Sea Sled madness. It’s in my brain.

Somewhere along the line, you will probably have the tank vented to atmosphere with a fitting on the outside of the hull.
Most of these vents have a fine screen in the inlet and are turned rearward and down to stop ingress of water.
If the inlet hole faces any way forward or into any direction to water flow up the hull, water can enter. Certainly, the inverted loop that should be above the vent inlet will/should keep water from entering this area.
If not, the installation of a clam shell over the vent fitting may help. But then they are prone to hitting docks etc. They do come in different sizes
Another downside of a clam shell over the inlet is they can, under the right rare circumstances funnel water spray directly into the fitting inlet

 

I suppose I could pump out my tank. With the primer bulb. Probably no more than 15 gallons on board.

 

There appears to be quite a lot of build up between the insulator and the threaded barrel of the plug, which could mean that the plug is not running hot enough to burn off a rich mixture.
Possible reason, too rich of mixture for your running conditions,- loading, rpm etc

 

Yes, way back we had some thoughts about the actual dimensions of your present prop; 15 3/4 x 17 was the final bid. If correct, that pitch is too high under the cirkumstances, I'd like to see one step less pitch (which often comes with an increase in diameter), plus a heavy cup. In any case you should carry a spare screw onboard, so try to find a propshop with a good reputation, and talk to them about Serenity and cupping. Standard engine sales crews don't know much about props, so asking them is waste of time.

I'll make a sketch for you showing what to look for, will send mail.

 

@Barry With the aerated water coming from the tunnel, we haven't been able to run at much more than 1400 rpm. So she's run at that speed for a few months. Just not hot enough.

 

Extra firewood in the basement. Cold winter coming.

 

....which reminds me that you were cold in Serenity. In our boat, used for work and leisure, my wife absolutely demanded an old-time cast iron stove for firewood. I didn't like the idea, but you know how these arguments develop.....there now is a classic stove in the deck house. And I have to admit that am very pleased with it!! I'll take a pic later.

 

Definitely need a woodstove. Doesn't have to be big, but there's wood lying on the ground everywhere here.

 

This is the one, pictured when installed in 1989. A bit rusty then; we found it in a shed, cast in 1904 and still going strong, amazing! In summertime we put on a top lid with positioning corners for a lng stove. Locker below is firewood storage. Carpentry is oak.

 

Fantastic!

 

1956 ad for you John...not trying to steal anyone's fire!

 

With the plugs back in, took Serenity for a test run. I was able to plane at 3500 rpm for long enough to burn some crud out of the engine. Did a push against a cliff, but couldn't keep her stable higher higher than 3000 rpm. Kept swinging from side to side. Another fender might do it.

Weirdly, she was cool at 3500 rpm 156°f/69°c, but a gentle cruise at 1100rpm shot the temp up to 193°f/89°c in about a minute.

 

Every ob boat I've ever been on runs cooler than idle with more throttle...

Just make a bridle and run off a tree. If a line breaks you head to sea.

 

I know it's cooler at WOT, but we had three months where she was fine at 1350. Now she's not.

 

Oh. I see. Sorry. I guess 193 is pretty high. I am wondering how these do in saltwater and I am facing same concerns someday. I wondered if I had to flush after each use..

I sent you a message, but have no direct knowledge as much as questions. But I'd avoid running towards the shore in all cases. These, while robust, are not always friendly to dirt into the pump intakes.