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Old 10-15-2017, 03:27 PM   #1
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Default Hard to Plane

Hello,
New to Maxum boats. We have a 2000 1900SR with EFI 4.3. My mechanic says it is running great. If we have two 130# people in the back seat this boat will not get on plane unless they move up front. Is this normal behavior? I think this boat has 210hp. It has a 14.25 x 21 prop. Should I change props?
Thank You
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Old 10-15-2017, 04:35 PM   #2
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The 4.3 MPI is rated at 220HP. What is the WOT for the boat? Should be 440-4800. If you don't have trim tabs you should consider either true trim tabs or smart tabs.
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Old 10-15-2017, 10:36 PM   #3
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Thanks for the reply. I haven’t had smooth enough water to figure the WOT. First day I had it at 40 mph at about 3400 rpm by the gauges trimmed out.
Are smart tabs a decent choice or are trim tabs that much better?
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Old 10-15-2017, 11:49 PM   #4
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Quote:
Originally Posted by Hozelitis View Post
Thanks for the reply. I havenít had smooth enough water to figure the WOT. First day I had it at 40 mph at about 3400 rpm by the gauges trimmed out.
Are smart tabs a decent choice or are trim tabs that much better?
In smaller boats like yours smart tabs work well however trim tabs give you the ability to adjust if someone moves from side to side.
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Old 10-16-2017, 02:00 PM   #5
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Overall, fairly normal for IO's in this class. By class, I mean bowriders and 'family style' recreational boats. I qualify that before someone comes in and says "My Donzi never had a problem like that".
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Old 10-16-2017, 03:42 PM   #6
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Quote:
Originally Posted by Hozelitis View Post
Thanks for the reply. I havenít had smooth enough water to figure the WOT. First day I had it at 40 mph at about 3400 rpm by the gauges trimmed out.
Are smart tabs a decent choice or are trim tabs that much better?
I have a 1997 1900 SR with a 4.3 carb.... I run a 4 blade 21p aluminum turning point prop... I have a 32 gallon (256 lbs.) bait tank on the swim step, 5 men (2 of them 300+ lbs.) a 100 quart ice chest of beer/food and a full 35 gallons of fuel when we go lobstering (and everybody sitting behind the windshield) and I have little problem getting on plane... at 3400 rpm and 40 mph it sound like you have more pitch in your prop than 21... if you do truly have a 21" prop is it possible that the outdrive was replaced with a v8 (1.47/1.62 gear ratio) drive? yours should be 1.81... look on the sticker on the port side of the drive for the ratio.

FYI true trim tabs are the way to go if you feel you need something like that... and no I don't have any tabs
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Old 10-22-2017, 02:14 PM   #7
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I was probably wrong on the speed and rpm. Have not checked WOT yet.
It is a 14.25 x 21 3 blade prop...It does have a 1.47 outdrive.
It had a hydrofoil on the outdrive that I removed and there are holes left over.
The prop does have a 1/4" x 2" nick on one blade near the outside tip.
I just find it hard to believe a 19' boat with a 4.3 EFI can't get on plane with such a small load no matter where they sit.
I appreciate all the responses.
Cheers
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Old 10-22-2017, 02:54 PM   #8
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Quote:
Originally Posted by Hozelitis View Post
I was probably wrong on the speed and rpm. Have not checked WOT yet.
It is a 14.25 x 21 3 blade prop...It does have a 1.47 outdrive.
It had a hydrofoil on the outdrive that I removed and there are holes left over.
The prop does have a 1/4" x 2" nick on one blade near the outside tip.
I just find it hard to believe a 19' boat with a 4.3 EFI can't get on plane with such a small load no matter where they sit.
I appreciate all the responses.
Cheers
1st... the 1.47 drive ratio puts you at a 17 prop for your boat... here is IMO what would work best ---> https://www.amazon.com/Turning-Point.../dp/B00NQ4P5RA

2nd... leave the hydrofoil off until you get the new prop and test with your normal load... if there are no issues leave it off... if it seems to need a little help getting the stern up then put it back on... I have a "stingray" hydrofoil on mine and I like it because I generally have a lot of weight in the stern and it works well.

3rd... the nick on the prop is NO BUENO!! that will cause drive vibrations and cavitation.
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Old 10-22-2017, 03:11 PM   #9
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Thanks much. Most people say NOT to use the hydrofoil.
I'm now thinking of replacing the prop with what you suggest to see if my hole shot is better before I install smart tabs (trim tabs are just too expensive).
Any idea on the weight of this boat? There is a set of smart tabs very cheap I'm looking at.
Thanks again
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Old 10-23-2017, 02:31 PM   #10
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Quote:
If we have two 130# people in the back seat this boat will not get on plane unless they move up front.

Quote:
Originally Posted by Hozelitis View Post
I was probably wrong on the speed and rpm. Have not checked WOT yet.
It is a 14.25 x 21 3 blade prop...It does have a 1.47 outdrive.
It had a hydrofoil on the outdrive that I removed and there are holes left over.
The prop does have a 1/4" x 2" nick on one blade near the outside tip.
I just find it hard to believe a 19' boat with a 4.3 EFI can't get on plane with such a small load no matter where they sit.

Your original post states that this occurs when they are sitting in the back. You also never mentioned that the prop has damage.

hydrofoils provide lift to the hull through the drive and transom assembly. You'd be better off with trim tabs. I would run through the Merc prop calculator and determine if you're over-propped. I would also get the max rpm at WOT.
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