Anyone tried props for a 90 Etec/cK 16'7"combo?

waldnerrwaldnerr Posts: 1,024 Officer
I recently traded out the 1997 115 Ocean Runner on my c/K 16'7" for a new 90 Etec, and am trying to find the best prop for the new motor. I was running a 12 3/4 X 17" Spinelli 4-blade on the 115 and it works O.K. on the 90 (I can reach about 5300 rpm's max), but I have a bit more slippage than I like (22% at 4000 rpm's). Has anyone played around with props on a 90 Etec? Thanks!

Replies

  • weetzaweetza Posts: 156 Officer
    Funny thing, about three years ago I swapped by 98 ocean runner 115 with a a new 90 ETEC. For my 17'10" Action Craft. I will let you know what I run, but I am not happy with the RPMs I am hitting-barely 5200. Great hole shot. I will let you know what prop I am running, I know its 16 inches with 3 blades, not sure on the pitch. Like to see the responses.
  • waldnerrwaldnerr Posts: 1,024 Officer
    Thanks! Sixteen inches is probably your prop's pitch; most props for outboards with intermediate-sized gearcases such as the Etec 90 have diameters between 13" & 13 3/4". Egret had to get Spinelli to custom-make my current 12 3/4" diameter prop. I can get 5200-5300 rpm's with it, but would like to reduce slippage to get a bit more speed. I've narrowed props down to a 13 1/4" X 16 or 17" 4-blade. I don't want to go too low in terms of rpm; I'm leaning towards the 16", but wanted to get as much info from others as possible. It appears that most folks are running props with 15" pitch on 90 Etecs, but I don't want to drop down that far, especially on a hull as light as the Egret.
  • roto7777roto7777 Posts: 2,545 Captain
    That will be a nice running boat!
    [SIGPIC][/SIGPIC]
  • waldnerrwaldnerr Posts: 1,024 Officer
    Absolutely, Robby - it always has been! The Etec is a lot quieter than my old 115, and the new 90 and old 115 weigh within three pounds of each other. The 90 Etec also has a built-in oil reservoir, which helps clear out my rear starboard compartment. Because the hp on the 115 was measured at the powerhead and the 90 is measured at the prop, the actual power output of the two notors is much closer than the numbers indicate. What I can't figure out is the difference in rpm's at a given speed. Both outboards have a 2:1 gear ratio, but I used to achieve 25 mph at about 3200 rpm's; now I reach 25 mph at 4000 rpm's with the same prop and set-up. The tach seems to be reading properly. This one has me stumped!
  • waldnerrwaldnerr Posts: 1,024 Officer
    I should have mentioned - current was the same during all tests.
  • FlatsBoyFlatsBoy Posts: 1,371 Officer
    Were those analog gauges you were getting your info from with the old motor. Does the new motor have digital gauges now or are you using the same ones from the old setup?
  • trponhuntertrponhunter Posts: 248 Deckhand
    waldnerr wrote: »
    Absolutely, Robby - it always has been! The Etec is a lot quieter than my old 115, and the new 90 and old 115 weigh within three pounds of each other. The 90 Etec also has a built-in oil reservoir, which helps clear out my rear starboard compartment. Because the hp on the 115 was measured at the powerhead and the 90 is measured at the prop, the actual power output of the two notors is much closer than the numbers indicate. What I can't figure out is the difference in rpm's at a given speed. Both outboards have a 2:1 gear ratio, but I used to achieve 25 mph at about 3200 rpm's; now I reach 25 mph at 4000 rpm's with the same prop and set-up. The tach seems to be reading properly. This one has me stumped!

    simple answer - the motor may be close to the same power - but it is not the same - so it requires more rpms. I would assume the max rpm range is slightly higher on the new 90 also?
    *Previous - 2000 Egret 189 carbon w/ vmax 150 - twin rotating prop
    *Previous - 2008 Egret 189 carbon w/ ETEC 150
    *Previous 2010 Beavertail Vengence w/ETEC 90
    *Current - 2015 Beavertail BTV w/ Suzuki 90
  • waldnerrwaldnerr Posts: 1,024 Officer
    They're the original analog gauges from the 115 Ocean Runner. The folks who installed the new Etec said they should work fine, but the tach is the obvious culprit, although it seems fine. The speed readings were taken from two GPS's simultaneously, and both read the same.

    The problem is that two motors with the same gear ratio should push a boat at the same speed when turning the same rpm's if they throw the same prop, regardless of any power differences. That is, at 3200 rpm's, if one outboard pushes the boat at 25 mph, so should the other, if everything else is equal. The difference in the power generated by the motors would be seen in the amount of throttle necessary to achieve those rpm's. However, I'm not seeing this. Maybe a digital tach is in order?
  • FlatsBoyFlatsBoy Posts: 1,371 Officer
    waldnerr wrote: »
    They're the original analog gauges from the 115 Ocean Runner. The folks who installed the new Etec said they should work fine, but the tach is the obvious culprit, although it seems fine. The speed readings were taken from two GPS's simultaneously, and both read the same.

    The problem is that two motors with the same gear ratio should push a boat at the same speed when turning the same rpm's if they throw the same prop, regardless of any power differences. That is, at 3200 rpm's, if one outboard pushes the boat at 25 mph, so should the other, if everything else is equal. The difference in the power generated by the motors would be seen in the amount of throttle necessary to achieve those rpm's. However, I'm not seeing this. Maybe a digital tach is in order?

    New tach is in order.
    :thumbsup
  • waldnerrwaldnerr Posts: 1,024 Officer
    I'll put in a call tomorrow. Like chicken soup - it couldn't hurt!

    Thanks!!!
  • roto7777roto7777 Posts: 2,545 Captain
    My guess it is in the prop. I think the etec is slipping somehow midrange, and power is being lost.
    [SIGPIC][/SIGPIC]
  • waldnerrwaldnerr Posts: 1,024 Officer
    I ran it again yesterday and took speed readings at various rpm's while using a Stiletto 13 1/4 X 17" 3-blade instead of the 12 3/4 X 17" 4-blade Spinelli. The speed was still a bit low at a given rpm: 35 mph at 5000 rpm's, indicating 13% slippage - a bit high, but within normal limits. A 13 1/4 X 16" 4-blade may get me dialed in, and put me in the middle of the Etec's max. rpm range (5000 - 5500 at full throttle).

    Thanks for all the help, guys!
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