I made a plate to go on my Imco Powerflows. The water passes through these on the way out the exhaust. Haven't had a chance to try them yet. My reason was to use an A/F ratio meter.

I have run EGT's in snowmobiles for years. They are only useful as a tool for determining problems or correcting setup if you take your boat to somewhere with substantial changes in altitude or temp. Two strokes are supposed to run at 1250, but I have had them burn pistons at 1050 and had others that ran great at 1300. You should tune your engine by reading the plugs ect. and then see where your egt's are. they will then be a good indicator of potential problems or tune up change due to altitude or air temp change. Just my 2c's worth.

Just remeber O2 sensors are very tempermental to water!!!

My aluminum plates look very much like Mopower's except they are a wedge to align the tailpipes with the exhaust tips. I had a bung welded into the starboard aluminum wedge. I was very concerned about egts since I am running a 540 9.0:1 engine with a M-4 Procharger. I also have a modified Nickerson carb in the box set up and wanted to be able to watch changes in egts from the dash. I realize that the best location would be between the cylinder head and the exhaust manifold, but I had to have wedges made anyway and I was more concerned with sudden change in egt vs. using it to get the jetting dialed in. That was done by plug readings. So far so good after a season and a half. I have to agree that the gaffrigs probably read 200 to 250 degrees hot. At WOT I see 1450 between at the wedge, and I have to believe that it is hotter at the exhaust port on the head.

Ty

Wedge plates...good idea. Luckily , my exhaust is forgiving enough I didn't need them. Flat was OK

J-Bonz ,
That's why the O2 sensor is between the manifold and elbow. I sure hope to he11 there's no water there or I have a more immediate problem