1974 johnson 115 take off speed

[norman2013]

Hey guys, I finaly have my motor running pretty good now! Compression is good, spark is good, it gets up to speed. I had to oil up the timing arm because it seemed to be stuck a few weeks ago. I just have one more thing I would like to get working properly and that is its take off power. I have it mounted on a four wins fishnski boat and it just doesn't take off fast at all. It takes it a good 20 seconds to get up to speed and start planning out to get up to speen? Any suggestions ?

 

[boobie]

Re: 1974 johnson 115 take off speed

Do a cylinder drop test on it to see if it's running on all four cylinders.

 

[norman2013]

Re: 1974 johnson 115 take off speed

Sorry I forgot to mention that in the first post. It is running on all four. I did one a few weeks ago

 

[racerone]

Re: 1974 johnson 115 take off speed

Wrong prop or the boat is water logged ?-What boat and what is the prop pitch.

 

[norman2013]

Re: 1974 johnson 115 take off speed

It's a 1985 four winns fish/boat with a 1974 Johnson 115, boat has new floor and transom in it. And the prop is not the one that came with I pulled a prop off of a 1977 115 Johnson and am not sure if that was even right. But it seemed to fit like a glove

 

[emdsapmgr]

Re: 1974 johnson 115 take off speed

OMC made many props/sizes which will fit that engine, so it's critical to get the correct one. You did not post what the current prop is that you are using. An OMC prop has the pitch and part number stamped on the end by the prop nut. Please re-post what the pitch is on the prop. In the end, the correct prop pitch is the one that will let the engine run up to the factory stated max rpm's, which is 5500 for that engine. (You can safely turn that engine up to 5700 and still make reliable hp.) If the max it will run is 5300, you have the wrong prop and are lugging the engine. Each prop size change will change the max rpm's about 300 rpm's.

 

[norman2013]

Re: 1974 johnson 115 take off speed

The prop that I have on there now said 389514. And it has an m on it. The prop that came on it is (0) D 3x13.25x17r

 

[emdsapmgr]

Re: 1974 johnson 115 take off speed

A 17 pitch prop would normally be a good holeshot prop on that engine. You should not need to drop to a 15 pitch. I'm suprised that it is a poor performer. Does it let the engine run up to 5500 rpm's?

 

[norman2013]

Re: 1974 johnson 115 take off speed

I have not run it on the 17 inch. It had some nicks in it so I switched it with another stainless that I had. So I have not tested it out yet with the 17 inch

 

[racerone]

Re: 1974 johnson 115 take off speed

???-----Not sure what you are saying here.-----You have not run the motor with a 17" pitch ?-----So what have you run it with??-----------If you post exact information some might be able to give an answer.-Otherwise this is just guess work !

 

[norman2013]

Re: 1974 johnson 115 take off speed

I have the 389514 prop on there right now and that is what I have been running it with. But it does not have very much power at the start. The other prop that I have the one with 17 inch pitch came with the motor but I switched it before running it due to it having a few dings in it. So I'm going to put the original prop Back on and try it out

 

[racerone]

Re: 1974 johnson 115 take off speed

YUK,YUK, ------That part # comes back as a prop with 23 " pitch.-----Therefor it is no wonder that the 70 hp motor can not spin that !!!!

 

[emdsapmgr]

Re: 1974 johnson 115 take off speed

It would be hard for a 135 to spin that sst prop.