Proper prop for my boat..

[oxbeast1210]

1) Performance issue you are trying to correct.
Boat struggles to get on plane unless extra weight on bow
even then it still slow to get up


2) Current prop manufacturer, model, aluminum or stainless as a minimum.

10-2/3 x 11-1/3 RH Michigan Wheel Michigan Match Propeller ,aluminium

3) Current prop diameter and pitch (required).

10-2/3 x 11-1/3
4) Wide open throttle RPM and speed with an average load (very helpful)
5300

5) Engine/drive make, model, year, and HP
40 hp tohatsu M40C 1989

6) Boat make model, year, length and weight
sunliner sunmate center console 14 ft weight unknown

IM trying to figure out if my current prop is appropriate once on plane boat runs pretty quick it almost feels
like the prop doesnt gram enough water unless someone sits on the bow..

the boat has a 12 gallon gas tank in the stern and also 2 batteries under the center console
usually 2 adults fishing on it there is a hand controlled trolling motor on bow.


thank you if you need more information please let me know


so far I have tried adjusting the manual trim to every hole the best results were hole number 3 from transom
also tried a 4 blade prop 10 pitch but only achieved 3200 rpm at wot .
thank you

 

[steelespike]

Re: Proper prop for my boat..

Can you get the gps speed at 5300. Some cells have a gps app.
Is the motor in excellent tune with a good looking prop.
Does the throttle open all the way?
Are you sure the 4 blade is a 10" pitch. What was the diameter?
Could you get by with 6 gallons in the tank?That would save close to 40 lbs just where you need it most.
Is the anti vent platy(just above the prop) about even with the bottom?
Upon further thought I think we're dealing with about 1200 pounds with 2 aboard maybe a little more
with gear and a full cooler. Your 11 1/3 is right in the middle of the size list.
Perhaps a 10-" pitch would help. Should add about 200 to 300 rpm better hole shot
Not sure about top end it would depend on your present speed.

 

[oxbeast1210]

Re: Proper prop for my boat..

Can you get the gps speed at 5300. Some cells have a gps app.
Is the motor in excellent tune with a good looking prop.
Does the throttle open all the way?
Are you sure the 4 blade is a 10" pitch. What was the diameter?
Could you get by with 6 gallons in the tank?That would save close to 40 lbs just where you need it most.

yes ,motor is good and prop is in great shape
4 blade prop is 11.4x10
I tried going out on half a tank and it didnt help
ill get gps speed next time if I were to guess id say about
30mph

 

[oxbeast1210]

Re: Proper prop for my boat..

yes ,motor is good and prop is in great shape
4 blade prop is 11.4x10
I tried going out on half a tank and it didnt help
ill get gps speed next time if I were to guess id say about
30mph

throttle does open properly

 

[oxbeast1210]

Re: Proper prop for my boat..

Should i go down to 9pitch prop?
thanks

 

[steelespike]

Re: Proper prop for my boat..

A 9" would surely help your hole shot. But lets see what your speed is.
I'm wondering if something like Smart Tabs carefully adjusted might be a better choice.
I think a 9" will cost a lot of speed.

 

[oxbeast1210]

Re: Proper prop for my boat..

ahh Makes sense good call sir I will get you gps speed tomorrow
thank you!!

 

[oxbeast1210]

Re: Proper prop for my boat..

Forgot to mention it has a dolfin type of device installed

 

[Jlawsen]

Re: Proper prop for my boat..

The problem you're experiencing is that the boat is having a hard time getting up on top of the bow wake. Normally a 25hp motor can do that with ease on a 14' boat so a 40 shouldn't have any problem. I run a 10x12 on my 16' with 60 and it gets up on plane very easily.

One of the questions you didn't answer was if the motor cavitation plate is 1" above the keel. If it's lower, it will cause the bow to lift excessively and make the boat plow. That increases the height of the bow wake and will make it more difficult to plane. When you add forward weight you're raising the transom (fulcrum effect) and thereby lowering the bow wake and the result is that the boat comes up on plane and you go faster. I think you're original prop is probably correct.

 

[oxbeast1210]

Re: Proper prop for my boat..

Thank you for taking the time to read my post
I checked the cavitation plate and it believe it is
about an inch or two lower then the keel

 

[oxbeast1210]

Re: Proper prop for my boat..

pics

 

[Jlawsen]

Re: Proper prop for my boat..

It does look low. You should try to raise it up so it's at least even with the bottom. If it was mine I would ditch the whale tale. As it is, it could be contributing to the problem rather than solving it.

 

[oxbeast1210]

Re: Proper prop for my boat..

JLawsen Sorry for my stupidity but how would I raise it? the motor bracket does not have other holes ?
I will remove the tale tonight and see how it does tomorrow.

 

[steelespike]

Re: Proper prop for my boat..

When making changes do one at a time and compare the results.Too many changes at once makes it hard to know what helps/hurts.
The tail may be helping hole shot but it appears it is being dragged through the water when on plane slowing the boat and perhaps making it handle strangely.
looking at the angle of the motor it seems trimming up (prop farther from boat)would improve speed.
But might slow hole shot.Raising the motor may improve hole shot and top speed.The idea is to get as little motor in the water as possible without experiencing too much ventilation.
Raising your motor is pretty simple loosen the clamps and raise the motor and put a 1/2",1"
or an appropriate size stick to attain some height.As long as the clamps retain a good grip there is really no difference
in the support provided. Once a good height is established there are probably holes in the mount that you can bolt it to the transom II
for extra security.The smart tabs I mentioned are a much better choice than the foil.
I do want to mention the tabs need to be adjusted carefully adding tension a little at a time until just enough help is provided.
To improve hole shot.
I figure your total weight is around 1200 lbs, with a buddy along. Thats a lot for a little hull to get up on the water. That's part of your hole shot struggle.
When we went from our 15ft utility to an 18ft utility we discovered it planed much easier with much
bigger loads with the same old 25hp Gale.

 

[oxbeast1210]

Re: Proper prop for my boat..

Thank you steelespike that was very informative. The motor is already bolted on.. There isn't much space for me to move the clamps up there's only about an inch left above the current location on the transom.

today I took the boat out again caught a nice redfish while I was out testing it out. Without the tail on the boat would not plane regardless of where the weight was. So the tail does seem to be helping to get on plane like you said but I can see what you mean by it possibly slowing me down on plane.

what plan of action do you recommend I know that there's no guarantee on anything but if it was your boat what would you do?
thanks

 

[oxbeast1210]

Re: Proper prop for my boat..

Thank you steelespike that was very informative. The motor is already bolted on.. There isn't much space for me to move the clamps up there's only about an inch left above the current location on the transom.

today I took the boat out again caught a nice redfish while I was out testing it out. Without the tail on the boat would not plane regardless of where the weight was. So the tail does seem to be helping to get on plane like you said but I can see what you mean by it possibly slowing me down on plane.

what plan of action do you recommend I know that there's no guarantee on anything but if it was your boat what would you do?
thanks

im going to get the smart tabs and go from there is that a good move?
i also found a boat wih a 505 evinude wih power tilt and trim hw wants 500
for it all i hink i can part out the boat and trailer with little out of pocket ...

 

[oxbeast1210]

Re: Proper prop for my boat..

steelespike If you were me would you go down in prop pitch or add smart tabs?
It has also been stated that I may have a spun hub. Boat seems to move quickly and
feels like its about to get on plane until about 2700-3000 rpm anything more and it just doesn't feel like
its pushing much water if I go back to about 2700-3000 it starts to try to pick up speed again..
I'm pretty lost with this... From researching on this site seems like when one has a spun prop the rpm
will continue to go up but the boat wont gain speed. My rpm just stop around 2700-3000
I have marked the prop and will be doing the test hopefully tomorrow ..