Replaced head gasket because of loose bolts, (see and So It Continues part one) fire on rack connected to hose, runs fine good water out exhaust, unable to bring up on hose hookup, starts collapsing the supply hose.Today I take her out, fires fine, leave marina, on plane, port motor temp rising. stop. still have good water from exhaust. but block seems alot hotter than exhaust??? I have the thermostat out, I pulled and checked the sea water pump, Gen VI Big block,Stainless marine exhaust, original Thermostat housing 1983 454 version,Still have water circulating pump on engine, water temp gauge read 185, Starboard side(left) of the engine hotter than the port ?? What is causing poor water circulation thru the engine block? this experience was the same with or with out the thermostat installed Other engine runs 150 temp all day??

Check to be sure the stainless fitting in the front of the starboard manifold is not bottomed out against the inner manifold. Had a set of SM manifolds that came with fittings that were too long. When bottomed out it restricted flow.

Totally agree! I shaved about 1/4" off the base of my fittings from manifold to riser because they were way too long!

Also, you may have some crap or corruption in your cooling ports either in the head or the block.

At another outside guess, I suppose it is possible that one side of your circ pump is worn unevenly and that has caused a pressure drop to that side's inlet?

If it were me, I'd pop the circ pump off, make up a block off plate with a hose fitting (barbed & screw in) in it, block off the other side of the motor cooling intake, hook a hose to the fitting and try flushing the block through. Then swap plates and sides and repeat.

First I'd check those manifold fittings though, but you said you're getting water out both exhausts evenly?

Isn't boating fun??

Same manifolds that I had on these motors for 10 years, no problems with cooling last year, just oil pressure.. another story, I am going to try to flush the block, check circ pump, t stat housing..thanks,

As these out guys have said check the fitting, if all is correct. Check the molded rubber hose between the helmet and the gimbal assy fo leaks or being twisted, if thats ok remove the plastic 11/4 fitting on the inside of the transom and check to see if the plastic insert is not restricting the water flow this is a common problem, corrosion will crush this to the point of reducing the water flow.

Pulled the plugs on the left bank.. water in # 6 and # 8....cracked head or block..who's guessing??

Riser gaskets failed...or blown head gasket..

I had a block that was filled up with sand...Temp guage mounted on intake started to creep up but block was already cooked & head cracked. Maybe you have crap in your block ?
Just a thought & good luck !!

Weird..pulled the head and was cleaning it when I found the main water passage in tie head @ # 2 cylinder was plugged with black sand..I looked thru the intake and block, this is the olny sign of sand WTF ??????????

ttt