Johnson 9.9 loosing power

[KMixson]

Once again, I am in awe of the expert, free diagnostic analysis that Pappy gives so generously.

We're pretty lucky here, folks.


=D> =D> =D> =D>

I would upvote this comment, but I don't know how.

 

[GYPSY400]

The pin hole is there on purpose.

After taking a good look I would agree, it looked drilled rather than worn through.

I'll be getting this motor out on the water soon, it's almost back together.

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[GYPSY400]

Ok, I know it's been a long time, but I finally had a chance to get this motor back together! Too busy fixing everyone else's stuff..
so I'm running it on the test tank and it's not running nearly as good as it did last year. Did some small tweaks to the timing and carb , but still would not run perfect. Got the temp gun out and check the head temp as one was hot to the touch, and one not so bad. Holy Smokes!! 100°F differential between the two and the top cylinder is getting really hot! I think I was at like 180 when I shut it off. Remember, new thermostat, and water pump when I did the head gasket to rule out cooling system issues.
Took apart the thermostat to see if maybe a piece of debriss got caught in it, found that the copper slug came apart - there is like a little nipple in the top and I don't recall it being a separate piece. But now it is.
Reassembled it without the thermostat , engine runs at a decent temp, with maybe 10° different between cylinders. Got it out to camp , motor ran like a champ at all engine speeds.

I might get ambitious over next winter and put another thermostat In it.

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[Pappy]

Thermostat is there to control idle temps only. Does not come into play much above idle. There are two pressure reliefs that pop off their seats to supply the volume it takes at higher speeds.
If you did not replace the rubber diverters you will most likely continue to have cooling issues.

 

[GYPSY400]

Thermostat is there to control idle temps only. Does not come into play much above idle. There are two pressure reliefs that pop off their seats to supply the volume it takes at higher speeds.
If you did not replace the rubber diverters you will most likely continue to have cooling issues.

I removed items 19 and 33 only. I left the other plastic parts in the housing to try and somewhat restrict the coolant flow. Are the rubber diverters you speak of items 41,43?

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[Pappy]

Ignore my comment about the diverters. Was thinking another engine at the time I wrote it.
The complete assembly pops off the rubber seat once rpm comes up and water pressure increases. This gives the volume of cooling water needed to cool the engine at high load and speed. The spring keeps it on it's seat at idle and off idle and the thermostat expands and contracts and controls temp for good idle quality and transition.

 

[GYPSY400]

Ahh ok, good to know. I'm going to run this motor as is without the thermostat. If I gives me trouble trolling I'll put in a new one next winter. This motor is going to my hunt camp so it only runs 5-6 weekends a year, a few in the summer, and a few in the fall. The main objective is that it must run when hauling gear as it's about an hour if you have to row.

Thank you all for the help. Overheating would have been the last thing I checked after running down the rabbit hole of ignition issues.

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