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Longtail speed help
https://www.mudmotortalk.com/mmt_v2/viewtopic.php?f=6&t=62393		 Page 1 of 1
Author:  Waterspaniel7 [ Thu Jun 25, 2015 12:16 pm ]
Post subject:  Longtail speed help
I have a 1452 riveted flat jonboat that I just mounted a gx670 beavertail long tail to. Full disclosure, this is my first mud motor and I have perished some other similar strings. I'm only getting about 10mph solo and about the same with a 200lb friend seated in the center in the boat. This is my first post and have two questions for you guys: 1) how can I get more prop contact at low speed? Right now I have to pull up hard on the stick to get the prop to dig In. Even more so when in a turn. Maybe this is par for the course but I'd like to know either way.

2). How can I improve my speed? I'd like to keep my hull if possible because I've spent a ton of time and sentiment on it but am open to future hull set up suggestions.

Thanks in advance.
Author:  Bigbend [ Thu Jun 25, 2015 1:29 pm ]
Post subject:  Re: Longtail speed help
Whats your transom height? At full throttle does the prop want to pop out, or only at slower speeds? Measure your prop diameter, is it worn?

I would check your RPM's too. Every used longtail i have bought came with a jacked/busted throttle that needed attention.

That is a wide boat for a longtail, but engine is a 24HP right? should get more than 10 mph.
Author:  Russ [ Thu Jun 25, 2015 1:34 pm ]
Post subject:  Re: Longtail speed help
That boat with that motor should easily hit 17-18, if not 20. It's got enough lift that 10mph isn't even close to what it's capable of.
Author:  Waterspaniel7 [ Thu Jun 25, 2015 2:54 pm ]
Post subject:  Re: Longtail speed help
Not sure about the prop size but will measure and let yall know. It has a 16" transom and yes it is a 24hp. The prop doesn't appear worn out nor does it jump at full throttle. It looks to be riding with the cavitation plate right above the water line if not barely in it. It also feels like the prop is catching and pushing the boat forward only to rock back and it's slows down. Ideas?
Author:  Davo [ Thu Jun 25, 2015 3:10 pm ]
Post subject:  Re: Longtail speed help
Your cavitation plate is at the right level, so if the prop is 9" from tip to tip it sounds like the cup or pitch in the prop is not right. Is the prop new? If you run sand or hard mud and put the prop in a bind it will throw off the cup/pitch. If the prop is new, you will need to put a tach on the motor to check the rpms.

I used to run a 18hp mud buddy longtail and could get around 17-18mph out of it.
Author:  Waterspaniel7 [ Thu Jun 25, 2015 5:22 pm ]
Post subject:  Re: Longtail speed help
The prop is 9" and doesn't appear worn. I tried to attach a picture of the prop but don't know if you can tell much from it
Author:  kibb [ Thu Jun 25, 2015 7:16 pm ]
Post subject:  Longtail speed help
The cavitation plate needs to be riding at least an inch or so under the water. The only time it should be out if if you force the tiller down and pop it out to surface drive it in the shallow stuff. Start by bending the back end of the cavitation plate in 1/8-"1/4" increments and testing until you get it right.

If you have a tach, adjust your rpms to run around 3500 in the water.
Author:  Glades Ranger [ Fri Jun 26, 2015 6:03 am ]
Post subject:  Re: Longtail speed help
I agree with Russ and the other posts. Your 1542 riveted hull with that 24 Honda can go much better. With the tach out of water rpms around 4200-4300. Let us know how it goes! Weight distribution is an important factor too; relocating battery and/or gas tank to the front might improve planing. I recommend steelflex or Gatorglide for the hull bottom. If the carb air filter has a precleaner, get rid of it, will breathe better. Go with synthetic oil and grease.
Author:  Bigbend [ Fri Jun 26, 2015 9:05 am ]
Post subject:  Re: Longtail speed help
Author:  Waterspaniel7 [ Fri Jun 26, 2015 10:29 am ]
Post subject:  Re: Longtail speed help
Thanks for all of the good tips. I think I found a solution to the problem I have had getting the prop in the water when I'm going slow. Hopefully this will free up my top end speed with a better angle. The picture below shows a nut you can adjust to change the pitch of the shaft. I don't know how I didn't see this before but oh well. I am going to make some adjustments and see how it works this weekend. Big Bend mentioned an air filter solution for more power. Are you referring to the black filter at the top of the box? See pic below.
Author:  Bigbend [ Fri Jun 26, 2015 10:53 am ]
Post subject:  Re: Longtail speed help
Bet that makes a big difference. I think GR was saying to pull the black spongy pre air cleaner from your filter. It keeps dust out of the filter but not really needed in this application. Definitely leave the actual air filter in there though (the white one). Make sure to post up new speeds. Bet you at least get 17.
Author:  Waterspaniel7 [ Fri Jul 03, 2015 3:18 pm ]
Post subject:  Re: Longtail speed help
I finally had a chance to get out and test the changes to the pitch of the tail's angle made by simply cranking the knob under the mount. The boat is now running closer to 14 mph (with me @175lbs and my friend sitting in the middle @200lbs). I won't win any races but the speed is sufficient for what I want to do and the handling is much better. I say the handling is better because before I adjusted it I wasn't able to get the prop to dig in at a sharp turn because the pitch of the tail was too high. I also removed the pre-filter. Just installed a tach this afternoon (the brand suggested). The installation took 5-10 mins with only a pair of needle nose pliers to cut the excess wire and zip tie. I will post the rpm's once I hit the water again. Hopefully this weekend. Thanks for all the help guys.
Author:  SETx Longtail [ Fri Jul 03, 2015 6:51 pm ]
Post subject:  Re: Longtail speed help
That looks like a bottom stop and not really for "trim" you should set that to whatever you want your maximum depth to be if you were to have to dig out of something. Your cavitation plate should be bent to achieve the proper prop depth in the water and adjusted as needed.

Also, on your Honda. Don't be scared to turn it 44-4500. I saw my best speeds and load carrying when I dropped pitch so I was turning about 4100 solo and 38-3900 loaded. Remove the air filter all together and gut the exhaust. How dusty was the last River you ran on? My 20hp Honda on a beat up 1548 Weldbilt was seeing 20mph every now and again. No reason you shouldn't see equally good speed. Those Honda engines are built much better than a Briggs and will turn more RPM than you are comfortable giving it I'm sure. The cart racing world turns those engines well past 5K on a routine basis.
Author:  Glades Ranger [ Fri Jul 03, 2015 7:47 pm ]
Post subject:  Re: Longtail speed help
Not saying your Honda 24 has this problem, but my friend's last motor was a Honda 24 MB LT. The electronic fuel pump that it came equipped with was not providing the correct fuel flow rate so it bogged down periodically and did not run as it should have. You did not state the RPM's you have at idle and wide open. I think SETxLongtail is exactly right about the upper setting. I have set both of my last two Kohler 25's and my present 27 at this range without any damage to the motor. As was said, prop wear can really affect the performance- sometimes the recommended size prop might not be the right fit for your situation, for example my 27 is rated by most LT mfg.'s for the 9x7 but I run 1-2- mph better with a 9x6. This you find by trial and error, I would advise a new backup prop in any case- better to be ready at all times for duck season. :mrgreen:
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