23CC Evinrude 225 WOT..
 

'86 23CC with a 2005 Evinrude 225. No name, no number prop. So I don't have a clue on pitch and size. No trim tabs (well currently not working)

WOT is currently 5000rpm and 33-34 knots based on boat mounted GPS. Planes out at 3800-4000rpm. Engine is capable of 6200rpm. New throttle cables so next time I'm down at the boat I'm going to pull the cover off the engine and make sure I'm getting full opening on the TB.

I'd like to be able to get redline if I wanted to (for whatever reason there would be for that) but don't "need" to. 40+ knots at a decent RPM would be nice to make the tower run on a calm day that much shorter but again; that's a want not a need.

Should I start messing with prop sizes or leave well enough alone?

it's all about load


that motor should be able to run it's max RPM,with the boat loaded in the condition it's normally ran - read that as,if you're running your boat with 4 people,full fuel and 600lbs of gear - duplicate weight conditons

take the boat out and run it on the pin - wide open throttle...record the max rpm you see

check the height of the motor - antiventilation plates out of the water ?

check that the throttle is opening fully...

a motor that's under the rated rpm is overloaded - people often think it's ok,because they never run it hard - that's incorrect,overloaded is overloaded...


every inch of pitch will give approx. 150RPM - problem with that is,when the hull begins to get some air under it,rpm's will climb...read that as,if you're 1,200 rpm down,you won't need to drop 6" in pitch - 2" in pitch is a big difference

a motor being able to reach it's max rpm,is more fuel efficient and it will last longer - overloading the motor,it greatly reduces the durability of ANY motor...

Is that an E-TEC or Ficht motor? A 2005 would be a BRP motor, probably an early E-TEC, and if so you are seriously over-propped! Pelican is right, it's hard on the motor if you're running a prop with too much pitch!

In addition to the commonly published very wide "Recommended Operating Range" like 5000-6000 rpm, BRP has published the OPTIMUM WOT Operating Range for most of the E-TEC's. Haven't been able to find a chart for a 2005, but optimum is probably similar to the 2007 models, which is 5500-5600 with the max load you normally carry. Even if it's a Ficht motor, I suspect optimum RPM would be similar. This assumes motor height is correct, with AV plate running above solid water when on plane, AND your RPM measurement is accurate! (Analog tachs are notoriously inaccurate - a digital I-Command gauge or an NMEA 2000 compatible chartplotter that gets the rpm signal from the EMM is preferred.)

A good prop shop could probably identify or at least measure your current prop and tell you what pitch it is. IF your height and RPM data are correct, having that information on your current prop will eliminate much guesswork in selecting the correct prop!

15x15 sst2 prop. 6100 WOT going 40 mph. 4200 rpm cruise going 30 mph

You need to make some changes

Thanks for the responses guys.

Little more info, it is a late Ficht motor. The test was done without a loadout and 3/4 tank of fuel. Original tank as far as I know. Only me onboard. Flat sea state.

Tach is new and compatable to the Evinrude tach signal. It is however an analog gauge. So grain of salt... GPS unit, older... Can/Do you calibrate those?

So step one- I'm going to ensure the TB is fully opening. Figured the mechanic would have done that so I didn't check before I took her out... Assumptions and all that.

Step two- Check where the AV plate is height wise. Draw a straight line from the bottom of the hull? AV plate 1" above that line?

If those two check out, take current prop to a prop shop and get it measured.

Sounds like a good plan! If you're testing with a relatively light load, you'll want to target the upper end of the optimum rpm range, like 5600-5700, so that you'll still be ok when fully loaded. When prop testing, besides a full fuel tank, I typically fill the live well and fill a couple of 60-70 qt coolers with sea water to simulate a heavy cruising load.

Years ago I had a new OMC tach that read high by about 300 rpm that led me to pick the wrong prop, so just because it's new doesn't mean it's accurate! Dealer checked the tach and replaced it under warranty. Not 100% sure, but I think the Ficht is similar to an E-TEC in that a dealer or you should be able to plug a laptop with the diagnostic software into the EMM and read rpm and a bunch of other stuff, so yes a dealer should be able to tell you if the tach is accurate.

On the AV plate, I think I'd start with AV plate about 1.5" above keel, measured with motor trimmed so plate is parallel to bottom. I like to get it too high to where prop ventilates on a sudden hard turn and then drop it down a hole. How high you can run it depends a lot on the prop. A good highly cupped SS prop can typically run much higher than a cheap aluminum prop w/o much cup. BTW if the prop you have is aluminum, a good shop can repitch it to get you close to optimum before you spend big $ for a SS prop.

JJ - Where's the 17P mirage plus data???

Doh! Waiting for you to record it ;)

Ran down to dry storage today. Didn't have time to get the boat taken down but it is on the bottom rack so I ran inside and looked at the prop again. Turns out there are numbers on the hub. What I have found is it's a Stiletto Advantage II 14 1/4" X 17P stainless steel.

Also a quick measurement of the AV plate puts it around 1 1/2"- 2" above the keel. I have no more holes to go down but I can go up with the motor.

The TB opening properly is still a variable...

So got a chance to go down to the boat yesterday and check the TB opening. They are adjusted properly and opening fully.

Seems it is time to start playing with props. If I decided to go the cheap aluminum route to find the right prop, will a Stainless prop react the same when I find a pitch and diameter that works for me?

I'm going to start with a 15 X 15 as thehermit stated and go from there.

I think the 15x15 stainless is a good choice. I always liked the larger diameter props for a better ride offshore. I think the aluminum one will turn higher rpm's though.

Is that from deflection in the blade from the softer aluminum?

So if it ends up just above where I want it, moving to a SS with the same numbers will dial it in a little better?

That's a good approach and is what I did when I first started testing props, except that I screwed up by not testing at maximum load! I started out with a Michigan Vortex 4B 14x20P prop; the corresponding stainless prop was the Michigan Apollo, but they added 1/8" to the diameter to compensate for the thinner SS blades! (This comparison is only valid for the same style prop . . . same manufacturer, blade shape, rake, etc.!) The 14.125x20P SS Apollo initially looked like a killer prop, giving me about 5.0 mpg at cruise and almost 50 mph @WOT with a real light load at ~5200 rpm. However I then found out that the optimum WOT RPM for my motor was 5300-5500, and one day when I had 6 divers on the boat I discovered it would only turn about 4600 rpm and took forever to get on plane, so I was seriously over-propped! I ended up running a 15x15 4B PowerTech prop that will turn 5400-5450 pretty much regardless of load, and the boat jumps on plane easily with a heavy load at less than half throttle! It also has great stern lift and will hang on plane easily at about 12 mph. 3 blade props are typically faster and more efficient, but I need the extra stern lift of a 4B because my boat is so stern heavy with the bracket and relatively heavy motor (although it's about 50 lbs lighter than equivalent 4-strokes.

The blades on an aluminum prop have to be thicker to minimize deflection because aluminum's elastic modulus (stiffness) is only about 1/3 as stiff as SS. In other words an aluminum part will deflect 3X as much as a dimensionally identical steel part with exactly the same load on it! A SS prop with a given pitch and diameter will typically spin a little faster than it's aluminum twin because of the difference in blade thickness.

An aluminum prop is easy to modify if it needs to be tweaked to really dial it in. A good shop can repitch it to a lower pitch if it doesn't turn enough rpm or add some cup or more pitch if it over revs. That way you can get it dialed in just right before spending big $ for a SS version. (Make sure you test with at least as much load as you normally intend to carry. I always test with full gas tank, full live well and galley seat water jug, plus 65 and 70 qt coolers filled with sea water for ballast, because I run pretty heavy when diving or cruising.) I would also pay attention to min planing speed, because there are times when running offshore, that it's nice to be able to slow down but hang on plane to keep from beating up your passengers. (This is much more important on a much lighter 20, which tends to start going airborne at about 20 kts when seas get over 3'!)

Not exactly the same. Pretty sure PropGods will work with on selecting from various props if you can't get a local dealer to.

X2, Cam's right, Ken Reeves at PropGods in Sarasota has been very good to members of this site. "0" guesswork, as he seems to "nail it" every time.

How do you guys get in touch with Ken at prop gods? Just call and ask for him? Or email him or what?
You Florida guys stop by in person?
Feel kind of weird just calling him out of the blue from the northeast to pick his brain about props...

Propgods
 

Yes, have both e-mailed and talked to him in person. (KR@propgods.com or 941-735-5808) He just ships it UPS or Fed-Ex and I'm an hour away, but my time is VERY valuable!

Relax, He's used to dealing with us weirdo boaters!

Looks like either works

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Tried out Bigshrimpins 15.5x17 p Mirage Plus

Wow what a stern lifter!

Numbers:
3400rpm 12.3 mph- min plane
4200rpm 31.6 mph
4500rpm 34.6 mph
4600rpm 35.3 mph
5400rpm 43 mph-WOT


In the end I went back to the 15x15 sst2. I would love to hear who is using a 15p mirage plus

I tried a 17 p on my 20 w 150 and damn a stern lifting bitch she is.
Just cant turn it. LOVE that prop.

Emailed him, response back within 2 hours.
:)

Alright guys figured I'd give an update.

Got a 15"X15 prop on the boat and got a chance today to do a couple WOT runs. Boat is now hitting 5700 at WOT and clocking in at 35 knots. Also got the trim tabs repaired. Really woke the boat up. 4000 is seeing 26 knots and 3500 is at 20. Pretty happy with the results.

Prop is a 15"X15 Solas Rubex alluminum.

Nice !

Yeah I'm happy. Combination of prop and tabs really makes a difference. Would like to raise the motor up a hole but that's just being nit picky at this point.

Boat got on plane very quick. Less harmonics at WOT. Can level the boat out as needed to vastly improve ride.

Basically I'm a believer. Put the time in to get your prop right and get tabs on the boat. Very worth it.

Raise it, you might be even happier. The right set up will make a good hull perform correctly. Pitch and diameter of a prop matter but rake, cup and blade design will dramatically effect performance also.

I bet quality of prop can also make a difference. Especially with this one being very entry level in design. I'm happy to be at the dial in stage instead of scratching my head as to why it wasn't hitting correct rpms.

Sounds like you got pretty close on your first shot at a prop! (Is it a 3B or 4B prop?) However before you jump to a SS prop, I'd still raise the motor another hole. Did you get a look at the AV plate while up on plane at a normal cruise speed? It's important to get the height correct before fine tuning the prop. Raising motor might give you some more rpm, but if you had a lighter than normal load you'll lose some rpm if you add weight, so load her up with some trash cans filled with sea water if necessary to simulate your max normal load and try that before spending big bucks for a SS prop. I believe Solas actually makes the props for BRP, so whatever the Solas equivalent is to BRP's 3B Rebel or 4B Cyclone would probably be a good choice. The 4B will give most stern lift and best low speed planing, and the 3B might give a little more WOT speed and mpg.

It is a 3B 15"x15P.

Well I wanted to take a look at where the AV plate was but I had my mother-in-law taking a ride with me. When I told her to take the wheel for a second she made some sort of squeaky noise that I think means displeasure.

So I'll have to get a look with the new prop. I did look with the old prop and it was between the AV plate and the LU flange. Not sure if this new prop is going to change that along with the trim tabs now working. So I'll hold off raising the motor until after I get a chance at a longer sea trial.

Then I'll think about getting a nice SS prop. $$$$

The old omc sst was an entry level stainless prop that works great with the SeaCraft hull. It had a decent amount of cupping on the trailing edge of the blades that provided some stern lift. There's a few of those still around. Avoid the sst 2, as it has cupping on the tips that provide bow lift.
A stiletto bay pro 3 is what's on mine. It's a 4 bladed 14 1/4 x 15 with low rake and lots of cup on trailing edges and tips. Picks the whole hull up.
Another member had one of their 3 blades that worked real well also.

When I bought my 1983 23', it had a 235 on it(in 93), it had a 15x15 prop. The same prop worked fine on a 200 Ocean runner. When I put on a 225 Yamaha ox-66 Saltwater series, I tried a couple different props. I settled on a saltwater series 15 1/2 x 19. After a test ride with a factory rep, I was able to exchange it for a 15 1/2 x 17. It was still a little over-propped, but close and I loved the way the boat rode with the prop.
I then bought my current motor, a Yam F 225. I put the same prop on it and used it for several years before getting a Solas 4 blade. Since my motor operating range is 5000- 6000 rpm (really 5500-6000) and my motor then turned 6100 rpm, I figured that was close enough. I got to thinking about it and I asked my mechanic. He told me that the motor has a rev limiter at 6100 rpm. So now I'm thinking I could be under propped. By how much, I really don't know.

A good prop shop could probably put a "100 rpm cup" in it that would drop your rpm and improve your efficiency a bit.