New to Boating/ Prop advise needed

[Paradise David]

Paradise Power Boat
13 ft in length
65" across stern
Mercury 2001- 40hp 2 stoke, 2cyl.
Power Trim
WOT- 5000-5500 (Recommended)
10" x 16p x 3 aluminum prop (was on it when I brought the boat)
Weight - 560lbs
Figerglass V-Hull
Rated 3 person or 500 lbs

I only had this boat wet just once so far. Being new to boating, I wanted to learn more of what I was getting into. I have read and learned a lot in the past few weeks.

Ok, we took this boat out (combined weight of us, 335lbs) plus 50lbs of
cargo.
1st thing was it took a long time, 30-45 seconds to get on plane with full throttle, than slowly the RPM rose up to 6500!!
I done some homework here, this is where I would like some advise.
Obvisouly, I need to go bigger diameter and /or pitch, to get my RPM down.
I couldn't find a prop with more pitch for this outboard,shopped many website.
Checking out iBoats props and Solas websites, they have the best selection and price.
I want to get two props ( I plan on pulling tubes, ski, boards later)

Both of theses are Solas props
11 x 15 x 3
10.5 x ?14/13? x 4

4 blade prop for towing rope, 3 blade for playing around.
I think I did my homework correctly.
Please advise, agree-disagree. you wont hurt my feeling!

 

[Silvertip]

Re: New to Boating/ Prop advise needed

13 foot boat, 40 HP motor and it took 30 - 45 seconds to get on plane yet the motor reved to 6500. Did you forget to leave the trailer at the dock? Something is not right. Going to a larger diameter prop or one with more pitch will create more of a hole shot problem but would cut down engine rpm. So since the issue cannot possibly be both ways -- let's look at some possible causes for the discrepancy. First, make sure the tach is correct. There is a dial on the back that should be set on 12P. If that's correct then use a shop tach to veryify the other. If that proved to be the problem and rpm is now within range and hole shot is poor, then you drop down a bit in pitch. DO NOT buy a larger diameter prop than the motor is designed for. It is not necessary and besides, as pitch changes, so does diameter but that all depends on the prop manufacturer.

 

[steelespike]

Re: New to Boating/ Prop advise needed

I have a feeling this is a small sporty boat intended to go reasonably fast
and carry three abreast.Any small boats may be challenged to get on plane as you add weight. And I suspect your passengers probably pretty much have to sit in one place and there is no space forward to help plane.As suggested check your tach once you know its accurate you may be able to select a prop.I do believe your boat will be difficult to plane.Your motor probably has manual trim.If you trim in one notch it will plane better but may run too flat.Your 4 blade will probably get on plane better but may still over rev.You may be able to have the 4 blade repitched if cost effective.If you move the tank and/or battery up under the deck that will help.
Some times (wearing a pfd) if you start on your knees so you can lean forward till it planes it gets up quicker.Power trim is also a big help.

 

[Paradise David]

Re: New to Boating/ Prop advise needed

Thanks for the quick replies

I just got done looking at the back side of the tach. There is a dial there, but no "12p" . Here is what is on the back.
"8" - 12 o'clock postion
"A" - 2 " " " "
"B" - 5 " " " "
"4" - 7 " " " "
"5" - 10 " " " "

With the pointer just to the right of the "8" or 12:30 o'clock postion.
What does all this mean? I dont have any idea! But Ill check out the gage
manufacture.
Yes Steelpike, you would be correct. Its just a little sport boat, sitting on a bench sit, lots of room from dashboard forward, under the deck. I probably could move fuel and battery up front short of figuring out a way to mount them. That would be appx. 60-70 lbs.
The prop on now is a 3 blade 10 x 16p. I haven't brought a 4 blade yet.
I edited my post and put power trim in my spec's.
Any more advise would be much appriecated.

 

[steelespike]

Re: New to Boating/ Prop advise needed

Ok power trim is good.Are you able to trim up all the way for max speed?
One possibility is you could by or make wedges to put between mount bracket and transom. With the thick end up it would allow the motor to tuck in more. Only question is you would trim up somewhat less.Do you have any speed info?
Still need to check the tach.Perhaps you could borrow a shop tach.
Sometimes the switch gets corroded.You could try rotating back and forth
and then set it to the 8.My guess is it should be 8 or A.If it appears there is a notch at the 12:30 spot after you rotate it put it there and see if there is any difference.It seems to me if 6,000 was accurate it would seem that you were really flying with a 16.I think the biggest 40 merc prop here is a 17"

 

[Paradise David]

Re: New to Boating/ Prop advise needed

Ill get the tach check out for accuracy. I have already emailed Gaffrig (manufacture of the tach.) to get some kind of defination of the dial on back.
Speed information? Only had it out once, but speedmeter read 23-25mph. I didnt think it was very acurate myself.
Well, until I get some answers on the tach, Im not buying any prop. I dont want to waste my money on something I dont need.

 

[Paradise David]

Re: New to Boating/ Prop advise needed

Ok,
I got an email back from Gaffrig Gages and according to him, my dial on the back of the tach is wrong.
He told me for outboards motor it should be set to the "B" position.
(copy/pasted)

Email from Gaffrig:

Quote:

David,

What you have there is the selector switch to set the tach for the type of engine you have. If you were told to set it for 12 p (pole) I presume you have an outboard. Most outboards require a setting of 12 pole/6 pulse, that would require the switch to be set to the "B" position.

The other settings would be for different types of engines, the "A" setting is for a 10 pole/5 pulse. Then there would be 4, 6, and 8 settings, those would be used if you had an I/O, the switch would be set to the number of cylinders you have per engine.

Again, just to be clear, it should be set to "B" if you have an outboard.

Thanks,

Ed
Unquote
.......................

I will change and retest in the water, then I will go from there.

 

[Paradise David]

Re: New to Boating/ Prop advise needed

I have changed the setting on my tach. The motor rpm now read correct.
At least at idle it sounds and read more like it should
(800 rpm in the water recommended for idle)
I will now put in the water with the same 10" x 16p prop and see how it does.

 

[Paradise David]

Re: New to Boating/ Prop advise needed

Ok here, the final charter in my testing (hopefully)
I wanted to finish up this post, maybe it will help others with
this problem. We tested today on the water. and again, still takes along time to get on plane.
Teeking the motor some, it is now running great with the Rpm idling where it should be. High speed Rpm, the most I could get out of it was 4500rpm.
Now that all the varables are where they should be, I will now buy a smaller prop
There is a 10" x 16p on the motor now.
10" x 13p should get where I need to be.


To the gentleman @ the top of this post,
if you didnt tell me to check the tach
(not to mention the dial on the back) and see how accurate my tach was,
I would still be lost, most likely buying something I didnt need.
I also brought some wedges to get more angle on the motor for trim. Should be able to tuck the motor up under a little more, help it plane faster.

Silvertip, Steelespike
Thank you
for your help.

 

[Paradise David]

Re: New to Boating/ Prop advise needed

I wanted to finish up this post with all the things I did. Maybe it can help someone else here.

* Move battery to the front of boat (pain in the ( ! ) but worth it)
* Installed wedges- gave me -4 degree from straight up and down
* Installed Nauticus Smart Tabs (Great product)
* Prop - tested 3, settled on 10 3/8" x 14P (3 blade)
Michigan Wheel exchangeable Hubs, very nice design.

* Prop gives me 5800 Rpm and I gain 2 Mph.
* I now get on plane (almost) immediately,
less than 3 seconds after hitting the gas!
* Very stable in a tight turn
* I didn't see much of a fuel saving, actually I run out about 50 yards
from the docks. Ill pay more attention to that.

* 2-11' of battery cable.............................................. $38
Wood - custom box and cradle to secure battery..........$14
Wedges, aluminum - ...............................................$32
Prop - 10 3/8" x 14P................................................ $101
Smart Tabs..(shipping included).................................$117
My Patience............................................................$ Priceless
Total $302

It was worth it all. Im pretty happy now.

 

[hwsiii]

Re: New to Boating/ Prop advise needed

David, would you please give me your WOT RPM and GPS speed, as well as the gear ratio of your motor. I show your motor to have a recommended max RPM of 5,500 RPM and a gear ratio of 2:1, please verify this.

Because if your boat is only going 27 MPH by GPS you have a problem somewhere.



H

 

[Paradise David]

Re: New to Boating/ Prop advise needed

hwsii,
you would be correct on my engine spes.
With all I have done, I have gained 2 mph.
I went back through my post here, sorry for the confusion, my fault.
Before all this started I was getting 34 mph WOT 4800rpm, once I did get on plane.
Now I get 36mph after everything above I have done.

I didnt use GPS, dont have one yet, doesnt really matter on the speed, the speedometer reading is relative after each test I did.
I will check with GPS soon.
Hope that was better

 

[steelespike]

Re: New to Boating/ Prop advise needed

Well youve done a great job.If your not getting any ventilation problems you can probably raise the motor some more.Look for that sweet spot just before venting becomes a problem.Seems with a sporty little boat we could get you to 40 when
alone.Do you feel as you trim out the boat responds well.You don't want the boat to lay down too much it will ride smoother but you will loose a little top end.You might ease up on the tabs a little give up some hole shot for more speed.
As far as the fuel use the 40 will use about 4gph(gallons per hour) at wot(wide open throttle) whether you can reach 30 mph or 36. But if you were going say 10 miles you would use less fuel if it goes faster.You also use less fuel because it gets on plane quicker and of course if you throttle back you'll save even more because now it will stay on plane with less power.

 

[hwsiii]

Re: New to Boating/ Prop advise needed

David, after running the numbers i find your prop slip to be right at 7% and that is very good. Y'all have done a GREAT job, and like Spike says if you can move it up one more notch then you might gain another mile or two an hour.



h