Can I improve proformance by replacing the original prop? (73' Evinrude 9.5)

[eoitker]

I have a 1973 Evinrude 9.5 Sportwin with the original prop on it. The prop is in great shape but I am curious if I can increase the proformance of the motor by changing it to a different prop and if so, what should I look for?

 

[steelespike]

Re: Can I improve proformance by replacing the original prop? (73' Evinrude 9.5)

Look for the prop size near the base of the blades or on the hub.
We will need to know what it is on and the wot gps speed lightly loaded.
Would be best to have a tach.An induction tach will work.

 

[steelespike]

Re: Can I improve proformance by replacing the original prop? (73' Evinrude 9.5)

The ability to "improve performance" would depend on your setup , your present numbers and what you want to improve.
The 9.5 could make about 20 mph on a light reasonably fast boat.

 

[eoitker]

Re: Can I improve proformance by replacing the original prop? (73' Evinrude 9.5)

Ok, I'll get the numbers off of the prop and post them back here. The motor is on a small Ouachita Jon boat 14' x 36". Allways lightly loaded with a small cooler, fishing tackle and the trolling motoer with battery. The battery is installed bow to offset my big butt in the back!

 

[steelespike]

Re: Can I improve proformance by replacing the original prop? (73' Evinrude 9.5)

You may be surprised; I think your weight is probably close to 400 lbs if you count stuff like anchors ,oars
gas and tank,fishing gear,motor 60 lbs, 200 lbs for you etc.
i'm thinking the capacity is probably around 500lbs so I'd call it a heavy load.
No mater we'll get it figured out.
Describe your performance.

 

[eoitker]

Re: Can I improve proformance by replacing the original prop? (73' Evinrude 9.5)



Steelespike,
Thanks for your replies! You are right, my rig is probably heavier than I think. The only markings I found on the prop was the word Michigan, something that looks lile P I and 10. I hope to get the GPS speed this weekend but what is WOT? I have a Dwell tachometer but it states it is for 4 cylinders or more. I have only had it on the water once since I rebuilt it and I would say the performance is average. I was just curious if I could gain any performance from a different prop and if I did, would it be worth the cost?
Thanks

 

[jimmbo]

Re: Can I improve proformance by replacing the original prop? (73' Evinrude 9.5)

the stock prop was plastic and probably an 8 1/8 x 8. That was taken from a 1972 brouchure. It is unlikely to have changed for 1973. They also offered an 8 x 7 aluminiun as well

 

[steelespike]

Re: Can I improve proformance by replacing the original prop? (73' Evinrude 9.5)

View attachment 209126

Steelespike,
Thanks for your replies! You are right, my rig is probably heavier than I think. The only markings I found on the prop was the word Michigan, something that looks lile P I and 10. I hope to get the GPS speed this weekend but what is WOT? I have a Dwell tachometer but it states it is for 4 cylinders or more. I have only had it on the water once since I rebuilt it and I would say the performance is

average. I was just curious if I could gain any performance from a different prop and if I did, would it be worth the cost?
Thanks

WOT = wide open throttle.
For now lets shoot for wot gps speed. If you contact Michigan Wheel with the year of your motor and the numbers on the prop they should get back to you with prop info. I can find your gear Ratio.
You may be able to improve performance but don't expect brilliant numbers.It will be things like a little faster with a load maybe a touch more speed,maybe able to plane with a load when you couldn't before.
It all depends on the present prop size and your results.

 

[eoitker]

Re: Can I improve proformance by replacing the original prop? (73' Evinrude 9.5)

ok, I'll contact Michigan Wheel. Maybe this will help until I get back on the water. The last time I was on the water with the motor, I had it on my brother in laws lightly loaded (no gear) 16' x 5' flat bottom Jon. (just like mine but bigger and heavier) We got a WOT GPS speed of just over 8 mph. I have a pretty cool video that I can post if it will help.

 

[steelespike]

Re: Can I improve proformance by replacing the original prop? (73' Evinrude 9.5)

If its a bare bones 16,no floors live wells etc. assuming you guys are not 300 lbs each I think you should be making 15-18 mph.
Its even possible the big boat could be as fast or faster than your little boat because it can get up on the water easier with that big foot print.
If your at only 8 mph you have some sort of problem. I would start by checking if it is running on both cylinders.
at 8 mph you wouldn't be planed.Unhook one plug at a time and see if it runs.
Coil failure is really common with the omc motors with those magnetos around that time.
You wouldn't be the first to not realize you were on one cylinder but for the lack of power.
A video might give us a clue.