Quote Originally Posted by whitehead249 View Post
A couple more questions should I run it with the tstats and poppet valve? I also put a different lower unit off a Mariner 150 i was wondering if that could be some of the problem? Any and all help would be appreciated.
The 150 gearcase probably has 2:1 gears in it (a 225 Promax has 1:87 to 1) not a huge issue and makes no difference in respect to cooling. The Promax is designed to run with stats, a poppet and a 2 piece exhaust plate, it's a "consumer" high performance motor not a race motor. Race motors have 1 piece exhaust plates no stats or poppet, turn a bazillion RPM and blow up a lot. 2 million idiots in this world yank the stats and poppet in a fishin motor "cause that makes it a race motor" but it doesn't, however it does make them blow up.

All that said, you're in a tough position. You have a great short block but it's an EFI motor converted to carbs. A motor like this needs somebody with lots of experience to get it sorted.

I would start with a good water pressure and temp gauge (verified with a heat gun on the heads). Replace the water pump assembly (never overlook the simple stuff). Post your temps and pressures at idle, 3000 RPM and 5500 or so if it's not running too hot.

Next I would shop for a 225 Promax exhaust plate that's not been molested. The exhaust plate sits under the powerhead and shouldn't be confused with the exhaust divider that sits under the coils.

Once you've done that you'll have a chance to straighten this thing out. The reason somebody ran this with no stats or poppet is because they were created a massive compensation for some other design error in the Frankenmerc process.