Logo
FULL SITE MENU

Prop size bS

J

jreyes41

Member
"Hi again I have a 1975 85hp e

"Hi again I have a 1975 85hp evinrude thats is replacing a 1985hp evinrude that was stolen from my 1985 astroglass bass boat, well I was told that I would have to replace the prop to be able to get the right pitch and size of the prop,is there a way to find out the right pitch i wounf need for this boat. Is a 85hp enough power for 19 foot astrogalss?
thanks Again.
jorge"
 
"Jorge, ran some numbers throu

"Jorge, ran some numbers through the prop calculator for you, based on your boat/motor and a standard load of 2 persons plus "junk"


It kicked out that you can use a 19 pitch (in either a 13 or 14 diameter) and that should give you a top end speed in the mid 30's (35-36 mph). Not excessive for this boat by any means, but will burn alot less gas than say hangin' a 150 off the back...

If you tend to run with more people on board (say two more adults etc), you may want to drop down to a 17 pitch."
 
"Thanks again graham! It has a

"Thanks again graham! It has a stainless prop, do you know how tell what pich it is should there be some marking on the prop it self. I plan to use this boat 4 persons 2 adults and 2 kids should I just go with the 17 pich any advise."
 
Can you tell me again the plug

Can you tell me again the plug # I need for this engine I'am having a hard time finding this champion # l77j4 is this correct or am i missing a #.

thanks
 
"Jorge, the pitch should be st

"Jorge, the pitch should be stamped right into the prop - have a look on the (outside) between the blades towards the gearcase end of things - normally where you would find it...."
 
"As to the plugs, sorry, old b

"As to the plugs, sorry, old book, old number - you can use QL77JC4's as an alternative..."
 
"along these lines of prop que

"along these lines of prop questions, should you change props as to what your going to do on the boat. i have a fairly big pro line and when i go out striper fishing with sometimes four guys and a 40 gallon bait tank and generator and 80 gallons of fuel and equipment, this is a great deal different when i go out with the wife to ride."
 
"Phillip, really you should ha

"Phillip, really you should have perhaps as many as 4 different pitches (or more) to cover different situations and seasons with the boat - selecting the prop that will suit situation/conditions on a "per use" basis.

The two things that affect how your engine works that require a different prop are weight and weather.

Obviously, you add weight to your standard or "normal" load and the engine is going to have to work harder. In most cases, if you drop the pitch by a bit, the motor can adequately compensate.

The second factor (weather). On high temperature, high humidity days, your motor can't breathe as well and labours. So even with a normal load it may lose as much as 14% of it's top end power. That could cause it to be "overpropped".

Usually, if you find a prop that runs well for you in the spring under normal load, and then make your "spare" perhaps 2" of pitch less. The "spare" could be used on the very hot days in summer, or on occasions when you are carrying some extra load."
 
what is the ideal rpms that i

what is the ideal rpms that i should run with a prop and will i have to be careful with the thottle if i am propped up too far
 
"Phillip, ideal rpms would be

"Phillip, ideal rpms would be about 200 below max WOT for your particular model. What do you have?"
 
Back
Top