Exhaust Shutters ???

[tonka_shores]

Where are my exhaust shutters located? If damaged or defective, can they cause an overheating condition? How do I check them? The boat is a 1972 MerCruiser 888/Ford 302.<br /><br />I've eliminated overheating suspects such as lower unit impeller, (I've got gushing water from it that increases with RPMs) clogged mainfolds/risers, (had them off, flushed them, water runs freely through) engine circulating pump, (had it off, good condition) new thermostat (installed correctly). The only other thing I can think of is a blockage below the dumps. This thing is killing me.

 

[Boatwizard]

Re: Exhaust Shutters ???

I feel ya, had several that did that years ago. There are several ways to go.<br />1 (fastest fix) buy a thermostat neck like inboards use, with 4 hoses. Incoming water, water pump and two hoses to the mainifolds. Run the two hoses to the front of the maifolds then run the manifold hose at the rear to the elbow on the oposite side. The water then travels down the manifolds and overboard instead of circulating with the engine cooling water.<br />2 try drilling a larger hole in the gasket at the elbows, that helps but usually doesn't make running hot at WOT go away.<br />3 The old manifold housing can be drilled in a way and the hoses rerouted to make the water pass through the engine only once and then overboard. This is what you do to a boat that runs in 90 plus degree water and is on its last leg. The motor will run stone cold. <br />Go with number one and you should get it under control. Make sure you use a 143 degree thermostat.

 

[northvanwatertaxi]

Re: Exhaust Shutters ???

Hi tonka<br />have you done this using a hose when the boat is out of the water?<br />New water pump if yours is over 1 season old<br />flaps are located on the bottom of the Y tube.<br />there are lots of easy ways to check that everything is flowing well just use a garden hose, unplug the raw waater hoses and flush the manifolds an risers to find out if they are ok<br />I just took my 888 302 merc leg engine out (alone) and changed the bell housing tomorrow I will be finished