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Prop issues on 1978 70hp 3cyl Johnson 70el78c

Nickjankiewicz

New member
Hi all,

I’m new to this forum but have a question. On my 70hp Johnson 70el78c on idle and part throttle motor sounds super healthy and has recently been rebuilt. When going to WOT motor bogs down and never planes out. I have a 13 x 12degree 3 blade on now and that prop seems normal. That motor was put on a 15+foot 1978 fiberglass boat and don’t know if is to much boat for the motor or should I try dropping to a 13 x 10degree prop or 14 x 10degree 4 blade?
 
Something is wrong here.-------I am thinking you need about a 15 / 17" pitch.----Hurry and talk to a shop to check this out !!!----In my opinion your approach is wrong , sorry.-----Problem could be a waterlogged boat too.----I am not there to look this over.
 
Something is wrong here.-------I am thinking you need about a 15 / 17" pitch.----Hurry and talk to a shop to check this out !!!----In my opinion your approach is wrong , sorry.-----Problem could be a waterlogged boat too.----I am not there to look this over.

thank you racerone, I will have it checked out ASAP.
 
first off your numbers are so far out.. first number would be the diameter and 2nd number should be pitch as is 13 x 17 is 13 diameter and 17 pitch....
you have a15ft boat so 15 pitch will be about the smallest............... if your pitch is 21 inc then its too much for that motor on ha boat, drop to a 13x19 and say hell to around 37 mph plus.... being the motor is bogging I would say you have a 21 pitch and thats too much..... pops are NOT measured n degree like you mention.. its firt2 number are diameter in inches and 2nd two numbers are pitch in inches....... re- check your propeller size again....
 
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