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usherjs
MMT Member
Joined: Sat Apr 28, 2012 8:21 pm Posts: 8
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 Performance problem - 18x48 w/ 37EFI
I have a new 1848 custom made duck boat with a new MudBuddy 37EFI HDR. By all accounts, the boat should be able to hit 30mph with a moderate load but the best I can do is 25mph. It gets up on plane easily and turns 4500 RPM with no problem. As I trim the prop lower into the water, the best speed I can attain is 25mph but the RPMs never get below 4350. Any thoughts on why this is? Should I consider more prop? Say, the Hammer? Or, maybe change the belt ratio?
BTW, I have a 21 inch transom and ordered the tall transom configuration of the HDR. Any way to verify that I have the right model?
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Sat May 21, 2016 5:13 pm |
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JD145
MMT 1000 Club
Joined: Wed Jun 04, 2014 9:01 pm Posts: 1289 Location: SWGA
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 Re: Performance problem - 18x48 w/ 37EFI
Tall transom should have 8 bolts in the clutch cover. What about your current prop? Is it worn bad? Could be part of your issue.
_________________ 1854 Prodigy DPE Level 3 HDR
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Sat May 21, 2016 7:17 pm |
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JD145
MMT 1000 Club
Joined: Wed Jun 04, 2014 9:01 pm Posts: 1289 Location: SWGA
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 Re: Performance problem - 18x48 w/ 37EFI
In my experience the hammer doesn't gain you speed. Is it a heavy boat? Open or full of boxes?
_________________ 1854 Prodigy DPE Level 3 HDR
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Sat May 21, 2016 7:24 pm |
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VooDoo Daddy
MMT 1000 Club
Joined: Sun Mar 17, 2013 6:55 pm Posts: 2005
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 Re: Performance problem - 18x48 w/ 37EFI
I am having the same problem, my boat has recorded 31 before, always did about 30. I noticed last year that I cannot get it past 26. Boat Dr is looking at it now. Could be prop, could be governor spring, could be valves, could be one of about 6 or 7 things probably.
_________________ VooDoo--what you get when you leave your Voo outside all night long.
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Sun May 22, 2016 9:18 am |
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usherjs
MMT Member
Joined: Sat Apr 28, 2012 8:21 pm Posts: 8
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 Re: Performance problem - 18x48 w/ 37EFI
Thanks. I do have eight bolts in the clutch housing cover so I'm good there. And, the prop (as well as the entire rig) is new so that's not a factor. As for the boat, it is mostly open but the style of construction probably makes it a little heavier than a GatorTrax of similar size and shape -- but not that much. I did have two kids (125 & 50lbs), a dog, and a six gallon gas (in addition to the 10 gallon built-in tank) near mid-boat just to simulate a near hunting load.
I would figure that if the engine weren't running well, I wouldn't be able to keep 4300+ RPM. Is that right?
And I was thinking if slippage was the issue with the big blade, then maybe a hammer would grab more water. Sounds as if you don't agree. What is the benefit of the hammer blade then?
Any other thoughts come to mind?
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Sun May 22, 2016 2:02 pm |
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JD145
MMT 1000 Club
Joined: Wed Jun 04, 2014 9:01 pm Posts: 1289 Location: SWGA
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 Re: Performance problem - 18x48 w/ 37EFI
Hammer will step a load quicker and just handle a big load better. If you're talking top end speed the big blade will be the one that provides the most out of the two. Im not sure a stock 37 can sufficiently spin a hammer either. Maybe try shifting the weight around in the boat, different boat/motor combos like different things. I doubt its your valves because it sounds like your RPM are good. Im also not sure should necessarily expect a steady 30 mph with a stock motor but you definitely have some speed left on the table.
_________________ 1854 Prodigy DPE Level 3 HDR
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Sun May 22, 2016 2:42 pm |
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bdavis85
MMT Pro Member
Joined: Tue Jan 31, 2012 7:48 am Posts: 147
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 Re: Performance problem - 18x48 w/ 37EFI
i have an 1848 prodigy with a 35 gtr and can only hit 26.5. I have even decked the heads and gutted the exhaust.
_________________ 1848 Prodigy with stage 1 35 GTR BPS Pro Staff
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Mon May 23, 2016 11:53 am |
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TPerkins
MMT 1000 Club
Joined: Wed Jan 02, 2013 12:59 pm Posts: 1793 Location: Clear Lake, Tx
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 Re: Performance problem - 18x48 w/ 37EFI
That sucks, im assuming its a loaded out boat?
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Mon May 23, 2016 2:26 pm |
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Matt Boyt
MMT Member
Joined: Sun Jan 10, 2016 2:45 pm Posts: 10
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 Re: Performance problem - 18x48 w/ 37EFI
1854 prodigy 4400 HDR runs 30 all day with 2 people
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Mon May 23, 2016 7:10 pm |
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krazo
MMT Addict
Joined: Thu Sep 06, 2012 8:44 pm Posts: 667 Location: SE Bama
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 Re: Performance problem - 18x48 w/ 37EFI
_________________ 1754 prodigy- stage 2 GTR
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Tue May 24, 2016 8:47 pm |
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txmudcutter
MMT 1000 Club
Joined: Mon Jan 30, 2012 9:08 am Posts: 2307 Location: Nederland, TX (SETX)
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 Re: Performance problem - 18x48 w/ 37EFI
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Wed May 25, 2016 5:30 am |
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dead animal
MMT 1000 Club
Joined: Fri Jan 16, 2009 3:18 pm Posts: 1726
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 Re: Performance problem - 18x48 w/ 37EFI
don't beleive most of the bullsheet on here. 25 is a good speed for a lawnmower engine on a big ass boat.
30 unloaded with the wind to your back in 18'' of water = 25 in deep water with regular load.
enjoy the boat, there will always be somebody with a faster boat, it is all some folks live for. lol
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Wed May 25, 2016 6:07 am |
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TPerkins
MMT 1000 Club
Joined: Wed Jan 02, 2013 12:59 pm Posts: 1793 Location: Clear Lake, Tx
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 Re: Performance problem - 18x48 w/ 37EFI
I wouldn't call 1848 a big ass boat, but agree with what others are saying in regard to inflated speeds.
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Wed May 25, 2016 6:15 am |
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North LA Hunter
MMT Elite Member
Joined: Mon Aug 02, 2010 8:39 pm Posts: 6976 Location: West Monroe, LA
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 Re: Performance problem - 18x48 w/ 37EFI
The 1848 boats that I've built run about 27-30 with stock motors.
I built a 1852 loaded out and it hits about 27-28.
Don't think your speeds are horrible but the could be better.
Who built the hull?
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Wed May 25, 2016 7:06 am |
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