1972 9.5 hp prop options

[goof008]

I have a 9.5hp Johnson pin drive with a 8 1.8 x 8 3-blade prop on it. It's on a 14' fishing boat and I don't think it's getting full RPM at WOT. I don't expect to get a lot of speed out of it, but I thought 6mph was a little slow. Do props exist that are a smaller pitch or would a 2 blade option be best?

Any help would be great!

Thanks,
JC

 

[flyingscott]

Have you checked to make sure it is running on both cylinders? Have you tried running it with the hood off? Doesnt sound like a prop problem A 14' boat should be faster than that even with a 9.5.

 

[jimmbo]

Your engines WOT rpm range is 4000 - 5000. You really need a portable inductive tach so you will know how fast it spinning
The factory prop should still be in that range, probably the lower half on a 14 ft car topper.
iboats does show props for that engine as low in pitch as 6 1/2". But the only way know how fast it turning is with a tach

 

[F_R]

6 MPH??? Either your boat is a dog (or overloaded) or there is something wrong with that motor. A prop won't cure either problem.

 

[goof008]

The boat is an early 70's Lund 14 footer with a stern mount trolling motor, battery and a brand new plastic 6 gallon gas tank. A few other odds and ends, but nothing major. And 400 lbs in passengers.
It rev's higher in reverse than in forward.
I do have a portable tach I can throw on it.
the motor starts right up, idles great and runs great...just not fast. Figured it was a prop issue.

 

[racerone]

Make sure it is running on both cylinders.------Start it and pull one plug wire off at a time.

 

[F_R]

I have a 14" Lund also. Mine runs 35MPH. Of course that is with a 35hp on it.

 

[goof008]

ok, I checked the MAX RPM at WOT and I got 3400. The motor runs great and there is no sign there is an issue (no hesitations or sputtering or anything) it just won't rev high. Would that be a prop or possibly a clogged high speed jet?

 

[Crosbyman]

compression numbers available ??

 

[TN-25]

I would expect 15 to 20+ mph. Dad had a 14' aluminum cartopper (Nalco 14L) with a 9½. The boat was was rated for 15 horses and it ran about 20 mph with the 9½.

Props for the 9½ are shared with the old 10-horse 1958-63. Some years back in the 1970s you could only get a plastic (Lexan) prop but then they reverted back to aluminum.

You need to make sure both plugs are firing, compression is o.k. and that a link-and-sync are confirmed. There weren't many choices for props on those motors. The boat you are running the motor on sounds reasonable in terms of pairing.