20 foot 1997 Maxum 2050 bowrider propeller question

[gica]

I am using this boat offshore in SOCal to occasionally go to the Channel islands, yes I know it's a bowrider but it works great. I recently rebuilt the Alpha 1 gen 2 drive myself successfully.
So the propeller on the boat is a 14.5x18 aluminum, not the original size which broke, one that I bought awhile back. I am not too happy with it especially in semi choppy waters. The gas mileage sucks but these are gas guzzlers compared to let's say my friend's Trophy II 115 outboard that can do 247 miles per tank. So I will never be able to reach such a performance since I have a 5.7l sterndrive. Carb is rebuilt to specs and adjusted properly. Going to the Channel Islands from Oxnard is roughly a 12 miles trip with another 6 there and coming back I spend roughly 14 gallons of gas. And in semi rough water with winds of over 12 knots even more. You guys probably know about it.
My question is can I get a different propeller that can get the boat on plane below 20mph that it does right now. At WOT I get 4100rpm and 40 miles per hour speed. 30 rpm is 30 miles an hour. This motor specs say 4200-4600 RPM. I don't care about speed since yesterday was the first time I could take it and actually reach 40mph the ocean was the calmest I have experienced in a long time. It's August after all.
So what size propeller and pitch and why? Thanks in advance.

 

[JASinIL2006]

I have always been under the impression that your lowest planing speed was more a function of the hull design than of what prop you're using. Some people report being able to plane at a slightly slower speed after adding tabs; I would say my SmartTabs let me plane about 2-3 mph slower than without them - any slower and the boat starts plowing.

 

[Rick Stephens]

Same for me. SmartTabs reduced my planing speeds. And a prop with a lot of lift will help.

 

[gica]

Yeah I am looking into tabs but given that I have 2 transducers on each side I have to find something that fits.
As far as the propeller, what would you recommend. On another thread they say I should be at 5k RPM!! How can that be if the recommended is 4200-4600? They say 19 or 21 inch prop, won't that reduce RPM?

 

[Rick Stephens]

I'd be trying a stainless 3 blade 17 or even 16 inch, get the RPMs in proper range and keep efficiency at highest. I am not sure what brand and model gives best lift, I never looked specifically for that. That is a well evaluated value on many props.

 

[gica]

And the size I have 14.5 right now. Going to 14x17 doable?

 

[bman440440]

I have the same boat'ish (maxum 2000SR) and I have the 4.3(mildly built to 210 prop HP) in it and A1G2 (1.81) and I run a aluminum 4 blade turningpoint hustler 14.5 X 21P with a Marine Dynamics SR-XPI-1 StingRay Hydrofoil and I can get up on plane at about 17-18 mph with 3 big people, 32 gallon bait tank (full) on the back, 47 gallons of fuel and a kill bag with 80lbs of ice... it will turn 4600 RPM (42 MPH) set up like that and 5050 RPM (54 MPH) with just me and 35 gallons of fuel and empty bait tank... From what you describe you are over propped... Whatever prop you decide on make sure that you get your WOT to 4600 RPM with your normal load of people and gear.

 

[gica]

I have the same boat'ish (maxum 2000SR) and I have the 4.3(mildly built to 210 prop HP) in it and A1G2 (1.81) and I run a aluminum 4 blade turningpoint hustler 14.5 X 21P with a Marine Dynamics SR-XPI-1 StingRay Hydrofoil and I can get up on plane at about 17-18 mph with 3 big people, 32 gallon bait tank (full) on the back, 47 gallons of fuel and a kill bag with 80lbs of ice... it will turn 4600 RPM (42 MPH) set up like that and 5050 RPM (54 MPH) with just me and 35 gallons of fuel and empty bait tank... From what you describe you are over propped... Whatever prop you decide on make sure that you get your WOT to 4600 RPM with your normal load of people and gear.

 

[gica]

I have something similar to your Dynamics SR-XPI-1 StingRay Hydrofoil but not the same brand. My tank is probably 35 gallon, bait tank 20 gallon. I usually fish with my son and maybe another person. I bought the blade 14.5x18 4blade when I wasn't doing any saltwater fishing. I will check my timing to make sure it's ok.
Your 14.5x21 giving you more RPM with a smaller engine sounds good. But I thought the bigger pitch lowers rpm. I have it all backwards. My propeller is not any name brand and it did the trick on a lake even though at WOT it still not up to specs.
So what should I get next for better handling. Probably another boat. Mine looks great and it has been well maintained in and out. Newish upholstery etc.
I do all the work myself.
I need to fix this issue

 

[gica]

This is a link to the propeller diameter measurment and timing check

Dropbox

www.dropbox.com

 

[Rick Stephens]

Your 14.5x21 giving you more RPM with a smaller engine sounds good. But I thought the bigger pitch lowers rpm. I have it all backwards.

No, you have it right. His gear ratio on the drive is much different than yours.

 

[QBhoy]

I have the same boat'ish (maxum 2000SR) and I have the 4.3(mildly built to 210 prop HP) in it and A1G2 (1.81) and I run a aluminum 4 blade turningpoint hustler 14.5 X 21P with a Marine Dynamics SR-XPI-1 StingRay Hydrofoil and I can get up on plane at about 17-18 mph with 3 big people, 32 gallon bait tank (full) on the back, 47 gallons of fuel and a kill bag with 80lbs of ice... it will turn 4600 RPM (42 MPH) set up like that and 5050 RPM (54 MPH) with just me and 35 gallons of fuel and empty bait tank... From what you describe you are over propped... Whatever prop you decide on make sure that you get your WOT to 4600 RPM with your normal load of people and gear.

Had a chuckle at this. Hope you don’t mind. Pushing the boundaries of known physics a little there. 210hp 20ft performance lacking hull, 54 mph. Close to a prop slip figure that mti would kill for…and all with a 4 blade cheapo prop. Legendary! Fair play !

 

[gica]

Been reading, did the turning point wizard and I came down to 14x19, 14.5x17 or 14x17. Any thoughts?

 

[tpenfield]

I think you should try a 17P prop, maybe even a 4-blade. 18 pitch seems a bit high for that boat/engine.

 

[Scott06]

What is your current prop manufactuer and style?
I would suggest you look at a merc revolution 4 , provides nice stern lift and lower plaining speed for me.
they also make an enertia eco aimed at offshore cruise fuel economy

either of these are fairly big props so would think based on your current rpm you want a 16 or 17” pitch . Might be best to find a prop shop and try before you buy. May also want to verify your tach as I would think you would be able to turn more than 4100 RPM with a 5.7 in a 20 foot boat.

 

[gica]

I don't know the manufacturer but it's a 4 blade aluminum. I don't know if 14.5x17 or going down on diameter to 14x17.
How much of a difference does 1/2 inch diameter down make? Also1 inch pitch lower.

 

[gica]

Just thought of something, the accelerator cable that goes on the carb, I have long suspected that it needs some adjustment since when using the remote control to accelerate it doesn't respond right away. I wonder if that limits the amount of throttle that can be achieved?

 

[gica]

Just thought of something, the accelerator cable that goes on the carb, I have long suspected that it needs some adjustment since when using the remote control to accelerate it doesn't respond right away. I wonder if that limits the amount of throttle that can be achieved?

I want to show the timing check again. The mark drifts left and right when idle goes from 630 to 1000 and back. But it doesn't seem to be at 10BTDC, more like 15 to 16 BTDC.

Dropbox

www.dropbox.com

 

[Bondo]

I messed with the cable oiled it and turned the adjustment to make it tighter and now when going to neutral RPM stays a little higher and have to press it by hand to go to 650 as per video.

Dropbox

www.dropbox.com

Is this a cable issue or the throttle lever issue, gets somewhat stuck. I am going to remove the cable see if it does it without it.

Ayuh,..... A properly adjusted throttle cable pushes the throttle arm against the idle adjustment screw,.....
Sounds like you didn't adjust the cable properly,.....

 

[gica]

I took care of that, it was adjusted too close and was killing the throttle so I twisted it out and now it's ok. The rpm varies but it's at 650. The timing in the video varies with the rpm need to find out at what rpm it needs to be to have timing at 10btdc.