Correct prop size???

[K-Dawg]

I am going to get all of the necessary info but before I do that I have a few questions maybe you guys can help me out with.

1. as far as rpm's go I have an 18hp evinrude tiller 2 stroke engine. Im not sure how to measure the rpm's on this. Can I get a tachometer to attach to this type of engine and if so how would I go about doing that and roughly how much do they cost?

2. I'm am not sure what different types of material/ metals they make props out of. It looks like aluminum, but I dont know for sure. Is there any way to tell.

My boat is about 500-600lbs. 14ft and a tri hull fiberglass. With two people it will get up on plane, with any more it will barely go. I know the pitch is 10 and i have to measure the diameter which i will do. Just wondering if it is just the weight or if a change in propeller will give me better top speed and get me on plane?

sorry for partial info. I will get the rest.

Thanks to all

 

[hwsiii]

Re: Correct prop size???

K, you an buy a Tiny Tach for about $ 40 to get the RPM they are simple to install. And I am sure it is an aluminum prop, and get me the year, make and model of your boat and motor with the gear ratio and I will try to help.

H

 

[steelespike]

Re: Correct prop size???

Check out the tiny tach ,about $40 easy to install.And will fit any 2 cylinder 2 stroke.A gps is good for speed,Props are Aluminum,stainless or composit.
(plastic)there are some old Bronze props out there.Stainless is slightly magnetic quite heavy.On a light reasonably fast boat a 18 will do about 27.
A reduction in pitch will help with a load.Brochure says standard is 9 1/4 X 11
so your allready down one size.you may be able to raise the motor.
Adjust the trim carefully place weight carefully.Check that throttle opens all the way,Check compression.

 

[K-Dawg]

Re: Correct prop size???

HWSIII,

I will get a tach in a few days and get back to you. As far as year make and model. My title is all blank in those areas. It is a trihull and roughly 500-650lbs. Can I use a number or something on the title to find out exactly the make and model?

Steelespike,

As far as the throttle opening all of the way. Is it possible when I have the tiller handle turned all of the way it is not wide open? If so how do I make an adjustment. As it is it is kinda sticky. Guess it needs a lil grease or something?

My general concern is that with two people it runs good, but when u add a third it is like night and day. It just barely puts along. The engine is running but were not movin. And is this bad for the engine? Does it overwork the engine?

I will get the rest of the info and follow up. I appreciate everything.

 

[hwsiii]

Re: Correct prop size???

Look for a hull identifiation number on the bak of the boat or a plate that will give you a lot of information, and steele is right look in the carburetor throat and see if the plate is horizontal when the throttle is wide open and try raising the motor at least one hole up.

H

 

[walleyehed]

Re: Correct prop size???

If you're going to go that far, check the hull for a hook at the transom and any other possible distortion.
This is something that happens with time on most, some have it built-in for other reasons-the hook that is.

 

[steelespike]

Re: Correct prop size???

Are you sure its running on both cylinders?Pull one plug wire at a time and see if it will run.It is possible that the carb isn't opening all the way If you remove the silencer you can look in the carb and see if the throttle plate opens all the way.There is also a sync prosedure that makes sure the carb is picking up at the right point.What year is the 18? Does it have a high speed needle valve?Wow a 500 + lb 14 footer.My 18 aluminum utility is only 375.
And I'm running a 50.
Once you have the tach let us know the rpm with you alone.And maybe with a buddy. Would be great if you could beg,borrow or buy a gps.
I see them at BJs for 99.99.