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Compression test on 40 hp. 98 RLEC.

Joe- "I assume you mean that the rpms decrease and increase without moving the throttle."

Yes that's what it does. It does it very suddenly, sort of like turning the switch on and off on and off on and off, over and over.
 
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Racerone- But yesterday it ran perfectly, and I do mean perfectly, for close to an hour before it started acting up, so I'm thinking my compression test was flawed.
 
joereeves said:
I may have asked previously but can't find a record of it............

This surging........ I assume you mean that the rpms decrease and increase without moving the throttle.

Is this a sharp, quick, sudden, instantaneous change of rpms (ignition)?.... OR

Is this a gradual, sort of smooth change of rpms (fuel)?
Click to expand...

"sharp, quick, sudden, instantaneous change of rpms", pretty much like turning the switch on for two seconds, then off for two seconds, then on then off, etc etc. So is the coil the most likely suspect in this case?
 
BigMuddy said:
"sharp, quick, sudden, instantaneous change of rpms", pretty much like turning the switch on for two seconds, then off for two seconds, then on then off, etc etc. So is the coil the most likely suspect in this case?
Click to expand...

Yes, that would indicate a ignition breakup OR something interfering with the ignition process.... which has me wondering about the possible compression problem which could simply be a failed head gasket allowing a slight water spray enter the cylinder(s) which would surely result in intermittent spark plug failure.

I'd suggest first (spark plugs removed) a spark test to see if the spark is a strong blue lightning like flame... a real SNAP!... for peace of mind if nothing else.

To check for a intermittent ignition switch short, simply remove the black/yellow wire (kill circuit) from the ignition switch. If that cures the problem, replace the switch. NOTE: with that wire disconnected, it will be impossible to kill the engine by turning the key to the OFF position.

If the problem persists, then I'd be removing that cylinder head to inspect the head gasket, piston dome, and block and head sealing surfaces.
 
What's been nagging at me is the fact that it ran so well immediately after cleaning the carbs for 40 minutes or so but then suddenly just fall apart. It just didn't make sense to me, and still doesn't, that if the engine was as weak as the compression test suggested that it could possibly run so well for so long. I may be dead wrong about that and I openly admit that my outboard motor knowledge is extremely limited. In fact that's one reason I was really hesitant to start pulling heads and such, pretty scary stuff to me. But anyway, I think I may know now why it ran so well for awhile and then suddenly fell on it's face. Here's what I found out this afternoon.

I went out to pull the carbs again so I could re-clean them and this time put the new kit parts in. But before beginning that job I decided to stick on the muffs and run her one more time in the driveway, just because. ....Anyway, it wouldn't even start, which is a first for that motor. Pulled the hood, and the first thing I see is gas dripping out of the air silencer.... So then I figure I definitely need to pull the carbs again and see what the heck's going on in there.

I pull the top carb and as soon as I start taking it apart I find the problem. Some dummy, yeah, that would be me, :rolleyes: had apparently forgot to tighten the float valve seat and it was loose as a goose and backed half way of it's hole. Stop laughing! So anyway, I went ahead and re-cleaned both carbs and installed the new kits, even remembered to tighten everything this time......... Put them back on the motor and she started right up and runs good on the muffs. Taking her for another test run in the morning. Wish me luck!
 
Yeah, I sort of figured that you were going to do some heavy duty double checking before you went looking for a bad head gasket.... glad that you found something even if you did look in the mirror and saw "Red Foreman" looking back at you, calling you names. :cool:
 
Took her back to the river this morning for another test run. Did an 8 mile round trip at various speeds ranging from a fast idle all the way to WOT and if she's ever ran better it was too long ago for me to remember it. Just wanted to thank everyone who shared their knowledge and expertise with me on this, with special thanks to Joe for sticking with me through the whole process. Thanks guys!
 
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