112 johnson prop

[LWB53]

any suggestions on the best prop pitch for 112 johnson on 18.5 center console. it has a 13-1/4" by 15" on it and it will run 32 mph @ 5400 rpm at about 3/4 throttle. no rev limiter on this motor so i have to keep it throttled back.

 

[junior1113]

Re: 112 johnson prop

15 is probably a bit low for this application 19 would be more ideal. really need to be close to 5400-5600 rpm wot, diff between two inches in pitch is close to 300 wot rpm if your 3/4 throttle and at 5400 you could hit 7200 easy i would recomend starting out at a 19 .i ran a 21 ss 18' four winns with 140 evinrude this was a lighter boat though. is that 3/4 throttle really 3/4 or just backed of a little if backed of a little a 17 might do it

 

[LWB53]

Re: 112 johnson prop

It has hit 7000 with my wife driving. She knows better now. I am having trouble making up my mind between 19" and 21". Dont tow much, maybe a tube a couple of days out of the year. And I was looking at a 4 blade Stilleto bay pro 1 prop. But I am not sure if 4 or 3 blades is better. Not really any cost difference.

 

[Dhadley]

Re: 112 johnson prop

A stock 112 won't hit 7000 rpm. Make sure the tach is set right. If it's set onposition 6 the verify the accuracy with a shop tach. You're looking for 5800 rpm with an average load.

 

[LWB53]

Re: 112 johnson prop

Started missing afterit hit 7000 rpm so i investigated and I had lost a cylinder. I was not paying attention to her driving untill the sound of the engine changed pitch. haven't used a shop tach yet but I will. Thanks for the idea. But I do know I want to change props to help increase the load on the engine to make it a little tougher for this to happen again since the motor has no rev limiter. I couldn't find a power pack that had one.