Compression Inadequacy or ...?

[ksfowler27]

Hi everyone. I was hoping someone could shed some light on this for me. I was given a 1973 9.5hp johnson and the first thing i did was run a compression check on it to see if it was adequate, and by adequate i mean anywhere from 80 to 125psi. I know that is a wide gap but have gotten a pretty wide answer range for these so kinda just stuck with that as a base. Well i ended up with 40 on both cylinders which my gut is telling me is extremely low, but i'm now where close to novice when it comes to outboards so here i am. It fires up and runs mid to wot fine for about 5 minutes and almost always dies when brought to idle. So am i just turning circles or do you think i should just put it to bed. Thanks in advance! Ksfowler27

 

[ondarvr]

Compresion gauges can read very differently from one another, so getting a low reading isn't always bad news. But if you know this gauge well and trust it, you may have issues.

Head gasket could be bad, or you can hope it is.

Low compression can cause hard starting and poor running at low RPMs, but so can a dirty carb.

 

[boobie]

Just for the heck of it, try another gauge. And then do a good de-carb on it.

 

[Grub54891]

If it was sitting for awhile before ya got it, yeah, it is probably gummed up/sticky rings= a good de-carb and carb kit just may help quite a bit.

 

[oldboat1]

If it was sitting for awhile before ya got it, yeah, it is probably gummed up/sticky rings= a good de-carb and carb kit just may help quite a bit.

recommend in that order, if you are going to do a decarb. Don't forget a water pump.

 

[ksfowler27]

Sorry i should have included that i did clean the snot out of the carb as was told and read that these engines are a bit particular to squeaky clean carbs to function properly, and i did double check with a different gauge and reading was fairly similar. I just wasn't sure if low compression would allow one pull starts and no low idle function. Again thanks for the quick responses and all the help. ksfowler27

 

[RCO]

The compression on those 9.5's is pretty low- I would expect to see 60-70 pounds on a perfect running motor. Decarbon wouldn't hurt, carb kit would be most likely. Pay close attention to the slow speed circuit in the carb.

 

[scout-j-m]

I have an earlier model with 65 psi on each cylinder and it runs really well at WOT. Pushes my 1648 flat bottom 15 mph at about 4700 rpms with two people, gas, battery, TM, and fishing gear. But mine also is not the best at low speeds despite a very thorough carb cleaning and points adjustment. I say that to point out the thing I have not tried yet which is to replace the upper crankshaft seal. May be something you want to look at. You can check it and replace it pretty easily from my understanding. I'd do a decarb then maybe look into this.

 

[ksfowler27]

Would it hurt possibly to spray some pb blast in the cylinders or atf to free up some of the carbon build up and possibly increase the pressure? Also when I looked at the coils they had hair line cracks on them. Still seem to give off good blue spark, but one tends to get a good shock if your touching the motor when pull starting.

 

[Grub54891]

Well, if you are getting a shock from touching the motor, the spark is going places it should not go. Change the coils!

 

[Bosunsmate]

Would it hurt possibly to spray some pb blast in the cylinders or atf to free up some of the carbon build up and possibly increase the pressure? Also when I looked at the coils they had hair line cracks on them. Still seem to give off good blue spark, but one tends to get a good shock if your touching the motor when pull starting.

not sure how it might affect the lower seal when it drips down on to that, to be cautious i wouldnt

 

[ksfowler27]

Ok got it guys. Will do and report back with results. Thanks, ksfowler27

 

[lindy46]

Well, if you are getting a shock from touching the motor, the spark is going places it should not go. Change the coils!

May be a bad plug wire - did you change them? I'd get some Seafoam (liquid) mixed with the gas and get a can of Seafoam Deep Creep to spray into the carb throat when the motor is running.

 

[ksfowler27]

No Title

Thanks lindy46 for the great info. I did check the spark plug wires thoroughly and found no issues with them. Also did a resistance check on them and 0.00. So the coils had spider cracks all over them so I'm sure that's the issue but won't be 100% until I get the new ones on tomorrow. I did however get the new points w/ bases and new condensers today and when I went to time and set points I wasn't getting a ground for the new bases. Whether the point is open or closed it stays at a constant 1 ohm. I did not have this issue with the old bases. I've included pics of the new and original base. Thanks for all the help guys!

 

[ksfowler27]

Also I forgot to mention that I have a suspetion that my fuel bulb is an issue even though it's brand new. It will only prime if the fuel bulb is perfectly up and down and if it tips even just a bit I here a gergaling and then the bulb is soft again. Is that normal?

 

[ondarvr]

Also I forgot to mention that I have a suspetion that my fuel bulb is an issue even though it's brand new. It will only prime if the fuel bulb is perfectly up and down and if it tips even just a bit I here a gergaling and then the bulb is soft again. Is that normal?

They are designed to work vertically, but shouldn't be that sensitive, bulbs are frequently bad when new.

 

[racerone]

Love the creative spelling.

 

[ksfowler27]

Any thoughts on the new point bases no grounding? Not sure if they are suppose to or not but can't get a reading off of them.