop I will have to change my gear ratio.I must tell you things happen fast at that speed. You don't want to turn your bravo xr over 5300 to much if you want it to last.

The 26 I will have for sale is from another boat I owned and is one of my personal props. It will not be available until I have things straight with Chris for advertising on this site. I do own a shop. I think my post was removed saying I had one for sale but I also stated it was not available from that post and would be listed in the proper forum at the right Time.
 
Well I get the 25p mirage back in a week or so. Prop shop installed a new hub and cleaned it up. Im gonna give that a try again and see what happens. That was on the boat when I got it. I hope I can get a WOT # to work with. MK I will prob end up taking that prop off your hands. Take your time tho. I wanna try what I listed up top first.

I just cant get over that hydro sucks that bad on my boat. But my fathers 98 22 persuader 454mag runs 73 with it and he loves it.:sick:
 
jammasterj787 said:
what speed at 4800 ?
Click to expand...

Dont know the engine is good for 6000 when I do prop testing I bring a handheld gps. I just really posted the pic so you could see bow lift from a stock 26 prop on a Checkmate. You can not get a baja to do that with a stock bravo in the same size class
 
A Mirage prop is not the right prop for your boat with the horse power you have.
I ran them back in the early 90's. Slippage factor is high and handling is sacrificed, They slip worse in turns. Sent a few in had a cup put into them to make them hook up better. Still no comparison to a bravo 4-blade. Might explain some of your ill handing characteristics of your convincor and why you started adding stuff to the bottom of your boat.
 
26 pitch bravo1 prop at 4800 RPM about 70 that's what my covincor did when I first got it 6-years ago. It had a hp 500 blue engine and I ran a 26 bravo 1 could never turn it past 4800. I didn't have a GPS speedo then, So it was off one way or another. But I will tell you it ran hard it bent the bennett trim tabs that came on the boat.
 
mkhammer said:
A Mirage prop is not the right prop for your boat with the horse power you have.
I ran them back in the early 90's. Slippage factor is high and handling is sacrificed, They slip worse in turns. Sent a few in had a cup put into them to make them hook up better. Still no comparison to a bravo 4-blade. Might explain some of your ill handing characteristics of your convincor and why you started adding stuff to the bottom of your boat.
Click to expand...




I have not added anything to the bottom of my boat????? only a water pick up. :confused:
 
throttletherapy said:
i have a 98 251 with a 540 ci. i run a 26 pitch bravo at 79.2 mph and 5600 rpm. need a 28 pitch. for the bounce mine did the same thing from 30mph to wot, it sucked so, my buddy and i came up with a solution, we made a wedge out of a certain kind of material (top secret,haha) and put them on the most outer edge of the farthest chim at the back. and it cured it 100%. mine was really bad, the boat would actually jumped out of the water. all my buddies have 253's, 259's, and 270's and they all did it, untill we put these on. and NO believe it or not it did not hurt the top end speed. to be honest it feels like it lifts the rear, and airs the boat out more.please becareful with your dry header set up. you are putting alot of heat in that engine compartment that cant excape. i dont want you to have a fire on your hands. it has happened before. if your interested in what we used let me know and maybe we can hook you up with them for a small price. they will already be cut to size, and the right height.
Click to expand...

The post above about adding stuff to the bottom came from THROTTLE THERAPY

mkhammer said:
why you started adding stuff to the bottom of your boat.
Click to expand...
 
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