HP rated at Propeller

[The Force power]

I have a few propellers for a Force / Mercury 85/90 HP, jerryjerry05 has mentioned in different post; that these particular motors were being rated at the prop.

Could anyone educate me on the # for the 85/90/120 HP prop by what numbers they would have?

For example the one I have laying around has the #CW4547 but also CW1321
Has this prop been altered? and to what?

 

[flyingscott]

I do not know of any force that was rated at the prop.

 

[Watermann]

Motors over a certain age were all HP rated at the prop. The only prop numbers I know are the size, such as 19 x 14

 

[GA_Boater]

I guess I don't understand the question. A 90 horse motor with a 15" pitch or a 23" pitch prop is still a 90 horse motor regardless how it's measured. The prop affects the motor's ability to use the horsepower effectively.

As far as #CW4547 but also CW1321 - :noidea:

 

[The Force power]

okay
thank you

 

[flyingscott]

Motors over a certain age were all HP rated at the prop. The only prop numbers I know are the size, such as 19 x 14

It would be motors under a certain age and no force were not.

 

[Texasmark]

On what drives your prop shaft, lawnmowers are a good example of "Brake HP" vs Available HP. Reading the specs on a BS engine to name one, they are rated at 3600 rpm producing their rated hp.....then the caveat: With the basic engine only, no muffler, no this and no that. So the question becomes, what are the losses in the delivery mechanism that effect the power that rolls the prop shaft. I think it was in 1985 era the changeover occurred because who gives a fanny about Brake HP. What you are interested in is what is rolling the prop shaft.

 

[The Force power]

I'm trying to figure out; what prop-size/pitch for 85HP v.s.90HP

 

[racerone]

???-----You must know that is a poor question.------For example a 13-1/4 X17" prop fits on a 45 hp motor and also 140 HP motor from 1969 to 2005 models !-----The difference is the boat / load that these motors are pushing.----Perhaps visit a boat shop and ask them.

 

[The Force power]

a 13-1/4 X17" prop fits on a 45 hp motor and also 140 HP motor from 1969 to 2005 models

I'm aware they would fit, but nobody would have 13"-1/4 X 17 P on a 45 hp (unless maybe some small racing boat/sea-flee
In my scenario it would be a 1990 18' bayliner
Sorry, I asked

 

[racerone]

Do you understand that the propeller attaches to the motor , but fits the BOAT ???----The electrical grid that your house is plugged into runs at 60 cycles per second.-----When the Toronto Maple Leafs are loosing and everybody turns off the TV and lights the grid speeds up.----Say to 60-1/2 cycles per second.----Something you can not see but it happens.-----Those who understand power will then reduce power input to the grid to keep it at 60 cycles per second.-------In the morning when all the toasters come on and the grid slows down to say 59-1/2 cycles they bump up the power in the Nuke plant to keep it at 60 Hertz.-----Bottom line is that work and POWER are not well understood !

 

[Watermann]

It would be motors under a certain age and no force were not.

Motors under a certain year were flywheel rated so yeah over a certain date they were prop rated...

Up for debate but mid 1980's for when each maker came out with prop ratings.

 

[Watermann]

I'm trying to figure out; what prop-size/pitch for 85HP v.s.90HP

Lots of variables there, mainly with the health of the motors and boat type they're used on, but same boat then I'd use the same prop for either an 85 or a 90.

For example on my 18' Starcraft I went from a flywheel rated 140 Merc to a prop rated 115 and used the same 19p prop. The 140 would turn the prop at 5600 rpms and the 115 was only rated at 5250 rpms.

 

[The Force power]

Lots of variables there, mainly with the health of the motors and boat type they're used on, but same boat then I'd use the same prop for either an 85 or a 90

This is what I was looking for.

Thank you to all that put in the time to respond

 

[Texasmark]

...........to a prop rated 115 and used the same 19p prop. The 140 would turn the prop at 5600 rpms and the 115 was only rated at 5250 rpms.

Now having one of those, I wonder why the RPM limitation vs same engine in 3 cylinders I owned was limited to 5500 and the former had a rev limiter and the latter didn't and ran sweetly at 56-5800 on the boat in my Avatar. I do know that the top cylinders are 180* out as are the lower two and the pairs are 90* out seemingly making for a balanced crankshaft power input. Surely there is a reason.