Change pitch from 17 to 19?

[mark1961]

I have a 15ft aluminium single vee runabout which is powered by a 1982 60hp 2cyl Evinrude and would like a little more top end speed if possible. Would changing from the current alloy 11-3/4 -17 to a sst 11-1/4 -19 achieve this for me? What other noticeable changes negative or otherwise would there be?

Cheers.

 

[NHGuy]

Re: Change pitch from 17 to 19?

You need to read the RPMs first. If the motor is already matched to the prop a taller prop will only make it slower and may cause other problems. If the motor is over revving you can get a taller prop.

 

[kenmyfam]

Re: Change pitch from 17 to 19?

Agree. Need to verify the current RPM at WOT before considering a change.

 

[mark1961]

Re: Change pitch from 17 to 19?

Thanks for the replies, the boat has no tach so i will endeavour to obtain that info and respond. The current prop (11-3/4 -17) is the standard one fitted to this particular motor according to the brp site, not sure if its matched. The other prop i mentioned (sst 11-1/4 -19) is also listed on the brp site as being suitable for my motor.

Cheers.

 

[steelespike]

Re: Change pitch from 17 to 19?

If you read the stickies at the top of the page and the helps at the prop store page
it will help you understand prop selection better,We be glad to help you pick a prop
and clear up any confusion.
Selecting a prop is like selecting a single gear in your car to do everything.
Lower pitches (17) are kind of like 2nd or 3rd gear higher pitches19" more like 4th or overdrive.You need to run the prop that puts your motor near the top of its rpm rating at wide open throttle(wot).A 1" change in pitch will result in about a 200 rpm change,assuming similar material and design.When changing material results are less predictable.A tiny tach is about $47 and easy to install.They have a web site.Be sure to read all the info.
When you get us your performance info we can tell better if your setup is right
and if your prop seems to work.

 

[WIMUSKY]

Re: Change pitch from 17 to 19?

Thanks for the replies, the boat has no tach so i will endeavour to obtain that info and respond. The current prop (11-3/4 -17) is the standard one fitted to this particular motor according to the brp site, not sure if its matched. The other prop i mentioned (sst 11-1/4 -19) is also listed on the brp site as being suitable for my motor.

Cheers.

What link are you going to? When I go to Johnson's site and look for parts, the site shoots me to Evinrude. There, they only list props for V-4 and V-6.

 

[ditchen]

Re: Change pitch from 17 to 19?

What link are you going to? When I go to Johnson's site and look for parts, the site shoots me to Evinrude. There, they only list props for V-4 and V-6.

You are not looking in the right place.

http://epc.brp.com/Index.aspx?lang=E&s1=b73ea431-e4b9-461c-88fd-ce4a39b1a393

From the above link

80 0389029 PROPELLER, 11-1/4 x 19 - sst 1
80 0391014 PROPELLER, 11-1/4 x 21 1
80 0391015 PROPELLER 11-1/4 X 21 - SST

 

[Mark42]

Re: Change pitch from 17 to 19?

You are not looking in the right place.

http://epc.brp.com/Index.aspx?lang=E&s1=b73ea431-e4b9-461c-88fd-ce4a39b1a393

From the above link

80 0389029 PROPELLER, 11-1/4 x 19 - sst 1
80 0391014 PROPELLER, 11-1/4 x 21 1
80 0391015 PROPELLER 11-1/4 X 21 - SST

FYI, those detail links to BRP parts will only get to the login page.

 

[WIMUSKY]

Re: Change pitch from 17 to 19?

Thanks.
In my case for SST, they go from a 11p - 21p. Quite a range....

 

[mark1961]

Re: Change pitch from 17 to 19?

If you read the stickies at the top of the page and the helps at the prop store page
it will help you understand prop selection better,We be glad to help you pick a prop
and clear up any confusion.
Selecting a prop is like selecting a single gear in your car to do everything.
Lower pitches (17) are kind of like 2nd or 3rd gear higher pitches19" more like 4th or overdrive.You need to run the prop that puts your motor near the top of its rpm rating at wide open throttle(wot).A 1" change in pitch will result in about a 200 rpm change,assuming similar material and design.When changing material results are less predictable.A tiny tach is about $47 and easy to install.They have a web site.Be sure to read all the info.
When you get us your performance info we can tell better if your setup is right
and if your prop seems to work.

Appreciate the advice, i will definitely read up on the recommended material.

I have the tiny tach on order (ebay) but its being sent to me from your neck of woods so wont have it for a bit, i asked them to extend the cable provided it wont impair accuracy so i can mount at the helm.

 

[ditchen]

Re: Change pitch from 17 to 19?

FYI, those detail links to BRP parts will only get to the login page.

uhmm,, select view parts catalog and then select outboard johny or rude. Then select the folder with correct HP, year and model. Then you can get into the online parts fiche.

 

[mark1961]

Re: Change pitch from 17 to 19?

I have a 15ft aluminium single vee runabout which is powered by a 1982 60hp 2cyl Evinrude and would like a little more top end speed if possible. Would changing from the current alloy 11-3/4 -17 to a sst 11-1/4 -19 achieve this for me? What other noticeable changes negative or otherwise would there be?

Cheers.

I finally have some data to pass on to try and get this sorted out with the boards expertise, the motor is running at near enough to 5400rpm at WOT, the operating range is 5000 to 6000rpm and my current top speed is 42kph or 26mph (gps). That says to me a taller prop isnt going to do me any good, can anything be done to improve my top end speed, or am i better off sticking with what i have?

Cheers.

 

[Bob_VT]

Re: Change pitch from 17 to 19?

A few of the motor manufacturer's have "performance reports" listed. It is interesting to read them and you will see that the aluminum hulls really do not live up to the fiberglass bass hulls.

I would strongly suggest a tach (easy to wire in) but, will honestly tell you..... you may not see that much difference in performance. Actually w/o a tach you might be hurting the motor by not allowing it to run to WOT. The "butt dyno" tests do not work in this instance

In your recent number's 5400 is good with a 17" and going larger will only drop your rpms...... you might get lucky and run the same exact speed but, be lugging the motor.

 

[steelespike]

Re: Change pitch from 17 to 19?

I would think your setup should run 30 to 35 mph. Before making any changes:
Your antivent plate(just above the prop) should be visable at speed.Usually about even to an inch abovethe bottom.Be sure the throttle opens all the eway.Prop in good shape.Motor in excellent tune.
Does the boat respond when you trim up?If it has a whale tail foil on it take it off for now.
If all checks out it appears you could drop to a 15" pitch. It should pick up youre rpm and may add a little speed.

 

[mark1961]

Re: Change pitch from 17 to 19?

A few of the motor manufacturer's have "performance reports" listed. It is interesting to read them and you will see that the aluminum hulls really do not live up to the fiberglass bass hulls.

I would strongly suggest a tach (easy to wire in) but, will honestly tell you..... you may not see that much difference in performance. Actually w/o a tach you might be hurting the motor by not allowing it to run to WOT. The "butt dyno" tests do not work in this instance

In your recent number's 5400 is good with a 17" and going larger will only drop your rpms...... you might get lucky and run the same exact speed but, be lugging the motor.

Sorry Bob, forgot to mention, I have one of those tiny tachs fitted now, 5400rpm at WOT is the number it came back with.

 

[mark1961]

Re: Change pitch from 17 to 19?

I would think your setup should run 30 to 35 mph. Before making any changes:
Your antivent plate(just above the prop) should be visable at speed.Usually about even to an inch above.Be sure the throttle opens all the eway.Prop in good shape.Motor in excellent tune.
Does the boat respond when you trim up?If it has a whale tail foil on it take it off for now.
If all checks out it appears you could drop to a 15" pitch. It should pick up youre rpm and may add a little speed.

The hull alone is probably a little heavier than you might imagine for a 15 footer, they are of quite sturdy construction, that would be the best way to describe them. I have an old magazine review article which claims the hull weight to be 250kg/550lbs, the deadrise is 13deg. I also tend to run a little on the heavy side, large icebox and usually three adults aboard (no fattys allowed ) with associated gear for fishing, its actually licensed to carry five. The motor is currently fitted with an SE Sport 300 hydrofoil, i have tried trimming up a little but did not notice any improvement. Not sure where the cav plate is at speed, will get someone to check next outing. Props in excellent shape and motor is in extremely good health for age, great compression/tune etc. Will investigate the full throttle situation, that is something i cannot be sure of.....

Thanks.

 

[steelespike]

Re: Change pitch from 17 to 19?

Depending on the height the foil could cause trim effect to be different than normal.
Also could make it difficult to get the bow up at speed.Was 26 mph with a relatively light load?
Based on your typical load after checking your setup without the foil I'm pretty sure you need to go to a 15" prop. This could improve hole shot and speed.

 

[mark1961]

Re: Change pitch from 17 to 19?

Depending on the height the foil could cause trim effect to be different than normal.
Also could make it difficult to get the bow up at speed.Was 26 mph with a relatively light load?
Based on your typical load after checking your setup without the foil I'm pretty sure you need to go to a 15" prop. This could improve hole shot and speed.

Thanks steele, the quoted speed is based on an average load, based on that I know its unrealistic to expect much improvement, would give me some peace of mind to know I have the correct prop to go with my setup though. If everything else checks out and I end up deciding to go with a 15", is it normal practice to choose one with a larger diametre?

 

[Fed]

Re: Change pitch from 17 to 19?

I spent a lot of years fishing out of a mate's 4.9M Lazeabout (it was a factory stretched 4.5M) fitted with a 48HP Evinrude and I can tell you that your boat should go a lot better than it does at the moment.

Your motor has to stay fairly deep due to the external keel extrusion, your cav plate is probably below the bottom of the transom & even though the external keel tapers off at the back it will still disrupt the water flow if you try and raise the motor.
I suspect the foil is probably running under the water at speed so give it a go without it.

 

[steelespike]

Re: Change pitch from 17 to 19?

Thanks steele, the quoted speed is based on an average load, based on that I know its unrealistic to expect much improvement, would give me some peace of mind to know I have the correct prop to go with my setup though. If everything else checks out and I end up deciding to go with a 15", is it normal practice to choose one with a larger diametre?

Usually diameter is a secondary consideration; just stay within about 1/2" either way.Usually you will note that as pitch increases diameter decreases and viceversa.