Help with Merc 5.0 cooling issue
 

Hey everyone- I have a 2005 Mariah with a Mercruiser 5.0 engine that was in outside storage for 18 months.

I pressurized the oil system, put new gas in, checked all the fluids, and cranked it up. It started right up, on the first spin.

Everything seems to be fine, except that the thru hull exhaust is only spitting water out the starboard side when fed water thru the earcups and motor is idling. There actually seems to be an abundance of water coming out the starboard side, like there is a blockage or something. The starboard side riser is cool to the touch, the port side is HOT, and no water is coming out the exhaust port.

Engine is idling perfect, oil pressure is good, no steam or anything to indicate a cracked head or similar.

Engine temps are fine...so I'm wondering if I need to take the port riser apart, or start at the therostat?

Since water is getting to the motor and riser, that should rule out an impeller problem, correct?

check the hose going to the riser at both ends, if getting water flow thru hose the riser is plugged

Thanks so much for the reply.

I did as you said, and hooked water to the riser hose, and water poured out the thru hull exhaust port. I would assume that means theres no restriction there?

I then proceeded to take the water neck apart, and found that the thermostat was completely frozen/rusted shut.

I got the new stat in tonight, and have everything back together, but ran out of daylight so will have to wait till tomorrow to test it out.