what sizeprob to use

[flick122]

I have a 94 johnson 30 hp outbord and i was wondering if there is another prop thqt i can use i curently have a 10x15 size one on there now but i resently got a new longer and heavire boat and it takes a while to get out of the hole and it boggs down when it has weight but it runs about 25 mph with one person and crabbing gear beboat is 15.5 foot long fiberglass and its exacly like a carilina skiff but made in canada so i want to now if there is a diffrent prop i can use and if it will give me better gas economy to because it burns alot so i would appreciate any help thank you

kyle

 

[steelespike]

Re: what sizeprob to use

To do this right, for the health of the motor and the best performance, we need you to answer the stickys at the top of the prop forum.
The motor needs to be able to rev freely within its rpm range .
With basically no information My guess is you need about a 12" pitch prop.
Something like a tinytach will get you your rpm and a gps for speed.
The 30 will use about 3 gallons per hour at wot.Whether pushing a light runabout or a house boat.

 

[jestor68]

Re: what sizeprob to use

With basically no information My guess is you need about a 12" pitch prop.
.

Good guess. According to the Evinrude tests of their 30 hp; turning a 12" pitch 3 blade prop at 5800 rpm produced 28.3 mph on a 15 ft Carolina Skiff.

 

[flick122]

Re: what sizeprob to use

Ok yeabut wat nimbere on the prop is the pitch the 15 or the 10 or eather

 

[steelespike]

Re: what sizeprob to use

Prop size is always listed diameter X pitch.

 

[jestor68]

Re: what sizeprob to use

Ok yeabut wat nimbere on the prop is the pitch the 15 or the 10 or eather

It should say 10 X 15. The 10 is the diameter, and the 15 is the pitch.

You want one that says 10-(a fraction) X 12. In this case, the diameters are all the same, give or take a fraction of inch.

 

[flick122]

Re: what sizeprob to use

ok thanks to all can you give me links or sites to get one for a reasonablke prise

 

[jestor68]

Re: what sizeprob to use

ok thanks to all can you give me links or sites to get one for a reasonablke prise

The prop section right here at the top of the page. The prises here are the best around.

How bout a Solas 10-3/10 X 12 3 blade for $65.99?

 

[flick122]

Re: what sizeprob to use

would the 4 blade 12 inch picth be better or the 3 blade

 

[steelespike]

Re: what sizeprob to use

Very generally a 3 blade will produce good all around performance with good top end.
A 4 blade should produce better hole shot,stay on plane better at reduced throttle,resist ventilation
seem smoother and respond better around the dock.It will likely have a slightly slower top end.
Usually it is suggested to drop one inch in pitch when going to a 4 blade,but that would depend on how it performs with a 3 blade.
You really need a tach to do this right.

 

[flick122]

Re: what sizeprob to use

ok yess but i had a 14 foot aluminum boat and it riped with this motor and prob that is on it now and i can hear the motor scream running high rpms but with this heveyer and bigger boat the motor dosnt run the sam rpm bc i can hear it in the motor buti waqnt the prop that gets me out of the hole and gives me enough top end speed im not expert at this you guys now more than i do

 

[steelespike]

Re: what sizeprob to use

The 12" pitch suggested should work., The diameter will be right if the prop is intended for your motor.
Without your present wide open throttle rpm and gps speed we can't be very specific.
A 12"prop will vastly improve you hole shot and power.
Without a tach we can't tell if the rpm is where it needs to be with the new prop.

 

[flick122]

Re: what sizeprob to use

it runs about 25 mph i just want the prob that gets me out of the hole faster but dosnt nesisarly have to give me more top end speed

 

[steelespike]

Re: what sizeprob to use

Again the 12" will improve your hole shot and improve your power.
You do need a tach to be sure the motor operates within its rated rpm.
The 12" pitch will definitely let the motor rev.
Thats good as long as it stays within its maximum rpm range.

 

[Silvertip]

Re: what sizeprob to use

Until you determine what RPM the engine is running NOW at wide open throttle with what you consider an average load, we cannot give you any specific recommendation. The best prop is going to be the one that allows the engine to rev at or very near the upper end of the manufacturers recommended rpm band. Therefore, what the engine revs to with the current prop, versus what the manufacturer recommends for WOT rpm is how you determine what needs to be done. If the manufacturer recommends 5500 RPM and you are only turning 5000, you need to drop pitch by about 2 inches (200 rpm increase per inch of pitch). That increased rpm does not mean the boat is faster because rpms are higher. Remember, the prop is taking less bite due to less pitch so the boat moves forward less distance with each rev.

 

[flick122]

Re: what sizeprob to use

ok sounds good does antone know how to hook up a rpm gauge to the motor or at what rpm the motor is recommened to be its limit

 

[jestor68]

Re: what sizeprob to use

ok sounds good does antone know how to hook up a rpm gauge to the motor or at what rpm the motor is recommened to be its limit

If you get a Tiny Tach, the directions come with it....one wire hook up.

You rpm range is 5200-5800 rpm.

 

[flick122]

Re: what sizeprob to use

ok is there a small tack on here that you would recomend

 

[steelespike]

Re: what sizeprob to use

Check on the net for induction tachs like the Tinytach. They work on almost any application, very simple hookup.just be sure to read all info before making a decision.