Nope.. no other symptoms. I hear it is common to have engine temps fluctuate a bit with a crossover. I know the head gaskets are correct. Merlin III block and canfield heads. spoke to both companies before I put the long block together.. Exhaust was just tested when I had the O2 Sensor bung & Pyrometer bung installed. CMI did it. I also run a mercury pressure dump valve right after the sea water pump and a pressure gauge.. pressure never goes over 30 psi.. and plugs look great at every change. leak down test was awesome as well as compression.. motor runs fine.. real fine.. going on year 6 now.. just a small (and livable) temp issue.. I will try the lines and see what happens.

All summer I was fighting a problem with #8 cylinder sticking exhaust valves. I took out I think 3valves this summer, hit the piston on all occasions and bent the valves pretty bad. Luckily they did not take out the piston, Good Ferrea inconel valves.

I did some testing on the hose with an infrared pyrometer. Cylinder heads around #1 #2 and #7 were running around 190*F and cylinder #8 was around 300*F.

I took the heads off to look for obstructions in the block and I found none, I drilled more water ports on the head surface of the head and still no help. I then drilled out the back of my manifold and added dumps. This seems to have fixed it. I have 4 Merlin heads and same head gaskets on my twin engines. These heads were on other engines with no problems and I had GM 088's prior with no problems. I can't explain why I had this problem but the drilled out rear intake manifold solved it.

Wow.. big difference indeed... Sounds like a world of trouble. gives me an idea though.. I should grab one of those guns from the local shop and see what temps I am running..

Panther
Any ideas where I can find stainless?

McMaster Carr should have what ya need!
http://www.mcmaster.com/#stainless-s...ttings/=5l2u9y
http://www.mcmaster.com/#stainless-s...ttings/=5l2uw1

So.. after much thinking and discussing I have decided to break out the drill and go through the transom..

Can I just run a 90degree fitting on one side to a "T" and a 90 degree fitting from the other side to the "T" then from the "T" out the back? I am assuming we never touch the front 2 holes in the intake.. Just the rear 2?

What fitting did you use from Eddie???

One of the most popular and trusted marine performance motor uses a recirculating pump-----Merc HP525. I will be using a recir pump and thermostat setup. I just like the fact that the motor is in control of the water and the consistency of temps within the motor itself.

Yup.. I have heard it from my builder many times.. Big Merc fan.. works on them all.. from 496 up to the new 1075..

but my setup is done and I don't want to add belts, therm. housing redo all the plumbing ect.. many people here make a crossover work and they work well when setup properly..

Spoke to Hardin marine today in great length.. They think (and perhaps rightfully so) that my crossover is at fault. the bypass is a small 8an line.. only 7/16 thick. so.. when the thermostat opens a ton of water rushes through the block.. cooling down quickly.. then, the thermostat closes.. temps rise.. and the process starts again.. they said I need a cross over with a bigger bypass and that will help a ton.. also going to try their thermostat spacer.. run the rear lines from the manifold to the spacer..

and if that don't work circ pump here we come..

After you mentioned that. There is the old trick where you take off the bypass, and drill a couple small holes in the thermostat base. This lets a little water bypass through to keep the exhaust from overheating and still allows the thermostat to work properly.

This keeps the drastic ups and downs from occuring, and the engine stays at a more consistant temp.

I have drilled my thermostat.. depending on how many I drill, I can regulate the temp "OK".. like a 140 thermostat with 3 holes I can get to around 130 constant.. BUT.. each side of the intake is at different temps. as much as 15-20 degrees... i know the larger bypass will help a bunch.. also.. moving water from the back of the intake up front will make a difference as well.. might run a 4an line from/to each front intake port as well..