1971 John 9.5hp...30lbs compression what needs to be replaced?

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wolfgang123

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Okay guys so i bought this motor on ebay and the tiller handle was damaged in shipping. I unbolted the stock tiller and replaced with a 1966 tiller handle. The red indicator dot for the throttle position seems to be a little off as far as matching up with the "slow" "Shift" "fast" written on the handle but the carb butterfly opens and closes all the way so i am assuming its no big deal. Is there any way i messed up the timing doing this? Other than that i see low compression being the problem behind my motors lack of top end power, she runs great and idles pretty good but has no top end. The only thing i have checked at this point is the compression, tomorrow i will check the points and make sure they are right, and make sure its running on both cylinders. But unless my compression tester is crazy i figure thats the problem.

So what do i need to get for a rebuild?
 
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Rick.

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Re: 1971 John 9.5hp...30lbs compression what needs to be replaced?

The first thing I would replace is your compression tester! They can be so inaccurate. So here is how I check compression. Both plugs removed, test the top hole first. Keep pulling and counting pulls until the gauge stops increasing in numbers. Write down the highest reading you got to. Put gauge on lower and pull the exact number of pulls and read the gauge. write it down. I would expect the readings to be 60 or better and within 10%of each other. Report what you have written down back here. I do hope a second gauge gives higher numbers. Pay little attention to the tiller handle position. They get loose with wear and time. The fact that it starts is a good thing as if compression were too low it wouldn't. No top end is often a dirty high speed circuit in the carb. Take the hood off and run it as 9.5'5 often develop exhaust leaks and are sucking in bad air. Best of luck. Rick.
 
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wolfgang123

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Re: 1971 John 9.5hp...30lbs compression what needs to be replaced?

Okay well i just got back from pulling the spark plugs to see if both cylinders where operating and its kinda wierd. It runs but significantly rough with the bottom cylinder unpluged. It runs much better but still not perfect with the top cylinder unpluged.

So does this irregulatrity mean its an iginition componet problem?

Tomorrow i will get another pressure tester and try again. but i think the compression might actually be this low.
 
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wolfgang123

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Re: 1971 John 9.5hp...30lbs compression what needs to be replaced?

Rick. said:
The first thing I would replace is your compression tester! They can be so inaccurate. So here is how I check compression. Both plugs removed, test the top hole first. Keep pulling and counting pulls until the gauge stops increasing in numbers. Write down the highest reading you got to. Put gauge on lower and pull the exact number of pulls and read the gauge. write it down. I would expect the readings to be 60 or better and within 10%of each other. Report what you have written down back here. I do hope a second gauge gives higher numbers. Pay little attention to the tiller handle position. They get loose with wear and time. The fact that it starts is a good thing as if compression were too low it wouldn't. No top end is often a dirty high speed circuit in the carb. Take the hood off and run it as 9.5'5 often develop exhaust leaks and are sucking in bad air. Best of luck. Rick.
Click to expand...

I have tried running with hood off no difference. Previous owner said they did a carb kit but at this point i dont know if i trust them so maybe a carb kit? or just a cleaning? i will look in my manual for info on the high speed circuit in the carb
 
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bonzoscott

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Re: 1971 John 9.5hp...30lbs compression what needs to be replaced?

I have a '73 9.5 and it's a tough motor. If you had it running, I doubt that compression is as low as 30lbs. I would first try the points. File them a little with a points file and check for strong blue spark. If that doesn't happen, replace the points - about $17 Napa - and set at .020 Spray some Sea foam in the cylinders and compression will improve!
Believe it or not - Grandpa bought motor new in '73 and I've done nothing to it except lower unit oil. Starts 2nd pull in March every year.
 
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wolfgang123

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Re: 1971 John 9.5hp...30lbs compression what needs to be replaced?

Alright i will seafoam in the morning for sure!!! The points do have me a little confused, am i measuring the gap between the crankshaft and point or where the 2 circle metal tabs are on each "point arm"...ahh sorry i hope all that makes sence.
 
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wolfgang123

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Re: 1971 John 9.5hp...30lbs compression what needs to be replaced?

OKay so i sanded and reset the points to .20 and picked up a gap tester from pepboys...The spark jumps a 1/4'' gap about 50 percent of the time. new head gasket should be here tomorrow and i will seafoam before i install that.
 
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Rick.

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Re: 1971 John 9.5hp...30lbs compression what needs to be replaced?

50% of the time on both cylinders or on one cylinder only? Try to be more specific if you can. The spark tester needs a good ground for the test to work properly. If it's bad on one only you can start moving parts around to help figure out what is bad but if they are both giving problems then that method isn't an option for you. Would strongly suggest resurfacing the head prior to installing a new gasket. They are often a little out. Rick.
 
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wolfgang123

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Re: 1971 John 9.5hp...30lbs compression what needs to be replaced?

Yes both top and bottom cylinders seem to have a weak spark. So should i replace the coils? or wait and figure out the compression issue before dumping money into the ignition?
 
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Daviet

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Re: 1971 John 9.5hp...30lbs compression what needs to be replaced?

The spark needs to be bright blue and jump a 1/4" air gap and be constant. If it doesn't you could have a coil or points problem.
If the engine will run, I would think the compression would be good enough to invest a little money in the engine.
 
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Rick.

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Re: 1971 John 9.5hp...30lbs compression what needs to be replaced?

I just makes me think your compression is better than reported. Once you get the new head gasket on try to borrow a different gauge. Perhaps Pepboys would lend you one. I cannot see it running with poor spark on one cylinder with only 30lbs of compression. How do your coils look? I bought a 5-5 on the weekend and could not get spark to jump 1/8 inch. Pulled the flywheel and saw two of the worst coils I've seen with a new set of points LOL. Funny thing was as bad as they looked I was getting spark to the fingers when I held the wire near the boot. So even those horrible looking coils were giving some spark. If yours look bad they should be changed but compression first. I never am very willing to spend money on a motor until I'm convinced the compression is good. Once that checks out then I'm more than willing to spend whatever to get it running consistently well. Can't wait to here your numbers as I think they are going to be much higher. Rick.
 
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wolfgang123

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Re: 1971 John 9.5hp...30lbs compression what needs to be replaced?

OKay well i sanded the point and reset them, seafoamed the motor and cycled a little bit through the carb into the cylinder to let it sit over night. Got another compression tester and still 30lbs :( (i fell like something is up about this). Anyway she runs 100 percent better, quicker faster revs (atleast while in neutral)

One problem though. when i WOT then turn her back it seems to take a while before slowing down? (i am thinking its just beacuse its in neutral and without the weight of the prop it takes a little longer to slow.

New head gasket should be on tomoroow i will report back then.

And the points and coils look to be in great almost new conidition. I will reset the spark with a better ground tomorrow and see if i can get it to jump.
 
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Rick.

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Re: 1971 John 9.5hp...30lbs compression what needs to be replaced?

Sounds like your making good progress. I had not so good compression numbers on my 4hp when I first got it. Did a seafoam and it really didn't burn any carbon much. A week later I redid my compression and it was 10 to 15 lbs. better so someone suggested it must have unstuck my rings. Rick.
 
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gozierdt

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Re: 1971 John 9.5hp...30lbs compression what needs to be replaced?

wolfgang123 said:
OKay well i sanded the point and reset them, seafoamed the motor and cycled a little bit through the carb into the cylinder to let it sit over night. Got another compression tester and still 30lbs :( (i fell like something is up about this). Anyway she runs 100 percent better, quicker faster revs (atleast while in neutral)

One problem though. when i WOT then turn her back it seems to take a while before slowing down? (i am thinking its just beacuse its in neutral and without the weight of the prop it takes a little longer to slow.

New head gasket should be on tomoroow i will report back then.

And the points and coils look to be in great almost new conidition. I will reset the spark with a better ground tomorrow and see if i can get it to jump.
Click to expand...

DON'T run WOT in neutral or anytime on muffs. The engine can go way over normal rpm range with no load. Bad news!!

I suspect you may have stuck rings, as suggested. It just seems to be running too well to have only 30 psi compression. If it turns out that it is that low, and nothing else works, you'll need to tear down the powerhead and measure the cylinders and pistons to see what's worn. If the rings and pistons are scored, but not the cylinder walls, and the cylinders aren't too badly worn, you might get away with just replacing the rings.
 
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wolfgang123

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Re: 1971 John 9.5hp...30lbs compression what needs to be replaced?

Alright so after like 7 sheets of sand paper I finally got the head resurfaced and the new head gasket installed. I ran a ton of sea foam through the motor and while I had the head off I used some sea foam deep creek while slightly tapping on the pistons while I rotated the motor via flywheel to help free the stuck rings (defiantly stuck rings the piston and cylinder walls looked great!!!) I got out on the water and she idles SOOOO much lower and smooth and I actually got my 8 foot boat up on a plane!! Everything was good I figured I had freed the stuck rings......then after a small break I started her up to go home and now I am back to no power at full throttle right where I started (but it still idles much lower and smoother). I got home and checked the compression still at 30lbs (WTF!!!). Here is the weird part, I can actually feel that the motor has more compression when I turn it over it was literally noticeable but the compression gauge shows no change.

So did the rings get re-stuck?

Also while I was able to get her up to plane the acceleration was terrible and took for ever to reach top speed.

So I have no idea what to do at this point, tonight I will try a rope on the fly wheel to try to get better compression numbers, will report back tonight.
 
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Rick.

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Re: 1971 John 9.5hp...30lbs compression what needs to be replaced?

Sure sounds like you high speed circuit is dirty. I mentioned it some time ago. That would be my thing to do now. Is there any chance you not getting a good seal with your compression gauge? Rick.
 
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