Whaler Central - Boston Whaler Boat Information and Photos

Posted by Turpin on 10/27/12 - 11:30 AM

I have been working on motor height and believe I'm now at the correct setting as boat/motor performs drastically better. A/V plate appears to be just about right on top of the water while w.o.t.
My question is, does the 1990 Evinrude 50hp have a rev limiter or is my tachometer slightly off? At w.o.t. my tach indicates 5700-5800 rpm’s. The motor is rated at max 5500rpm’s (and that’s as far as I’ll let it go), I’d thought if it had a rev limiter it would kick in. (typically I cruise around at 4000-4500rpm’s).
My current prop is 11.75”x17 (possibly OMC) and I’m thinking of changing props since I hit max rpm’s and still have some throttle left.

Any thoughts would be greatly appreciated.

Posted by aeriksen on 10/27/12 - 6:26 PM

If you have throttle left you should go to the next highest pitch prop and check your rpm's I don't know about rev limiter of your engine. I'm guessing it really dosen't matter if the rev limiter kicks in or not, if you have throttle left go up in pitch. I'm sure you'll hear other opinions on this.

Edited by aeriksen on 10/27/12 - 6:34 PM

Posted by Turpin on 10/27/12 - 8:18 PM

Yes I'd agree I may need to go up on the prop and from what I have read 1 step in pitch is typically worth about 200rpm's but I'm still curious about rev limiter.
I guess a better question would be, how accurate are tachometers (typically)?

Edited by Turpin on 10/30/12 - 2:41 PM

Posted by dgoodhue on 10/31/12 - 5:23 PM

My 1989 60hp Evinrude has an operating range of 5000-6000. According to the owners manual my rev limiter is suposedly 6700rpm. The highest rpm I have had my motor is 6400 per my OMC tach.

Edited by Joe Kriz on 10/31/12 - 5:53 PM

Posted by Turpin on 11/01/12 - 6:27 PM

My manual says "Full Throttle Operating Range 4500 to 5500 RPM" (50hp @5000RPM). So my question still stands. I'm leaning towards error in tach but it would be nice to know about the rev limiter. Thanks for the input I'll take all suggestions.

Posted by tedious on 11/02/12 - 9:16 AM

Turpin wrote:
I have been working on motor height and believe I'm now at the correct setting as boat/motor performs drastically better. A/V plate appears to be just about right on top of the water while w.o.t.
My question is, does the 1990 Evinrude 50hp have a rev limiter or is my tachometer slightly off? At w.o.t. my tach indicates 5700-5800 rpm’s. The motor is rated at max 5500rpm’s (and that’s as far as I’ll let it go), I’d thought if it had a rev limiter it would kick in. (typically I cruise around at 4000-4500rpm’s).
My current prop is 11.75”x17 (possibly OMC) and I’m thinking of changing props since I hit max rpm’s and still have some throttle left.

Any thoughts would be greatly appreciated.

Rev limiters are typically set somewhat above the WOT range maximum. You would be incorrect to conclude the motor doesn't have a rev limiter based on the fact that it'll spin 2 - 300 RPM higher than the WOT maximum.

It does sound like you could usefully move up a little in pitch, or if you really want to optimize it, stay with the 17 pitch and go to a modern SS prop. You'll probably find that lets you lift the motor at least one more hole too.

Tim

Posted by Phil T on 11/14/12 - 1:38 PM

#10

Turpin -

As I am sure you already know, to determine the most appropriate propeller, we need to know the gear ratio and WOT speed.

Please remember that changing brands and pitch may likely result in worse performance and money wasted.

Is there a part number or serial number on the prop?

Posted by Turpin on 11/16/12 - 3:37 PM

#11

I can't find any number other than pitch and size. The gear ratio is (according to a manual I'm looking at) is 12:29 (0.41).
The thing I've notice is rpm's aren't affected by boat load, only speed seems to be affected. An empty boat (original set up) and just me is 43mph and a fully loaded boat is 38 (2 adults, 1 child and front and rear fishing decks installed). The rpm's under both load conditions is reading (at wot) 5700.