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bamabyrd

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i have an 85hp evinrude on a 1

i have an 85hp evinrude on a 16ft astroglass
when i start off it feels like the prop is slipping but its tight on the hub the prop is a steel prop with no markings on it what size prop should this motor use andthe max rpms it should be turning
 
"that engines max rpm is 5500

"that engines max rpm is 5500 you dont want to go any higher than that.i really cant tell you an exact size,it depends on what you do with the boat/go fast/pull skis,tube.want out of hole
quicker etc etc
lets start with what is on it now?(size prop)
what was the engine doing before this(what rpm)?
when you take off does it seem like slipping,out of the hole then catch and go(thats cavitation)
or is it doing it at high and midrange?
try placeing a mark with a permanent marker on the prop and hub . if its out after its been run
the hub is slipping."
 
its on a bass boat fishing onl

its on a bass boat fishing only the prop is steel but not stainless its cavitating when i try to get out of the hole there are no markings on the prop i dont know what pitch it is
 
"it has to be aluminumn.try re

"it has to be aluminumn.try removing the prop nut/
cotter pin and there should be some numbers there.also try coming out of the hole a little slower,{jackrabbit starts}means the prop cant push the boat fast enough,so it sucks air down
and spins the prop with less resistance.
just take it easy fishing is not a race."
 
You will not be able to turn t

You will not be able to turn the prop by hand to see if the bush is slipping...borrow another prop and try that. Your engine is built to rev and i would prop it between 5500 to 5800rpm.
 
i have a 13x19 alum prop i am

i have a 13x19 alum prop i am going to try on it when the weather breakes its been cold here in north mississippi the last few days so i cant do anything now but wait
the prop on it now is painted black and a magnet sticks to it so it has to be steel what diaminator
prop should be used on this
 
"Its a fact reving too low fla

"Its a fact reving too low flat out will over time cause premature engine wear faster than running higher rpms Use a tacho and check what revs you do get and prop it to 5500 as a min, it wont hurt a few hundred revs more."
 
"i disagree,5500 is the max re

"i disagree,5500 is the max recomended by the manufacturer.anything more will cause premature failure.with the right prop there should be no issue keeping it just below or close to max rpm.
i dont understand how you would think running
at 5500 - wot that the rpm is to low ."
 
"Going above 5500 is just stup

"Going above 5500 is just stupidity.
The engine has its max HP at about 5000, which is the spot to hit (slightly above) during normal operating conditions. With light boat, low on fuel and load, You may let it up to 5500-, but not above, unless You want to burn down Your pistons!!"
 
"What a load of crap burn down

"What a load of crap burn down ur pistons, the engine has a roller crank and needle roller big ends and little ends they are designed to rev, most piston problems are caused by overheating,lack of oil, lean mixtures,overloading the engine and the list goes on"
 
That engine run above 5500 wil

That engine run above 5500 will suffer a LEAN condition which again will result in burned down pistons!
 
with the steel prop on it when

with the steel prop on it when its up on plane its turning 5000 rpms max i just happened to think when i had the cavitation problem the other day i had a full tank of gas 18 gal. plus myself and 1 passenger for a total weight of 450 pounds when i ran it last fall i only had half a tank of gas and it did fine
 
"are you happy with that perfo

"are you happy with that performance,you still have a little room for different pitch.
5000 is not bad.
thanks morten,for jumping in ."
 
im going to try it with the 13

im going to try it with the 13x19 on it and see how it does if that works ok if not i will go back to the steel prop and just be slow out of the hole thanks for the info i just dont want to over rev the motor or run at too low a rpm
 
i just ran the boat with the 1

i just ran the boat with the 13x19 prop and it did fine came out of the hole nice with no cavitation plained out nice with good speed at 5000 rpms this i can live with
thanks for all the info it was very helpful
 
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