Hard to Plane - Maxum Boat Owners Club

Hozelitis · 10-15-2017, 03:27 PM

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

mmwjr · 10-15-2017, 04:35 PM

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.

Hozelitis · 10-15-2017, 10:36 PM

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?

mmwjr · 10-15-2017, 11:49 PM

Quote:

Originally Posted by Hozelitis

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?

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.

shrew · 10-16-2017, 02:00 PM

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".

bman440440 · 10-16-2017, 03:42 PM

Quote:

Originally Posted by Hozelitis

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?

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

Hozelitis · 10-22-2017, 02:14 PM

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

bman440440 · 10-22-2017, 02:54 PM

Quote:

Originally Posted by Hozelitis

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.

Hozelitis · 10-22-2017, 03:11 PM

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

shrew · 10-23-2017, 02:31 PM

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

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.

Hozelitis · 11-07-2017, 06:59 PM

Been out of town. A couple questions: is it OK for my 4.3 EFI to be using 1.47 gearing? Would a 4 blade 14x17 prop be correct?
Thanks

bman440440 · 11-07-2017, 07:31 PM

Quote:

Originally Posted by Hozelitis

Been out of town. A couple questions: is it OK for my 4.3 EFI to be using 1.47 gearing? Would a 4 blade 14x17 prop be correct?
Thanks

it is ok for the 1:47 gearing... but now comes the question of how that drive got there?? that drive is for an 350 v8... so going on the idea that for some reason it got changed you need to verify that it actually is a 1:47 not just what the sticker says on the drive... it could have the v6 lower and a v8 upper(where the ratio sticker is) and who knows what the end ratio is now... so I would suggest that you pull your spark plugs and put it in drive (make sure the prop is locked in gear, mark the blade that is closest to top) and put a mark on your crank pulley and spin it 1 time around and see where the prop is now... it should be just past 1/2 rotation (65% of a rotation to be exact) for a 1:47 ratio... if so then get the 14x17 4 blade prop like the one I suggested

Hozelitis · 11-07-2017, 10:42 PM

Quote:

Originally Posted by bman440440

it is ok for the 1:47 gearing... but now comes the question of how that drive got there?? that drive is for an 350 v8... so going on the idea that for some reason it got changed you need to verify that it actually is a 1:47 not just what the sticker says on the drive... it could have the v6 lower and a v8 upper(where the ratio sticker is) and who knows what the end ratio is now... so I would suggest that you pull your spark plugs and put it in drive (make sure the prop is locked in gear, mark the blade that is closest to top) and put a mark on your crank pulley and spin it 1 time around and see where the prop is now... it should be just past 1/2 rotation (65% of a rotation to be exact) for a 1:47 ratio... if so then get the 14x17 4 blade prop like the one I suggested

Thanks much. I’ll let you know.

Hozelitis · 11-19-2017, 12:54 PM

I finally had smooth enough water and my WOT was 3950 rpm by the boat tach, 48 mph by the boat speedo and 45 mph by a speedo on my phone with the boat trimmed out. The prop is nicked a little on one blade, probably smaller than I thought at 1/4" x 1 1/2".
Should I still find the actual gearing or can we tell what prop I need by the WOT?
Thanks

mmwjr · 11-19-2017, 02:30 PM

Going from the 21inch pitch to a 17 inch will increase WOT by about 500 rpm and get you in range. Add a blade will help holeshot but the increase in WOT will be less. Your top speed seems good so if it was me I would go with at 4 blade 17 inch pitch.

Hozelitis · 11-19-2017, 10:56 PM

Quote:

Originally Posted by mmwjr

Going from the 21inch pitch to a 17 inch will increase WOT by about 500 rpm and get you in range. Add a blade will help holeshot but the increase in WOT will be less. Your top speed seems good so if it was me I would go with at 4 blade 17 inch pitch.

Great. I will take your advise and get that prop. I will post the results.
Thanks so much for your expertise.

bman440440 · 11-20-2017, 04:40 PM

Quote:

Originally Posted by Hozelitis

Great. I will take your advise and get that prop. I will post the results.
Thanks so much for your expertise.

also after you get the new prop on make sure you are prepared for the hole shot you will have... it might surprise you the first time so be ready... people are amazed at the hole shot I have with 3 LARGE guys, 32 gal bait tank, and a full load of fuel.

Hozelitis · 11-20-2017, 05:19 PM

Quote:

Originally Posted by bman440440

also after you get the new prop on make sure you are prepared for the hole shot you will have... it might surprise you the first time so be ready... people are amazed at the hole shot I have with 3 LARGE guys, 32 gal bait tank, and a full load of fuel.

Thank You Sir!

Hozelitis · 11-24-2017, 01:02 PM

Happy Thanksgiving.
From what I read each 1” in pitch changes rpm close to 200. If that is correct, and I’m at 3950, and go from 21 to 17 pitch, that will put me at the high range of WOT rpm. I also wonder what a quarter inch in diameter and a 4th blade play into it.
Sorry, I have a boating friend that suggests strongly going to 19 pitch.
It is a 17 year old engine and I don’t want to over rev.
Thanks

mmwjr · 11-24-2017, 01:20 PM

Yes that’s the estimated change in rpm per change in pitch however it differs depending on other factors of prop design such as rake, blade area, ...

Adding a blade will decrease WOT which is why I suggested a 17 inch pitch going to a 4 blade that it think you will like over a 19 inch 3 blade. Your boat your call.