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97 200HP Johnson dies under load

J

jdhnc

New member
"Hi, I have a 1997 200HP Johns

"Hi, I have a 1997 200HP Johnson. It currently bogs down under load and dies. It will work correctly for brief periods of time and it doesn't happen at low RPM's with no load so I've never been able to replicate any symptoms in the driveway.

Due to previous problems (seemed to be fuel starved at WOT, but ran fine if the primer was pumped), I have replaced all of the fuel hoses, filters, fittings, primer, the VRO and had the carbs cleaned by a local shop. The new VRO and/or fuel fittings seem to have cured the original problem but now it dies under load. After installing the new VRO and hoses, I put it back in the water and it ran great for about 5 miles. I turned around and headed home and it started with the new symptoms.

The gas had been in there over the winter so I drained it all and refilled with fresh fuel.

Any suggestions on where to start? I already paid the shop $400 to clean the carbs, but that was before this problem cropped up. I have drained all of the fuel from the tank, put in a new water separator, a new inline filter and replaced the plugs. The plugs the dealer put in were Champions, but gapped around 0.020 if that. It really looked like they were just fresh out of the box. All six plugs were wet with some carbon buildup (looked like all had been firing at some point).

I will be checking the compression and spark in the driveway, but I have no way to replicate a real load unless I put it back in the water.
Any directions for additional diagnostics will be greatly appreciated.

Thanks,
John"
 
"This isn't the old "l

"This isn't the old "lean lockup" is it?
When a cylinder is running lean, it heats up, and the piston expands in the cylinder to the point of shutting down the motor from the piston to cylinder friction.

Here is the scenario: You are running at or near WOT...things seem OK, and then for no reason, engine dies as if the key were turned off.

Sometimes it will not turn over again until you wait a few minutes while that piston cools.

If that is what is happening, you need to do a compression check. It will tell you which cyl locked up on you. On that motor, you should see compressions around 110 to 90, and they should not vary across all 6 cyls by 10%.

Unfortunately, it is an expensive fix."
 
"I don't think so. It alwa

"I don't think so. It always turns over fine and it seems to run ok in neutral. It just dies when you try to accelerate with it in gear. I don't think it is the shift switch, but I will check it."
 
"I checked the compression. My

"I checked the compression. My gauge and method gave the following:
From the back:
Port Stbd
95 95
100 100
90 95
These are almost identical to what they were when I had the motor checked when I bought it 5 years ago.
Spark looked good on all six.
I drained all the carbs and removed the jets, nothing appeared to come out when flushing them.

I'm going to try to get it down to the boat ramp tomorrow, but I'm hesitant to take it out without a lot of daylight and little ramp traffic. The last two diagnostic outings have been pretty embarassing. Any reason I couldn't leave it on the trailer and put it under load while still at the ramp?

Anyone have any suggestions for what to try with it in the water? The only things that I've really changed are dumping the carbs and re-gapping the plugs. Would the .020 gapped plugs have caused this much trouble? Would it have caused intermittent problems?

John"
 
"Good compression.
Check that

"Good compression.
Check that the timer base if freely moving under the flywheel as you advance the throttle.
You can do that in the driveway, with the engine off.
No cost."
 
"ck to see if u have an anti s

"ck to see if u have an anti syphon valve,on the outlet to the engine,on,the fuel tank..if so,..knock out the ball and spring,or ,better replace,w/BRASS ,not aluminum straight fitting.."
 
No anti-siphon valve. I did ha

No anti-siphon valve. I did have a cut-off ball valve on the tank outlet but I removed that a few weeks ago and replaced it with a straight brass fitting.

John
 
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