joe reeves or anyone with johnson knowlege

[rmpenton]

can anyone tell me what the gear ratio is on a 77 115?mine is two turns on the flywheel to 1 turn on the prop.im trying to figure out why my 16'aluminum flatboat with a 115 on it only does 45mph wide open. i think it should be faster than that. any suggestions will be appreciated.

 

[Hooty]

Re: joe reeves or anyone with johnson knowlege

I think your l/u ratio is 14:26. If it hasn't been changed, the owners manual or the factory shop manual will tell ya for sure.<br /><br />c/6<br /><br />Hooty

 

[rmpenton]

Re: joe reeves or anyone with johnson knowlege

thanks hooty. if it is 14:26 then how many times will the flywheel turn compared to the prop?my manual dont say what the ratio is. i think my gear ratio was changed because of the reasons i stated in my opening post.is it possible that it was changed for trawling or something.wouldnt that make my speed lower.the motor has plenty of holeshot.even on my last boat an 18'bonito.thats why i think its geared lower.

 

[buttonhook]

Re: joe reeves or anyone with johnson knowlege

1.85 <br />flywheel should turn 1.85 (almost 2)times for every turn of the prop.<br /><br />do you have your boat proped right???<br />you need a tach as I found out.

 

[rmpenton]

Re: joe reeves or anyone with johnson knowlege

buttonhook i believe its proped right my wot is 5500rpms so its got to be close.could i go with a bigger prop and a smaller pitch or a smaller prop with a bigger pitch?

 

[Hooty]

Re: joe reeves or anyone with johnson knowlege

What prop are you running now?<br /><br />c/6<br /><br />Hooty

 

[rmpenton]

Re: joe reeves or anyone with johnson knowlege

hooty the prop im running now is a 13 7/8 X 17 with a cup so that would make it a 19"pitch

 

[Hooty]

Re: joe reeves or anyone with johnson knowlege

If you were runnung a 16" pitch prop, you would be running 100% efficient @ 5500rpm and 45mph.<br /><br />c/6<br /><br />Hooty

 

[rmpenton]

Re: joe reeves or anyone with johnson knowlege

hooty what do you mean 100%efficient?with a 17"pitch prop my rpms were to high.how would a 16"pitch make my rpms 5500? thanks

 

[Hooty]

Re: joe reeves or anyone with johnson knowlege

You said 5500rpm and 45mph but didn't know what the pitch of your prop was. All I said was if your prop was a 16" pitch, that engine rpm and boat speed would be 100% efficient. <br /><br />And one more thing. Just because your 13 7/8" x 17" is cupped don't make it a 19" pitch. <br /><br />Hooty

 

[rmpenton]

Re: joe reeves or anyone with johnson knowlege

i got the prop cupped when i had it reworked.i was told a cup adds 2" of pitch

 

[rmpenton]

Re: joe reeves or anyone with johnson knowlege

?

 

[ledgefinder]

Re: joe reeves or anyone with johnson knowlege

Your gearbox is 2:1. As Hooty says, you're wound right out at 45 - wouldn't want to cruise much higher rpm with stock metal reeds. Want to go faster? First thing to mess with, oddly enough, is how the motor is mounted. You want it as high as possible, without losing water pressure, and at the optimum tilt. Search the archives on this, particularly DHadley's posts.

 

[rmpenton]

Re: joe reeves or anyone with johnson knowlege

thanks ledgefinder i have a jackplate on it which gives me 4" of set back.my speed dosent get high enough for me to trim up good.it starts bouncing.if i had more trottle i could trim up a little more.plus my clutch in my prop kicks in and i cant give it full trottle.

 

[rmpenton]

Re: joe reeves or anyone with johnson knowlege

bump