# New to me 1969 johnson 9.5hp seahorse



## AppalachianAmerican (Jun 22, 2015)

This past week i bought a 1969 9.5hp Johnson short shaft for my 14 ft alumacraft shallow v hull. I ran it this weekend, and seems to run pretty good, but want idle well at low speed. I would say it was pushing the boat maybe 6 to 8 mph with 2 people and fishing gear and 3 gals of gas. Seems a little slow to me...am I wrong? The transom on my boat is pretty short, and the cavitation plate is about 3 to 4 inches lower than the bottom of boat , I think I may need a jack plate and a carb cleaning.It has new plugs and wire, looked good when i checked them, has new fuel pump and water pump and had a carb kit and tune last fall, but hasn't been run but once this year before I bought it. What are your thoughts? I think this motor should push this boat more like 10 to 12 mph.


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## ggoldy (Jun 22, 2015)

Off the top of my head:
1. Both cylinders firing? Sometimes it's hard to tell.
2. Low compression would cause bad idling.
3. You're right. Carb rebuild is always a good thing for an old, unknown motor.....as well as a new impeller.


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## AppalachianAmerican (Jun 22, 2015)

I'm am afraid it might be running off one cylinder. I checked the plugs and they both looked to be getting fire, but yea the compression could be low. looks like i'm going to need to take it for a servicing. But that motor running right should push that boat pretty well right?


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## ggoldy (Jun 22, 2015)

A compression tester and spark tester are handy. They can't be very expensive as I have both and I'm extremely cheap  They are most helpful when buying a used OB. Will tell you a lot about the motor.
I 'think' you should get better speed but, I'm not knowledgeable enough to be sure. Many variables.


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## CMOS (Jun 22, 2015)

AA,

I have a 1966 Johnson 9.5 on a 14' flat bottom V. Runs about 14 MPH with a full tank of gas, myself, the wife, and 45 lb daughter. So yes, you should see at least 10-12 MPH IMO.

Go through the checklist of things to check . . .

CMOS


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## AppalachianAmerican (Jun 22, 2015)

here's the motor, it's in pretty good shape cosmetically, I do think this the motor is sitting to low, that cav plate is a good 3 to 4 inch below were i think it should be..thoughts?


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## CMOS (Jun 22, 2015)

In general - the anti-vent plate should be _even with, or slightly below the water surface while up on plane.
_

There is a generalization that you will hear regarding the placement of the anti-vent plate being "even with" or "slightly above the hull bottom" but the more precise placement is the above statement. Yours definitely sounds like it's too low.

A very cost effective solution is to buy a Mini Jacker plate (less than $100).

CMOS




AppalachianAmerican said:


> here's the motor, it's in pretty good shape cosmetically, I do think this the motor is sitting to low, that cav plate is a good 3 to 4 inch below were i think it should be..thoughts?


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## AppalachianAmerican (Jun 29, 2015)

My transom measured 15 inches, same as my outboard. However do to the angle of the transom, measuring straight down is only 12 inches. I plan on making a wooden shim to raise the motor 2 to 3 inches and see if that makes any difference before building a jack plate. A good friend of mine is giving the ole 9.5 a good tune up. Cleaning carb, checking compression, new plugs, checking fire, cleaning fuel filter, and changing lower gear oil. hopefully this all results in a good idle, and strong running outboard pushing my hull a good 12 to 15 mph


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## CMOS (Jun 29, 2015)

AA,

Before you rule out the Mini-Jacker plate, check something on your transom: If you "lift" up your motor the 2-3" mentioned, will the motor clamps still grab the transom, or will be be above the transom top altogether?

I need to raise my motor up probably a full 2 inches but could not do so for the above reason. I had to settle, for now, with just shimming it with a short piece of 1x2 board, which only raised it 3/4". At this point I'm not going to mess with it as it performs okay for me. However, when I get the new (to me) 15 HP running I may invest on that Mini-jacker plate system.

CMOS


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## AppalachianAmerican (Jun 30, 2015)

your right on the money, I've checked all that, and they just grab the top part of the transom. little to high for my liking but it clamps and seems to hold enough to test.


Question? whats the normal compression for this motor? I tested mine and its 60 psi both cylinders...seems low


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## CMOS (Jun 30, 2015)

Oddly enough that is a concern for mine - which is 70/70. Even that seems low to me. Trying to get an answer from some of the more knowledgeable guys here on those numbers.


CMOS


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## AppalachianAmerican (Jul 2, 2015)

I think i'll do a decarb with seafoam, and check compression again


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## CMOS (Jul 2, 2015)

AA,

More info:

I have been emailing back and forth with LeeRoy at "LeeRoy's Ramblings" and he had some things to say about the compression on these year models (1965-1970).

I quote:

*"Those motors that use the old spool type starter, are known for low compression, simply because the spool turns it so slow in relationship to the flywheel. To get a reasonable compression test you have to pull on the rope like you are MAD at it. And those testers are known to not produce equal pressures. The numbers seem low for all other motors, but not really for yours. Try it again but pulling harder & faster, I will bet it raises the compression. Better yet, try it with a emergency rope around the flywheel & let me know if that raises it."*

I wonder if we could rotate the flywheel nut with an impact wrench to do the compression test (both plugs pulled of course)?

Taking her out on the lake tomorrow. Can't wait. There's a BBQ place right on the lake called "Uncle Bob's BBQ" that's worth the trip alone. We eat lunch first, then set sail.

Let me know if any progress you make.

CMOS


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## AppalachianAmerican (Jul 3, 2015)

I pulled the plugs, gave a shot of seafoam and let it sit. Checked the compression in both cylinders at the end of the day, top cylinder at 65psi and bottom at 70 psi. Now i need to get it on some water and run it.


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## CMOS (Jul 3, 2015)

AppalachianAmerican said:


> I pulled the plugs, gave a shot of seafoam and let it sit. Checked the compression in both cylinders at the end of the day, top cylinder at 65psi and bottom at 70 psi. Now i need to get it on some water and run it.




Where did you put the SF???



CMOS


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## AppalachianAmerican (Jul 3, 2015)

i sprayed the seafoam into the sparkplug holes, let it sit, sprayed again, let it sit.


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