Good catch and point! Either way I wanted to rebuild the carb. I didn't trust it. I'm going to rebuild the carb, refill the a/f and double check the timing to see that it's where it should be and not advanced. I'm also going to still install the clear tube for good measure.

On marginal cooling systems, less timing than ideal at idle creates higher coolant temps.

I’m old enough to deal with this on many of hundreds if carbureted cars back in the 80’s and earlier. Overheated cars where littered everywhere on sudes if highways. Especially traffic from toll booths and off/on ramps.

I'm old enough to remember those days as well. I put a Pontiac 400 in my first car over the winter before I got my license. If this was a car, I'd be done by now.
I know I set the timing on the boat, but with so many things going on and with it being a new build etc., I'm not taking anything for granted. It was real tough seeing the timing marks and I could easily have made a mistake. Being way off could also explain lack of power to get up on plane. I still haven't pulled a plug. This reminds me I need to do that. I'll try and do it tonight.

Rebuilt the carb and refilled the a/f. The guy at Monitor said he thought I had air in the closed system. It's running excellent except for the heat. I let it idle with the cap off for 20 min. It burped a little once, but not as much as I'm used to seeing on a car radiator. The temp stayed at 210 the entire time once it warmed up. One end of the heat exchanger stayed a little cool, but the rest of it was 207. Risers still cool as well as the exhaust water out the drive. Monitor said if the water coming out the outdrive is cool that I'm getting plenty of raw water for cooling. The problem IMO is with the heat exchanger. Emailed them yesterday, but nothing yet. I'll try calling again.
Here's a vid from yesterday.
https://youtu.be/KekmU_mr6PA

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https://cimg7.ibsrv.net/gimg/www.off...9a80aa8816.jpg
https://cimg1.ibsrv.net/gimg/www.off...12fb2c9856.jpg

Have you considered acid bathing the heat exchanger ? Not really hard to do except you have to mess with a/f solutions and burping again .
Those little copper tubes can get grungy (on both sides) after time and loose their ability to transfer heat quickly while the raw water being dumped out would still be cool.

Unfortunately it's brand new. This is a new install that I haven't been able to dial in.

All fixed. Yesterday I pulled the risers and elbows off. Monitor wanted me to replace my lower bronze exhaust 90* elbows with their copper ones because they flow better. Before I did that I figured out what was the real problem. Monitor suggests putting the top coolant fitting in the riser, but doesn't say you have to. Mine was still in the top of the manifold. I think it cause an air pocket or something. Either way, I'm running at 160*-165* and all is right with the world finally.
Thanks for all the suggestions.
Happy Independence Day!

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