v6 gearcase on 140 looper. gear ratio? too much prop?

3car

Petty Officer 2nd Class
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Apr 2, 2006
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long story short, I bought a 2000 17' javelin venom with no motor, and I bought an 86' evinrude 140 looper that had been assembled from a few different motors. it has a v6 gearcase. the boat is slightly overpowered, and has a 22p raker prop. the problem is, the boat wont get on plane, just digs. once it finally planes out, it only reaches about 51mph by GPS. tach is not working, so I don't know rpms.
I read somewhere that the looper v4 engines that got the v6 gearcase actually had lower gearsets in them. is this true? if so, I may be over propped. from my research, this model boat with 115's typically run a 22p prop to the high 50's, but that is with the smaller lower unit and prop.
I was thinking something was wrong with the motor, but now I'm not sure.
 

jonesg

Admiral
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Feb 22, 2008
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Re: v6 gearcase on 140 looper. gear ratio? too much prop?

You'd probably be better off posting this in the prop forum, they're the experts. Sounds like the set up is wrong, prop too deep in the water etc.
 

3car

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Re: v6 gearcase on 140 looper. gear ratio? too much prop?

thank you jonesg. I guess the main reason I posted it here was to find out for sure if the v4 engines with the v6 lower units actually had different gears. I posted in the prop forum for advice on the set up.
 

ezeke

Supreme Mariner
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Sep 19, 2003
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12,532
Re: v6 gearcase on 140 looper. gear ratio? too much prop?

long story short, I bought a 2000 17' javelin venom with no motor, and I bought an 86' evinrude 140 looper that had been assembled from a few different motors. it has a v6 gearcase. the boat is slightly overpowered, and has a 22p raker prop. the problem is, the boat wont get on plane, just digs. once it finally planes out, it only reaches about 51mph by GPS. tach is not working, so I don't know rpms.
I read somewhere that the looper v4 engines that got the v6 gearcase actually had lower gearsets in them. is this true? if so, I may be over propped. from my research, this model boat with 115's typically run a 22p prop to the high 50's, but that is with the smaller lower unit and prop.
I was thinking something was wrong with the motor, but now I'm not sure.

It's true that the large gearcases look identical. The V4 large gearcase has a propeller gear ratio of 12:27 while the V6 large gearcase has a propeller gear ratio of 14:26.

Externally there is no way to accurately tell if someone has switched the lower units without counting the revolutions. I have run the V6 units on my 140 but I had to drop the propeller pitch considerably.

To compensate between the large gearcases in the canned prop slip calculators use 2.25 and 1.86 respectively: http://go-fast.com/Prop_Slip_Calculator.htm
 

3car

Petty Officer 2nd Class
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Apr 2, 2006
Messages
132
Re: v6 gearcase on 140 looper. gear ratio? too much prop?

It's true that the large gearcases look identical. The V4 large gearcase has a propeller gear ratio of 12:27 while the V6 large gearcase has a propeller gear ratio of 14:26.

Externally there is no way to accurately tell if someone has switched the lower units without counting the revolutions. I have run the V6 units on my 140 but I had to drop the propeller pitch considerably.

To compensate between the large gearcases in the canned prop slip calculators use 2.25 and 1.86 respectively: http://go-fast.com/Prop_Slip_Calculator.htm
Thank you. I have a very strong suspecion thats whats going on with my motor. It feels way over propped when you try to jump. It didnt dawn on me until reading a thread on a go fast forum last night that there may be different ratios in the 6cyl lower end.

Just curious. about how far did you drop the pitch to compensate?
 

ezeke

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Sep 19, 2003
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12,532
Re: v6 gearcase on 140 looper. gear ratio? too much prop?

You can use the calculator to figure it, but to get the same speed at a given RPM, you would have to go from say a 17 pitch to a 14 pitch.

The 140 looper should be set up to reach 5800 to 6000 RPM at WOT with an average load so that you don't lug it. The rev limit on the standard powerpack is 6700. The full throttle range is 5000 to 6000.
 

3car

Petty Officer 2nd Class
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Apr 2, 2006
Messages
132
Re: v6 gearcase on 140 looper. gear ratio? too much prop?

You can use the calculator to figure it, but to get the same speed at a given RPM, you would have to go from say a 17 pitch to a 14 pitch.

I'm sorry, I cant figure out how to use that calculator to determine how much i should drop.
 
Joined
Oct 22, 2007
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Re: v6 gearcase on 140 looper. gear ratio? too much prop?

I'm sorry, I cant figure out how to use that calculator to determine how much i should drop.


IF 22 is the proper pitch prop with a 2.25 gear ratio and you have a 1.86 gear ratio it's:

22 X 1.86 / 2.25 which works out to about 18. That's very very basic, assuming no change in prop slip, but should be in the ballpark.

But again, that's assuming that a 22 pitch prop would be right with the original gear ratio. You really really need to have a tach to make sure you get the right prop.
 

3car

Petty Officer 2nd Class
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Apr 2, 2006
Messages
132
Re: v6 gearcase on 140 looper. gear ratio? too much prop?

IF 22 is the proper pitch prop with a 2.25 gear ration and you have a 1.86 gear ratio it's:

22 X 1.86 / 2.25 which works out to about 18. That's very very basic, assuming no change in prop slip, but should be in the ballpark.

But again, that's assuming that a 22 pitch prop would be right with the original gear ratio. You really really need to have a tach to make sure you get the right prop.

thank you. im gonna figure out the lower unit ratio and get a tach working tomorrow. actually today. lol
 
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