Wouldn't the motor be running hot if there was a problem with the impellor or a block in the cooling system?

Pictures would help.

Are your thru hull tips lined up straight with your exhaust riser outlets? Is the 4" rubber hose that goes between the risers and the tips as straight as can be so that there is no direct contact with the rubber exhaust hose and the inner riser pipe? What I'm getting at is if there is direct contact between the hose and the inner pipe you'll get a hot spot and cook the hose out in that spot. Even if its close you could pinch off the water supply and still cook a hose and blow a hole in it. If you patched it with a beer can it doesn't sound like you cooked the entire hose, just burned a hole in them right?

I think you might have something there. The alignment is a bit off and the end of the stainless tailpipe is touching the inside of the rubber exhaust tubing. Most of the inside of the pipes are cooked but the actual hole is burnt about two inches back from the contact point...same situation on port and starboard.

Don't know if this would make a big difference but looking in a parts manual that engine calls for a 140 degree thermostat.I run a 505 stroker and have my block half filled with block hard.Using the 140 thermostat it only runs 145 and at the most 150 if I run long periods over 5300 RPM. I have my sea water pump connected to a thru hull water pick up beings I have a TRS drive which doesn't have a water pick.I'm assuming your using a Bravo drive and picking up water through it.May flow a lot more if you convert to a thru hull pick up.You only use about 1 1/2 ft. of 1 1/4in. hose between the pump and pick up. Very easy to install. Don't mean to sound stupid but what are you meaning by 170 at FWC? By the way my exhaust only get warm,never hot.However mine don't use a rubber hose section.Their Hardin Marine one piece stainless all the way out through the transom.

I went through the same thing with those EMI thunders two months ago (search my post)

These are wierd risers. I had two much angle, the 4 inch bellows and risers where at different angles. It did not take much. See my pictures, I ended drilling a small water hole in the bottom of the riser and fixing the angle and the problem went away. They need to run parallel to each other to mix the water correctly.

IF you are running good water temps, which you say you are, I dought you have impeller problems.

Here is the link with pictures.

http://www.offshoreonly.com/forums/g...look-like.html

Thanks for the info guys! My risers are similar style to the ones that you drilled except they're stainless with a little different geometry. I think I'll try most of the ideas here....I'll see if it's possible to drill a small hole in the bottom of the tailpipe. Moving my raw water pick up to a thru hull sounds like a good idea, but probably a last resort for me....my hands start to shake a litle when I bring a hole saw near the hull.

Looking at the Eddie Marine website it says that the style of tailpipes I have are for Silent Choice which I haven't got....I wonder if that might be giving me grief?