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Discussion Starter · #1 ·
prop- Mich. vortex alum. 13 1/4 x 17p

3300rpm = 18mph
4000       = 25mph
4500       = 28mph
5000(wot)  = 32mph

perm. tank 12gal,1pob,tm,battery in stern, no jackplate

I guess I need to go to a 13p or 15p

*Stinger electronics automotive meter #3514
rpm range 30=9000rpm
 

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rpm wot range of etec 40 should be between 5500-6000.
Etech 40hp is 5000-6000

http://www.evinrude.com/en-CA/Engines/ETEC_INLINES/ETEC_40_INLINE

Sounds like you got the right pitch for top end. If you move down to a 15p you will gain about 400RPM's give or take either way. You might gain a MPH or two, but then again you could lose a MPH or 2.

If blow out isn't a an issue I would raise the engine a hole and retest with the 17pitch wheel.
 

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Discussion Starter · #4 ·
that is an out of the box thought.....  [smiley=1-mmm.gif].... I like it except for coming up w/ a hoist

I can not trim the motor much  w/o going into porpoising mode ......does that change the thought???
 

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Top - rent an engine hoist from the equipment rental place inside of Lowe's, the cost was about $40/day.  I used the lift to remove the tohatsu & install a jackplate.

Going to a cupped prop created stern lift in my setup, allowing more trim.  Without the cupped prop and stern lift I could trim only a little prior to porpoising.
 

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that is an out of the box thought.....  [smiley=1-mmm.gif].... I like it except for coming up w/ a hoist

I can not trim the motor much  w/o going into porpoising mode ......does that change the thought???
Depends on why the boat is porpoising. Does it do it at WOT trimmed out? Porposing is a very debated topic. It can be caused by many things, trim angle, poor hull design, rocker in the hull, motor to low, wrong prop, weight distribution, and the list goes on and on.

Raising your motor will allow you to gain some RPM's which will hopefully gain you a couple MPH. It will also allow you to run the engine higher without having to add +trim which could help with the porposing. So yes I would probably still try to raise your engine up. Post a picture of your engine height with 0 degrees of trim in relation to the bottom of the boat.
 

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Discussion Starter · #7 ·
Thanks Gramps good idea on lowes will need to check--- I have absolutely zero boat sources up here. What is a cupped prop?::) ;)

CR-The motor at vertical(0 negative trim) puts the cavitation plate at 3/4 - 1" above the bottom of the boat. How much do you think it could go up?

Performance is not a big deal to me . I just want to prop it correctly.It sound like it is screaming now. I am sure a set of tabs would make a diff. but do not want to spend the money. Since, I am fishing in a lake w/ really no rough water

I am leaning towards a 15p prop w/ the 17 as a spare.What is the rule of thumb for rpm v. pitch

I have a buddy coming up in June who used to be a OMC test driver and I am going to ply him w/ brewskies for his input.
 

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Going to a 15" wheel over the 17' wheel will raise your RPM's by about 400, give or take. So it will be screaming even more, if you think it's screaming now. I wouldn't hesitate to run it to the full 6k range though.
In theory (rule of thumb) every pitch will = 200 rpm's give or take; depending on many factors.

In theory a 17" wheel will be faster than a 15" wheel if you can turn the RPM's; as a 19" wheel will be faster than a 17" and so on so on.

And the exact opposite for out of the hole shot, a 15" will be faster out of the hole than a 17" and a 19"

The reason for this is because an engine will require less HP to twist a lower pitch prop, however the higher the pitch prop the further you will travel per revolution of the prop IE a 15" prop will move you 15inches forward for every 1 revolution, as where a 19" prop will move you 19 inches for every 1 revolution.

A cupped prop is where the trailing edge of the blade will have a cup (slight turn upward) which will create more bight, as it does help with lifting the transom it was not originally designed to do so.

Your motor should be as high as it will allow, without having a blow out issue or low water pressure.
All this is rule of thumb, the best way is to test multiple set ups, prop, engine heights etc etc.
 

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Discussion Starter · #9 ·
13 3/4 X15p Mich. vortex 3blade

3000rpm---- 11mph

4000   -----20mph

WOT  -   5600-----30mph

quicker hole shot

lost speed at top end and thru the rpm range

Creekrunner was rt. on

* additional 9lb striper aboard:)
 

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13 3/4 X15p Mich. vortex 3blade

3000rpm---- 11mph

4000   -----20mph

WOT  -   5600-----30mph

quicker hole shot

lost speed at top end and thru the rpm range

Creekrunner was rt. on

* additional 9lb striper aboard:)
Thanks not my 1st Merry go round, lol! only proped probably 800+ boats in my life time.

Did you ever try moving your motor up 1 hole with the 17P?
 

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Discussion Starter · #11 ·
Nope. I am leaving the 15p on rt. now and seeing how it runs w/ 4pob.

Next, I will put the 17p on and raise it one hole. I do not believe It can go more based on running observation from a buddy (ex.OMC test driver )

I will probably stay w/ the 17p for daily use

I will get some numbers and post.

thanks for the input
 

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No need for an engine hoist to raise the motor one bolthole.... Here's how I've been doing it for years.

With the trailer not connected to a tow vehicle put the motor all the way down and rest it on two 4x4's. With someone to steady the motor, raise the tongue on your trailer until there's a bit of tension on the motor against those blocks, remove the bolts, then continue raising the tongue (lowering the stern of the boat) until your motor lines up with the next set of holes, re-insert bolts, secure engine then lower the trailer tongue and you're good to go...
I've done this with much heavier V-4's so a little 40hp should be a breeze....
 

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Discussion Starter · #13 ·
Neat idea.

I was thinking about using my floor jack

now I must reconsider [smiley=1-mmm.gif]
 

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What I've described is just a shadetree boat riggers solution. You either have to raise the motor or lower the transom (while holding the motor straight as its resting on something that won't scuff up your lower unit. The best part is you don't have to un-rig anything else (wiring harness, steering cable, etc) and it's a quick proposition when you just need to change motor height as you're dialing in your prop.
 

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Thats a good idea.
The only "problem" i see is getting silicone or 4200 around and in the bolt holes to seal the transom
 

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Discussion Starter · #16 ·
My thought exactly--- Do the top--tighten---do the bottom.

I ran w/ 15p w/4pob's and found it to be a good match. Good hole shot and a decent crusing speed of 23mph or so.

definetly the way to go for four
 

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you really need to stick with a 15p prop, the 17p is signifigantly overpropped, and no self respecting etec dealer should have rigged that boat to run at 5000 rpm wot

this link is to the etec owners group, good reading even if your prop worries are solved

http://www.etecownersgroup.com/post?id=5396435
 

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Discussion Starter · #18 ·
No dealer involvement. I used merc calculator which gave a pich up to 19p.

The 15p keeps the motor at a higher rpm at all times but increases the rpm required to plane the boat. Also, top speed is reduced and to me it feels like I am running almost w.o.t. all the time which is tiring in more ways than one.

I like the 17p because it gives on a excellent midrange w/ 2 pobs and the fastest top speed as posted.

The fact that it barely gets into the recommemded operating range w/ the 17p and its effect on the motor will still be open to honest debate.

I do believe, after careful observation, that I will raise the motor 1 hole and see what happens w/ the 17p.
 

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Discussion Starter · #19 ·
I raised the engine one hole(3/4") and did not get an increase in speed still at 30mph. I do not think I can go higher because I did experiebce some blowout on a turn when trimmed a little

However, the boat did plane at a lower speed by about 2-3mph and did not have to trim to get top speed but speed stayed the same.

Next time I will have the 17p on and the tach.

We will see.
 

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Yeah the going up 1 hole, will only be useful (Maybe) with the 17p. Your already twisting the 15p as hard as she will turn.

props are all testing, then more testing.

Good luck
 
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