1967 Johnson 9.5 bogging down at wot

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dockrat100

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I recently took a new a newly acquired 1967 9.5 Johnson out for a spin, and found that it bogged down if I twisted the throttle too far. It runs like a top to a point, but if I go too far, it bogs down and nearly stalls. I cannot see any difference in the throttle plate from where it runs good and where it bogs down.
Any ideas?
 
HighTrim

HighTrim

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Re: 1967 Johnson 9.5 bogging down at wot

Have you cleaned/rebuilt the carb?
 
kbait

kbait

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Re: 1967 Johnson 9.5 bogging down at wot

They'll act like that if there's an exhaust leak under the cowl. Run w/cowling off to confirm.

Good luck!
 
ultra353

ultra353

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Re: 1967 Johnson 9.5 bogging down at wot

Sounds like your high speed jet is clogged.
 
D

dockrat100

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Re: 1967 Johnson 9.5 bogging down at wot

I did clean the carb, and put a new valve and seat in it. Seems to run great, except for the problem described above.

It may indeed have an exhaust leak, seems like I had some exhaust come out of the cowl when I removed it, but where should I look to address that?
 
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jbowser

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Re: 1967 Johnson 9.5 bogging down at wot

My brother had a similar broblem this past season. His leak was in the rubber exhaust boot leaving the cowling. I am not familiar with your engine, but maybe that's where your leak is.
 
D

dockrat100

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Re: 1967 Johnson 9.5 bogging down at wot

The rubber exhaust boot is intact.

I did pull the carb and checked the high speed jet, and it is clear. I shot some carb cleaner in the hole, and some dribbled out a small hole near the top of the carb, near the air intake. Is that normal? it looks like that hole maybe should have a shot in it.
 
jbjennings

jbjennings

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Re: 1967 Johnson 9.5 bogging down at wot

Instructions repeated: take the cowl off and run it to confirm exhaust leak. The 9.5's are notorious for them. There's more than one place for exhaust to leak on those.
If not that, then possibly a link-n-synch would be in order. Is the throttle plate opening fully along with full spark advance?
GOod luck,
JBJ
 
D

dockrat100

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Re: 1967 Johnson 9.5 bogging down at wot

I have not been able to run the motor today, as I got stuck, er, was given the privilege of supervising my daughter. I will run it in a barrel tomorrow.

Forgive my ignorance, but by running it with the cowl off, am I looking for the exhaust leak, or does the additional ventilation negate the negative affect of the exhaust leak, or both?

Regarding the link and sync, The throttle plate is all the way open with timing fully advanced. (As far as I can tell) I will double check that tomorrow when I run it.

Thanks, Jason
 
HighTrim

HighTrim

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Re: 1967 Johnson 9.5 bogging down at wot

Running it on a boat with the cowl off will cause the exhaust to be blown away, negating the leak as you stated. Easy quick way to troubleshoot the problem is all.
 
TN-25

TN-25

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Re: 1967 Johnson 9.5 bogging down at wot

What plugs are you running? If they are a "hot" plug designed to burn off deposits while trolling or operating at slow speed, they can cause problems such as you describe at full throttle due to detonation. Do you get a "bag of marbles" sound while at full throttle? That is a sure sign of detonation, and it can wreck pistons. Check your plugs. Check the gap and also post what plugs they are.
 
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dockrat100

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Re: 1967 Johnson 9.5 bogging down at wot

Plugs are Champion J6C, gapped to .030. They looked good when pulled.
 
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dockrat100

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Re: 1967 Johnson 9.5 bogging down at wot

I ran the motor in a barrel, but will have to settle for inconclusive results for now. I can't really run the motor at wot in the barrel, but I will say that between running it with the cover on and off, it ran better with the cover off. It also seemed to have exhaust fumes coming from somewhere around the engine, but I could not tell from where. Where should I look? Is there a weak link somewhere in the system that is a typical failure?

I need to pull the housing off this engine anyway to replace some worn motor mounts, should the exhaust leak be addressed at the same time?
 
kbait

kbait

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Re: 1967 Johnson 9.5 bogging down at wot

There is a rubber shift-shaft seal just below the powerhead. If that is split, you will get exhaust under cowl, and into carb, choking it for oxygen. search boats dot net. ********** probably is *******'d. You can look up your motor and schematics there..
 
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dockrat100

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TN-25

TN-25

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Re: 1967 Johnson 9.5 bogging down at wot

dockrat100 said:
Sorry, page 10, number 87? Is that the seal you were referring to?

http://www.marineengine.com/parts/v...ntage-evinrude-johnson/382086/38208600001.htm
Click to expand...
I'll jump in here. Yes.

I have the very same motor as you, a 1967 MQ-13. They work very well, are compact & light, and have the easiest carbs in the world to get at. They are also a huge pain to replace the impeller on since you have so much disassembly & reassembly ahead of you. Not a problem since you need to tear it down to replace that gearcase seal anyway. I have piloted quite a few over the years. I caught my first fish from dad's cartopper with a then new 1965 9?. I just haven't really worked on one yet. Soon though...

Your plugs and gap sound like they are not the problem.


Good luck!
 
kbait

kbait

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Re: 1967 Johnson 9.5 bogging down at wot

I was referring to #78 on pg. 10. # 87 would cause the same issue, but usually that one is intact. You'll find out when you pull it apart. Good luck!
 
D

dockrat100

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Re: 1967 Johnson 9.5 bogging down at wot

Kbait, you were correct. The #78 shift rod boot was in two pieces. the rubber boot section had fallen down the rod allowing, I suppose, exhaust gases to escape. The big #87 seal was in there cockeyed, and I think it may have also been at fault.

While I was in there, I found that the front top motor mount was in two pieces. So that will have to be replaced as well. The powerhead was able to move around in the housing and battered it pretty badly.The housing has a crack that will need welded.
boat 004.jpgboat 009.jpgboat 007.jpgboat 008.jpgboat 012.jpg
 
TN-25

TN-25

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Re: 1967 Johnson 9.5 bogging down at wot

I seem to recall that motor mounts were a part that were subjected to revision on these motors. If I remember correctly, the 1964-65 models had some vibrations, causing OMC to revise the motor mounts for 1966. Dad had a 1965 that had a special Vibration Isolation Kit installed at the dealer later during service. There were 4 acorn nuts, 2 per side that were visible on the foreward part of each half of the lower cover assembly. They in turn were attached to some metal brackets inside the housing that served as additional mounts for the powerhead. Those acorn nuts were not present on any production motors, including the later models with revised motor mounts. With this retrofit kit I must say that his was the smoothest running 9? I have personally experienced. It is too bad that I don't have any pictures of those parts as installed in dad's old motor.

I guess that comparing part #s on a year by year basis can give evidence of revisions.

Dockrat, thanks for posting the pictures. It looks like I will have some fun when I get to my MQ-13.

P.S., I do have a 1967 Parts Manual for your motor. Although I have not gone through every part to compare with the 1968+ online parts diagrams available at the BRP Shop Evinrude site, it appears that the fuel pump and a few carburator parts are different. There is an online 1967 Parts Manual here: www (dot) marineengine (dot) com.
 
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