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| Excel hull slapping http://mudmotortalk.com/mmt_v2/viewtopic.php?f=4&t=72477 |
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| Author: | lj45225 [ Thu May 17, 2018 4:35 pm ] |
| Post subject: | Excel hull slapping |
I have a 1754 f86 with a 2012 35 gtr that I've had since 25hrs (has 212 now). I knew upon buying the boat that I was going to need to do some engine work to push this boat right. With the motor stock I was getting about 23-24mph at about 3900 rpm in deep water with 12x10 GT 2 blade. Well after installing PVT cam, push rods, Billet rods and piston, stainless valves shims, roller rockers, all that nonsense, the boat started Hull slapping bad at the same speed,rpm, pin position ect. I can move it to the 3rd hole down and it doesn't hull slap, but then I run out of trim and the prop is buried. OOW rpms cut out at 4650. Why the hell it is it Hull slapping so bad at such a low speed after the mods? Btw, I put on a burnt up prop and it it got it up to about 4400rpm. I know my Governor Not letting the prop turn up, but that's a different issue. |
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| Author: | Quack N Stack [ Thu May 17, 2018 4:46 pm ] |
| Post subject: | Re: Excel hull slapping |
What do you mean by “slapping”? Move some weight around in the boat, try different weight in different places Get some 4800 coils, they arnt very expensive and give you more rpm range Trying running a heavier pitch prop. The hammer prop would probably be a good place to start |
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| Author: | lj45225 [ Thu May 17, 2018 4:52 pm ] |
| Post subject: | Re: Excel hull slapping |
Porpoising, just like it will do in an outboard at full speed... But it starts at 23-24mph. And it didn't do it before the mods, what would make it do it now? And I have 10gal and 2 batteries under the front deck. |
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| Author: | Quack N Stack [ Thu May 17, 2018 5:39 pm ] |
| Post subject: | Re: Excel hull slapping |
I can’t think of anything motor wise that would make it do that, other than going faster. But if it’s happening at the same speed that it wasn’t before than I couldn’t tell ya I really don’t know. I’ve seen people put a weld at the back of the boat that runs parallel with the transom that acts as a trim tab. Stops the porpoiseing |
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| Author: | lj45225 [ Thu May 17, 2018 5:49 pm ] |
| Post subject: | Re: Excel hull slapping |
| Author: | Wchauvin [ Thu May 17, 2018 6:32 pm ] |
| Post subject: | Re: Excel hull slapping |
Had similar issues. Had a built in gas tank added to the front and a storage box in the front. That extra weight up there helped a lot. Get you some mechanical trim tabs for about 60 bucks too and that will solve it completely for you bro |
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| Author: | lj45225 [ Thu May 17, 2018 6:38 pm ] |
| Post subject: | Re: Excel hull slapping |
| Author: | Wchauvin [ Thu May 17, 2018 6:56 pm ] |
| Post subject: | Re: Excel hull slapping |
They make some that are only about an inch long bro, that's all you will need, trust me. I have some on my crawfish skiff that is run through cypress trees all the time and never had an issue with them. For under 100 bucks, you can't go wrong in trying it |
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| Author: | lj45225 [ Thu May 17, 2018 7:05 pm ] |
| Post subject: | Re: Excel hull slapping |
| Author: | Wchauvin [ Thu May 17, 2018 7:17 pm ] |
| Post subject: | Re: Excel hull slapping |
Mine are, but you can get some that are bolted on bro |
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| Author: | lj45225 [ Thu May 17, 2018 7:29 pm ] |
| Post subject: | Re: Excel hull slapping |
| Author: | flint87 [ Thu May 17, 2018 7:59 pm ] |
| Post subject: | Re: Excel hull slapping |
| Author: | lj45225 [ Thu May 17, 2018 8:09 pm ] |
| Post subject: | Re: Excel hull slapping |
| Author: | Wchauvin [ Thu May 17, 2018 8:49 pm ] |
| Post subject: | Re: Excel hull slapping |
Get them tabs bro, you need them and you won't regret getting them |
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| Author: | Russ [ Fri May 18, 2018 5:32 am ] |
| Post subject: | Re: Excel hull slapping |
I was porposisong at 32-33 solo with throttle left. Got a prop worked, he played with the rake to get more stern lift and added a bit of cup, now it doesn't porpoise until 36 (which I'm rarely solo nor run max throttle). #CFFITR #TheGhostBoat #whoneedsphysicsihaveamudmotor |
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| Author: | 50fps [ Fri May 18, 2018 7:25 am ] |
| Post subject: | Re: Excel hull slapping |
| Author: | lj45225 [ Fri May 18, 2018 7:48 am ] |
| Post subject: | Re: Excel hull slapping |
| Author: | Russ [ Fri May 18, 2018 8:29 am ] |
| Post subject: | Re: Excel hull slapping |
So, for some clarity, proposing isn't just a function of speed. That's only part of the equation. Thrust angle, the amount of thrust the prop attempts to provide (because it has more nuts), boat angle in relation to the lift and direction of travel all play a factor. Your prop having more power at it without the water lugging it down may not produce more rpms before you start porposing simply because of how it's trying to shove the boat vs before. Solve the porpoising, you'll get more rpms because you have more power. Yes, changing weight distribution, prop rake/cup/pitch, etc will have more immediate and noticeable effects, but having more power at the prop can and apparently did change enough to cause the current issue. Trim tabs, load change, or effective prop rake/cup should solve your problem. Add another guy in the back of the boat with you and see if you don't pick up speed and/or at least solve the bounce. #CFFITR #TheGhostBoat #whoneedsphysicsihaveamudmotor |
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| Author: | lj45225 [ Fri May 18, 2018 8:42 am ] |
| Post subject: | Re: Excel hull slapping |
| Author: | cb5331 [ Fri May 18, 2018 11:04 am ] |
| Post subject: | Re: Excel hull slapping |
| Author: | Russ [ Fri May 18, 2018 1:33 pm ] |
| Post subject: | Re: Excel hull slapping |
Hash tag The Ghost Boat FTW #CFFITR #TheGhostBoat #whoneedsphysicsihaveamudmotor |
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| Author: | lj45225 [ Fri May 18, 2018 1:34 pm ] |
| Post subject: | Re: Excel hull slapping |
One 40 lb bag on the deck made it stop Hull slapping.. got it up to bumping 25mph at 4050rpm in deep water. If I trimmed up any higher the prop would lose water. That's with trim pin on the 2nd hole from top.. I would just think that this 10x12 would be running up in the RPMs more. So it got me to looking and I saw that the table that sits on the idle screw is not throwing to the wide open position. I'll try to attach a picture |
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| Author: | Swampin [ Mon Jun 11, 2018 7:00 am ] |
| Post subject: | Re: Excel hull slapping |
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