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Author Topic:   NAUSET with E-TEC 90-HP
BillS posted 06-02-2015 07:14 PM ET (US)   Profile for BillS  
[I] finally got a chance to try my new E-TEC 90-HP outboard engine on my 1971 Boston Whaler NAUSET with a clean bottom. The 2015 E-TEC 90hp mounted two holes up, and has a 17-pitch BRP Viper propeller.

With no wind and the lake like glass, and just me (200-lbs) on board, and 12-gallons of gas, here are the boat and engine speeds:

39 MPH on the GPS at wide open throttle 5,700-RPM.

The propeller calculator calculates a 15-percent slip. The old 1998 Johnson V4 90-HP mounted all the way down got 42-MPH at 5,200-RPM with a 17-pitch Michigan Wheel aluminum propeller.

I've read here that the Stiletto propeller is the way to go, and that these propellers tend to act like they have more pitch than the stated pitch. Will a 17-pitch Stiletto propeller get me in the optimal 5,000 to 5,200-RPM range? Or, do I need one with more pitch?

Tom W Clark posted 06-02-2015 09:02 PM ET (US)     Profile for Tom W Clark  Send Email to Tom W Clark     
You need a Stiletto with less pitch, not more. The 13-1/4" x 15" Stiletto Advantage is the usual selection for an E-TEC 90 on a classic 16'-7" Whaler
BillS posted 06-03-2015 12:34 AM ET (US)     Profile for BillS    
Tom--I was thinking I needed a higher pitch Stiletto than 15 to lower the RPM because in this discussion:

http://continuouswave.com/ubb/Forum4/HTML/006348.html

You stated that a 15-pitch Stiletto runs like a 17-pitch SST/Viper. Since I am currently running a 17-pitch Viper and the WOT (5,700) RPM is too high, it would seem logical that the RPM would still be too high with a 15-pitch Stiletto. Can you explain why this is not the case?

Tom W Clark posted 06-03-2015 01:01 AM ET (US)     Profile for Tom W Clark  Send Email to Tom W Clark     
Because you are only getting 39 MPH now.
tedious posted 06-03-2015 01:50 PM ET (US)     Profile for tedious  Send Email to tedious     
Bill, it's the slip.

With the Stiletto, you'd expect a lot less slip. Think of the 15-pitch Stiletto trying to spin up to 5700 RPM - with less slip, you'd be trying to push the boat faster than that 39 MPH. But going faster means more wind and water resistance, so you wouldn't expect to be able to make it all the way back to that 5700, but a bit less. Make sense?

Your motor has a WOT range of 5000-5500, and I'd generally prefer to be in the top end of that, so I would guess the prop Tom recommends would work very well.

Tim

BillS posted 06-03-2015 06:06 PM ET (US)     Profile for BillS    
Thanks Tim I hadn't thought about wind and water resistance as speed increases.

This discussion

http://continuouswave.com/ubb/Forum4/HTML/007984.html

make me think that my original thought of a 17" pitch Stiletto is correct.

My boat is similar to what crbenny has and he is using a 17" pitch Stiletto. Tom told him a 15" pitch would cause WOT engine speed to shoot to 6000 RPM.

It's possible there is too much information on continuouswave.com and I should quit reading and go buy a prop.

tedious posted 06-03-2015 06:23 PM ET (US)     Profile for tedious  Send Email to tedious     
Seriously, go with the 15 pitch. You never know until you try, with an older boat, as they all have some water in the hull so some weigh more than others, but my guess would be you'll spin the 15 to about 53-5500 and end up traveling 41-43 MPH - pretty much optimal as far as I am concerned.

Tim

Tom W Clark posted 06-03-2015 07:43 PM ET (US)     Profile for Tom W Clark  Send Email to Tom W Clark     
If your boat can go 45-46 MPH, the 17" Advantage will be a better fit, but since it only doing 39 MPH now, that makes me think it might not.

It really comes down to the speed potential of the boat. Most guys with the E-TEC 90 on a classic 16'-7" model use the 13-1/4" x 15" Advantage, but there have been a few boats that just seem faster and crbenny's is one of them. Maybe yours is too?

Remember that while the redline for the E-Tec 90 is 5500 RPM the Optimum RPM range is 5000-5200 RPM

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

crbenny posted 06-04-2015 10:30 PM ET (US)     Profile for crbenny  Send Email to crbenny     
Bill, I'm currently mounted all the way up and running the Viper 17" and I'm hitting 43 MPH at 5600 RPMs. The aweful low speed vibration is better with the Viper and I spend alot more time in no wake zones than I do running flat out.

There seems to be a lot of drag in your set up to be taching so high and going so slow. Are you bottom painted?

Chris

BillS posted 06-05-2015 01:10 PM ET (US)     Profile for BillS    
Clean bottom no paint. No water in the foam.

I've ordered the 15" Stiletto. I'll let you know what happens.

boatdryver posted 06-06-2015 09:14 AM ET (US)     Profile for boatdryver  Send Email to boatdryver     
crbenny, what is the cause of the awful low speed vibration you mentioned?

JimL

crbenny posted 06-06-2015 11:14 AM ET (US)     Profile for crbenny  Send Email to crbenny     
The cause of the vibration is the transition point when the motor changes from the lean-burn low speed mode to the power combustion mode. Software improvements have made it better over the last 10 years but it's still there and it would seem that the more pitch you have, the more amplified the transition is. The Viper has less effective pitch than the Stiletto and I'm sure if I ran a 15" prop as most of you do, the vibration would be less again.

I've mounted the engine on a 1/2" sheet of HDPE and cut discs of HDPE with a hole saw and mounted those behind the washers in the splashwell. No signficant improvement.

All is not lost though. E-tec now offers the pontoon series 90. One of the changes from the regular 90 is that the mounts have been changed to soft rubber. This is said to mitigate vibration by more than 40%. It's a quick change out and short money. I'm ordering the mounts this week and will post results.

Chris

Tom W Clark posted 06-06-2015 11:30 AM ET (US)     Profile for Tom W Clark  Send Email to Tom W Clark     
If anybody needs a 13-1/4" x 15" Stiletto Advantage 4.25, I have two of them in stock now that the factory production backlog has eased
rtk posted 06-07-2015 08:17 AM ET (US)     Profile for rtk  Send Email to rtk     
Tom,

I have a 1966 16' with a new 60 horsepower E-TEC. Would this 15 pitch Stiletto work with my combination? I think the gear ratio is 2.8/2.9:1. The Evinrude 17 pitch aluminum propeller gets me 5900 rpms and 32 miles per hour. I'd like to go to a stainless and I've been meaning to email you anyway about this.

Thanks!

Rich

BillS posted 06-17-2015 11:40 AM ET (US)     Profile for BillS    
I tried a 15 inch pitch Stiletto and it worked identical to the 17 inch Viper. So it looks like I need a 17 inch pitch Stiletto or a 19 inch pitch Viper to get the RPMs below the red line.
64nauset posted 06-27-2015 02:00 PM ET (US)     Profile for 64nauset  Send Email to 64nauset     
[Told Tom he wanted to buy a propeller. You should contact Tom via email. His email address, like yours, is available from the user profile.--jimh]
BillS posted 07-02-2015 04:50 PM ET (US)     Profile for BillS    
I installed a 17-inch-pitch Stiletto and now I am getting 41.5-MPH at 5,500-RPM. I wish that maximum engine speed were closer to the optimal 5,000 to 5,200-RPM range, but I am going to call it good enough.

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