Evinrude Speed

[Truckmechanic]

I have a Evinrude 9.9 on a 1436 jon. Originally when I first took ownership of the motor it was a long shaft and I ran it that way for about 1 year. The boat would fly with the long shaft but I wanted it reduced to have it match my boat.(a 15") After getting it reduced it is now slower than it was. From what I have research I should have gained speed instead of lost, correct? What could be the cause of me loosing speed?

 

[Bugpac]

I have a Evinrude 9.9 on a 1436 jon. Originally when I first took ownership of the motor it was a long shaft and I ran it that way for about 1 year. The boat would fly with the long shaft but I wanted it reduced to have it match my boat.(a 15") After getting it reduced it is now slower than it was. From what I have research I should have gained speed instead of lost, correct? What could be the cause of me loosing speed?

Take a picture its worth a 1000 words, Is it to high, how is it trimmed? wont be trimmed the same being shorter, less leverage on the hull shorter..

 

[Captain Ahab]

How do you reduce a long shaft to a short shaft? Change the entire lower unit?

 

[crazymanme2]

On Johnson & Evinrude motors they have an extension in between the lower unit & mid section you take out.Than you get a short drive shaft, cut shift shaft & water tube.On some there is an extension for the water tube which you just take out.
Presto short shaft motor. =D>
Some Merc use this set up also

 

[Captain Ahab]

Thanks for the explanation - never saw such a thing!

 

[Bugpac]

I believe most of your newer engines have a spacers between the mid section and the foot... :mrgreen:

 

[Truckmechanic]

The pics are with the motor trimmed where I normally run, 3rd hole from the boat. I have tried changing all the trim positions and have never really had any change.

 

[Bugpac]

well, with the difference in leverage maybe the placement of weight has thrown the speed off..

 

[crazymanme2]

From the pic of the rear of the boat,it looks like the motor could come up a bit to make the cavitation plate even with the bottom of the boat.I have to agree with Bugpac.When your lower unit was deeper in the water it put more leverage to lift the bow maybe.Does the bow seem to ride as high as before?

 

[dougdad]

If you are runnig the same prop. as before, I think Bug is on the right track, try shifting some weight to the rear. You may have to put a fin on to get some more lift with the short shaft.

 

[Truckmechanic]

Everything is the same as it was before..

 

[Kobie]

Your motor is way too low, so either make shims to raise the cavitation to even with the bottom of the boat or buy a mini jacker. I have a mini jacker with my longshaft 1980 evinrude 15hp, its just slightly above the bottom of the boat. Don't put a whale tail on there it will only slow it down. From the looks of it you are about 1-2inches too low so the shims idea may not work because the motor clamps will be too high.

Did you have a jack plate for when you were running the longshaft?

 

[Truckmechanic]

Did you have a jack plate for when you were running the longshaft?

No, ran it the same as it is now.

 

[Kobie]

Did you have a jack plate for when you were running the longshaft?

No, ran it the same as it is now.

I dont see how you could have gone faster with a long shaft with that boat. You would have another 5 inches of lower unit in the water, which equals more drag. Most of the time a long shaft on a 15" transom can't even get on plane with that much drag.

Have you gotten a gps reading with the longshaft and the short?

 

[DenisD]

Is there any chance when the lower unit was shortend something internal got out of line? I was thinking maybe the exhaust tube did not get lined up and the engine could run as strong as before. That's the first thing that came to mind. Good luck man I hate it when you try to fix something and it gets worst.

 

[Truckmechanic]

Is there any chance when the lower unit was shortend something internal got out of line? I was thinking maybe the exhaust tube did not get lined up and the engine could run as strong as before.

Nothing was out of line, I pulled it apart and everything was as it is supposed to be.

Did you have a jack plate for when you were running the longshaft?

No, ran it the same as it is now.

I dont see how you could have gone faster with a long shaft with that boat. You would have another 5 inches of lower unit in the water, which equals more drag. Most of the time a long shaft on a 15" transom can't even get on plane with that much drag.

Have you gotten a gps reading with the longshaft and the short?

I never had a GPS before I had it shortened. It runs about 17MPH now. It was a big noticable decrease in speed though. It was a better performing motor as a long shaft than a short. I don't understand it unless like metioned before that it was creating a different angle for leverage.