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11-05-2019 07:22 AM
omc frank
Quote:
Originally Posted by Hartly View Post
Guys is this a true statement that the Evinrude Etec 75hp actually puts out 83HP ? If so how much difference will i see upgrading from an Evinrude Etec 60HO?
No ! it does not 80 may be? but 83 would be breaking the law ratings are allowed to go + - 10% 75x1.1=82.5 no motor company is going to risk government fines and liabilities by giving you too much Hp and a posible safety isue
.
10-16-2019 08:19 PM
Boondock
Quote:
Originally Posted by Bobby Winds View Post
Hey.........isn't this your boat and motor . . . .
Lol looks like fun but that pics has been a bit played out

Nice reply special.
10-16-2019 08:02 PM
Hartly
Quote:
Originally Posted by wh500special View Post
I think for most of Evinrude's - and everybody else's too - normal computer-controlled engines that you should expect they produce their rated power plus or minus some small tolerance. Output would be easy to control and is directly proportional to fuel flow.

You wouldn't think they'd want to risk customer dissatisfaction with a slug, and they don't want to create higher emissions than they promise the EPA. So I would think a 75 hp rated engine would pretty much nail 75 actual horsepower most of the time.

Apparently manufacturers are allowed a +/- 10% variance on their outputs. Evinrude capitalizes on this with their various High Output ("HO") series motors. They have the computer set the output to coincide with the max allowable, so in your case your 60 HP is probably delivering 66 hp max. Bobby's 90 HO should be delivering 99 hp.

Often the advantage to Evinrude's HO series is that the motor has a comparatively higher displacement than a non-HO motor of the same rating. This will translate to increased torque output which, of course, will get a heavier boat on plane more easily. That would be the case with your 60 HO versus the standard 60.

The relationship I have seen for how increased horsepower affects the top speed of a planing hull is to divide the higher horsepower by the lower horsepower, take the square root, then multiply that result by the top speed achieved with the lower horsepower. You can, of course, go the other way and see the effect a lower horsepower would have on the same hull.

V2=V1sqrt(HP2/HP1)

V=velocity
HP=engine horsepower
1 and 2 are subscripts for the two HP cases.

So in your case, assuming you have 66 HP from your current engine and 75 from the new, you'd see a mph increase of 6.6%. So if you're getting 30 mph now, you'll get 32 mph with the larger engine. If you get lucky and get a thundering 82.5 hp version of the 75hp, you can expect a 12% gain...33.5 mph. Unless you do all your running around at full blast, you might never feel the benefits of the higher horsepower.

V2=(30mph)(sqrt[75/66])=31.98 mph


Or - much more succinctly - what DW said.

Whether these modest speed increase are worth it to you is your decision. Chances are that acceleration and planing ability will be pretty similar for both the 60 HO and 75 (same displacement motor). They both weigh the same, so it comes down to preference and cost.

Steve
wh500special. Thank you soooo much for the excellent explanation. After reading what you wrote I fully understand now. God Bless and take care . Tight Lines
10-16-2019 08:35 AM
wh500special
Quote:
Originally Posted by Hartly View Post
Guys is this a true statement that the Evinrude Etec 75hp actually puts out 83HP ? If so how much difference will i see upgrading from an Evinrude Etec 60HO?
I think for most of Evinrude's - and everybody else's too - normal computer-controlled engines that you should expect they produce their rated power plus or minus some small tolerance. Output would be easy to control and is directly proportional to fuel flow.

You wouldn't think they'd want to risk customer dissatisfaction with a slug, and they don't want to create higher emissions than they promise the EPA. So I would think a 75 hp rated engine would pretty much nail 75 actual horsepower most of the time.

Apparently manufacturers are allowed a +/- 10% variance on their outputs. Evinrude capitalizes on this with their various High Output ("HO") series motors. They have the computer set the output to coincide with the max allowable, so in your case your 60 HP is probably delivering 66 hp max. Bobby's 90 HO should be delivering 99 hp.

Often the advantage to Evinrude's HO series is that the motor has a comparatively higher displacement than a non-HO motor of the same rating. This will translate to increased torque output which, of course, will get a heavier boat on plane more easily. That would be the case with your 60 HO versus the standard 60.

The relationship I have seen for how increased horsepower affects the top speed of a planing hull is to divide the higher horsepower by the lower horsepower, take the square root, then multiply that result by the top speed achieved with the lower horsepower. You can, of course, go the other way and see the effect a lower horsepower would have on the same hull.

V2=V1sqrt(HP2/HP1)

V=velocity
HP=engine horsepower
1 and 2 are subscripts for the two HP cases.

So in your case, assuming you have 66 HP from your current engine and 75 from the new, you'd see a mph increase of 6.6%. So if you're getting 30 mph now, you'll get 32 mph with the larger engine. If you get lucky and get a thundering 82.5 hp version of the 75hp, you can expect a 12% gain...33.5 mph. Unless you do all your running around at full blast, you might never feel the benefits of the higher horsepower.

V2=(30mph)(sqrt[75/66])=31.98 mph


Or - much more succinctly - what DW said.

Whether these modest speed increase are worth it to you is your decision. Chances are that acceleration and planing ability will be pretty similar for both the 60 HO and 75 (same displacement motor). They both weigh the same, so it comes down to preference and cost.

Steve
10-16-2019 07:25 AM
Bobby Winds
Quote:
Originally Posted by Boondock View Post
According to Bobby it more than likely puts out about 90+ hp
Hey.........isn't this your boat and motor . . . .
10-15-2019 12:57 PM
DW Back in the day, the rule of thumb was 3mph increase for each additional 10hp. That rule of thumb doesnít apply to the bigger boats with high hp motors common today, but is probably pretty accurate assuming you are talking about a 16 to 17í light weight tiller. If so, you should see about 4 mph increase in speed at WOT.

I donít know if the 75 etec is 83 or not, but note that etec seems to put out more hp than rated hp. Good marketing strategy in my opinion when comparing etecs to the competition. However, I would guess both the 60 and 75 are somewhat equally outperforming the hp rating, so I would estimate a 15 hp differential.

This is all guessing and assumptions. You should go into the etec and other manufacturer performance bulletins and find a similar boat tested with the 60 and 75 hp motors to get a more accurate estimate of the speed differential.
10-15-2019 10:54 AM
Hartly
Quote:
Originally Posted by h8go4s View Post
Measured at the crankshaft or the prop shaft? BTW, this is getting tedious.
h8go4s sorry to have bothered you. I don't know much about engines and am on a fixed budget. Just trying not to make a costly mistake.
Thank you for all your help guys.
10-15-2019 08:38 AM
Hot Runr Guy
Quote:
Originally Posted by REW View Post
Buy one, and have it tested on a dyno and then you will know for sure.

Or you could call the Evinrude factory in Canada and after speaking to the test supervisor they will have the answer if they care to share it with you.


Take care
Quote:
Originally Posted by Juls View Post
All Evinrude motors are built and assembled in Sturtevant, Wisconsin, south of Milwaukee
C'mon Juls, don't let the facts get in the way of a good story,,,,,
HRG
10-15-2019 08:14 AM
Boondock
Quote:
Originally Posted by Hartly View Post
Guys is this a true statement that the Evinrude Etec 75hp actually puts out 83HP ? If so how much difference will i see upgrading from an Evinrude Etec 60HO?
According to Bobby it more than likely puts out about 90+ hp
10-15-2019 07:00 AM
Juls
Quote:
Originally Posted by REW View Post
Or you could call the Evinrude factory in Canada
All Evinrude motors are built and assembled in Sturtevant, Wisconsin, south of Milwaukee
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