Leaking crankcase leads to overheat condition?

[johnyrude200]

I pulled them out yesterday evening (the J6’s). They had white blisters on the electrodes. This morning I put new J6’s in and ran at 5500 rpm in the test tank with a test wheel for 5 mins straight closely monitoring with a heat gun. It was doing the same thing as when I had it on the boat yesterday. So I switched to J4’s and that seems to have corrected things.

My only hesitation is the fact that I pulled the thermostat and it is running fine, but again, there are no clogs I could find in the cooling system anywhere. This thing is pumping a ton of water.

I don’t think the thermostat is/was the issue, because the cylinder head and thermostat orifice never even reached 143° (opening point of the t-stat). The cylinders were getting hot (170°-ish) but only at sustained WOT. So my summation is that the plugs were too hot, and were the culprit.

[fleetwin]

Not sure I understand what you are describing with the starter interlock, can you post some pictures?
Again, you might want to go .001-.002" richer in the high speed jet just to be safe. The J4Cs will definitely run a little cooler.
And yes, I’m thinking you might be chasing a bit of a ghost, but it’s good you found the hot/lean WOT condition if the engine will be used continuously at WOT.

[johnyrude200]

Here’s a pic of the shifter which has passed the throttle stop on the mag plate. I looked a little more closely, and it seems as if I removed the shift gears on the outside starboard side, and placed a washer behind it, that would basically get everything lined up again and working properly. The motor is in neutral right now (not in the pic), but I can advance the throttle to WOT.

I wonder why this happens. Wear below the powerhead on the shifter linkage to the vertical gearcase linkage shaft?

[fleetwin]

I think I understand what you are describing. Sometimes those vertical detent/lockout rods get grooved where the mag plate stop hits them, allowing the mag plate stop to sneak by the vertical rod. Some of the newer engines have an actual roller on the shift handle where it rides on the vertical rod, but I don’t think yours came equipped that way.
Your idea about shimming the shift handle out with a SS washer would do the trick provided you can find a washer to fit in there. Just be careful removing that shift handle, the hardware might be rusted and the shift handle might break while trying to remove the screws.
So, don’t force the screws if they won’t come out, leave it the way it is. If the screws do come out, remember that you will have to readjust the shift handle to ensure proper dog engagement in gear.

[1946zephyr]

J6’s are fine to run in that motor. I’ve ran lot”s of 18’s with that plug. It’s actually better than the J4. If your crank case is leaking, you should find evidence of it, with fuel leaking out, while it’s running. I would definitely check your cooling system for restrictions. Make sure the passage all the way up to the power head is free too. If it’s a salt water motor, then they like to block up in the mid section, where the copper water tube goes in. I’ve found a few like that. A flex line like you would find on a lawn mower throttle cable is ideal for checking the water passage there. Once you check the water tube area, run it for a sec, with the thermostat out and the cover off. Water should come gushing out of there.

[johnyrude200]

Thanks for the advice Fleetwin. Will be careful with the shift lever removal and reinstall. To your point, the square washer is the one I’ve seen get stuck most times.

Zephyr – the cooling system on this motor is not the issue. I did a full tear down from the skeg to the manual starter, this is low-hour, fresh water motor, and it is the 1st 18-20-25 that I’ve seen run hot at WOT (and not super hot, but the situation predicates I split hairs since human life is in the balance based on motor performance, literally. There is no option for the motor to skip a beat when the moment calls for a 1/2 pull start and WOT 1 second later, without a single hesitation. It’s not what most motors were designed for [primarily father/son fishing trips], but it’s what the local town can afford on their budget so I’ll do what is necessary to make it fit the application).

The service manual calls for J4’s, it had J6’s (which I routinely put into my motors before they leave my hands), but in this instance, sustained WOT with no weird factors is causing it to run at 170° with a new thermostat and cause blisters on NOS J6’s, but not J4’s which are also J4’s (only after 2-3 mins of continuous WOT), impeller, clean impeller housing, no clogs or any evidence in any manner of water occlusions, new impeller grommet, etc.

It’s not a salt motor. This motor was aged, but in exceptional condition before I touched it. It was a 2-motor set up on a corson boat which I saved from the junkyard, and even before I put $400.00 worth of parts into it (retail), would have run reliably and been a workhorse. But when it comes to putting a motor onto an emergency vehicle, I’m going to take it an extra mile. The spark on this 1970 univeral magneto motor jumps 3/4 of an inch.

A tribute to all of the mentors/veteran mechanics of the AOMCI and the forums – as much as I appreciate CDi ignition – a fresh magneto throw spark in a competitive manner to the computer chips.

If I am just plain wrong in any aspect of this post, I have no problem being called out on it. Seriously.

[1946zephyr]

Well, good luck I hope you get things resolved. Keep us posted. 🙂

[billw]

Just a thought the regarding emergency use of an outboard….A lot of what I see around here, with our local fire departments and small, outboard-powered boats, is that they spend a lot of time idling, as they search or do their actual, physical rescuing. More often than not, it’s in colder water. You seem like a very thorough person. If I were you, and really wanted to use the J4Cs, I would do a LOT of long-term idle testing for fouling plugs, before I handed the motor over to the users. My two cents.

Long live American manufacturing!

[johnyrude200]

I think what Ill probably end up doing is supply them with a pair of J6’s and extra J4’s. I may recommend a weedless prop too. We’ll be bringing it out on the water in the next day or too and it’s a conversation we need to have. Its going on a very large fresh water body and 13′ whaler.

[chris-p]

You may find, that under the grease and grime around the shifter handle, the casting is cracked, causing the slop. I am not sure what bolt you plan on shimming, but you cannot shim the center bolt, with shoulder, that pivots the bar.

As Don stated, those pieces are quite fragile for what they are. I have broken a few dismantling them, good thing I keep a few spares! The problem will be, after taking out the screws, sliding the 2 pieces off of the splined bar. Try and refrain from spreading the gap with a flat screwdriver too much, that is where I find they will split, making them scrap.

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