please help 75 hp 1960 johnson lags power

[billbass9]

ive got a 60 75hp johnson the upper id tag reads model #v4sl-12s witch im sure is a 1960 75 hp im not sure if its a longshaft or not its eletric start though and im sure its magneto ign i pulled the battery cable while it was running with the alt/gen unhooked it stayed running strong the bottom id tags read model # vxl-12r i looked this up and its a 60hp (1966?) the reason im wrighting this is when the motor (60 75hp) is ildeing in neutral it seems to run, rev and idle fine but when i put it into gear it runs fine until about half throtle then it just dosent seem to have the power it should it will only do abought 20mph on the 1960 16" glaspar it came on i think now ive tryed adjusting the carbs no diffrence i know probly not but could it be a 75hp motor on a 60hp drive unit (bottom end) and that the thing cant rev like its supposed too also could the prop be the wrong size any body know what size prop it should run i dont have a manual so i cant do the points and im almost sure its in the timing anybody have any suggestions or tips on setting the points thanks for all your time and patience

 

[jimmbo]

Re: please help 75 hp 1960 johnson lags power

These old engines didn't have much if any exhaust tuning, so putting a complete 75hp powerhead on a 60hp midsection shouldn't be a problem. Except for the fat fifties, the heavy duty 60hp, and the 66-68 100hp models all V4s had the same gear ratio 23:20. Not a lot of reduction. Your prop choices are pretty limited with that engine. Most seem to use the 10" x 9 1/4" prop. As for setting the points on the magneteo, it is not easy to explain how to do it without pictures and/or diagrams which show where and which marks are to line up in order to set the points. I reccommend a good service manual. With in info in front of you it isn't difficult to do.

 

[Terry H]

Re: please help 75 hp 1960 johnson lags power

have you got the hi-speed jet adjusted right? That carb should have adjustable lo and hi jets...Have you done a compression test? just a thought

 

[billbass9]

Re: please help 75 hp 1960 johnson lags power

thanks for the info i figgured out how to set the points without a manual it was pretty easy when i got to looking at them. i ligned the flywheel up with the mark on the block set the timing belt to the disturbutor align point, pulled the cover then the pulley there is a ref mark on the dis cam when its ligned up the points are at there widest there i set them to 0.020 as shown on the pulley then turned the dis cam to the next set of points and set them is this correct i think itis seems to run better but dident fix the problem

 

[billbass9]

Re: please help 75 hp 1960 johnson lags power

there is a high speed adjustment and a idle speed adjustment but i cant figure the high speed one out yet there is a black pointer in the middle of the carb on each side there is a plastic screw head (high speed rich,lean needles) i cant figure out how to set the screws i lift up on the pointer and i can turn them but it dosent seem to make any diffrence<br />any thoughts?

 

[seahorse5]

Re: please help 75 hp 1960 johnson lags power

Lift the black pointer up to disengage it from the needle adjustment gears. Set each needle to 3/4 turn open and refit the pointer to the middle. Now you can adjust your high speed operation.

 

[billbass9]

Re: please help 75 hp 1960 johnson lags power

k ill try it thanks. on my carb on the left side there is a choke thing it has three line hookups<br />one on the top and two on the bottom mine is not hooked up, could this make a diffrence in performance? if so does anybody know how to hook it back up? once again thanks for all the help everyone