Propeller drilling for improved take off

[stockyjr]

I owned a 115 Johnson on a 16' Ski boat and was advisd to drill a small hole at each blade through the hub of the propeller, this improved the ability to pull skiers out of the water.<br />I now own a 140 evinrude and would like to do the same however I do not remember the hole size and exactly the location for the hole. Can any one help.<br />Thanks<br />John

 

[DJ]

Re: Propeller drilling for improved take off

Stocky,<br /><br />The trick is to start out small and work your way up.<br /><br />The holes need to be drilled in front of the blades. Right at the base or root of each one. This allows some exhaust gases to escape and essentially creating a temporary cavitation. Once the boat gets up to speed the water flows over the holes forcing the exhaust gases out of the hub.<br /><br />Remember, this will not do you much good if you have an incorrect pitched prop for your application. Your engine should turn at 5500 rpm at WOT with no modifications. If you are below that rpm., switch to a lower pitched prop to start with. One inch in pitch is equal to about 200 rpms.

 

[Bear]

Re: Propeller drilling for improved take off

Two links:<br /> http://marinemechanic.com/site/page76.html <br /> http://marinemechanic.com/site/mercury-prop-venting.htm

 

[stockyjr]

Re: Propeller drilling for improved take off

Many Thanks,<br />Going by the info the hole should be positioned 16mm from edge X 16mm from back of blade. I don't remember drilling a 6mm hole I think I will start with a 4mm.<br /><br />Regards<br />John

 

[rmpenton]

Re: Propeller drilling for improved take off

the book tells you exacily how to do it.

 

[stockyjr]

Re: Propeller drilling for improved take off

rmpenton<br />Please advise which book you you are refering to <br />Thanks<br />John

 

[rmpenton]

Re: Propeller drilling for improved take off

my seloc manual for my 115 tells me how to do it in the first chapter.whatever repair manual you have for your motor should tell you

 

[stockyjr]

Re: Propeller drilling for improved take off

RMPENTON<br />Sorry for repeated questions but my manual does not have any details. Could you please confirm that the information in your manual is the same as I have been advised below. <br />""6mm hole should be positioned 16mm from edge X 16mm from back of blade"". <br /><br />Thanks again John

 

[rmpenton]

Re: Propeller drilling for improved take off

stockyjr, is says drill 3 6mm(7/32")holes.layout from the end of the prop where it is closest to the motor,where the blade starts draw a line straight across 5/8 of an inch clockwise and 5/8 of an inch up from the edge of the prop.get the measurements exacily right on all 3 blades before drilling.then look on the inside of the prop and make sure there is no inner ribs there if there are then it can't be done.but ifs its clear then drill them.if drilled in the wrong spots it wont hurt preformance but it wont helo it any so get your measurements as close as possible.if in doubt of the locations draw a picture and e-mail me of how you will drill it and i will confirm the location rmpenton@bellsouth.net