i have twin 6.2 mpi mercs. I had not used it for about a year, there was a sensor issue and life got in the way. I just serviced the boat to get going again... oil, drive oil, raw water pumps, etc. one engine runs fine, the other overheats within a few minutes of the dock. I assumed thermostat and changed it.... same behavior. It doesn't overheat without load.

blockage? Something else? I need some ideas to check. Anyone have a "how to" on backflushing the engine?

Take the raw water hose off from transom to raw pump. Seperate between any coolers.flush each out backwards. Then put hose on transom fitting and flush out thru drive. Then pull off thermostat housing. Clean it out and pull hoses at the exhaust manifolds and flush hoses out. Don't flush manifolds themselves with engine not running.

impellers good?

how old are the risers? after you flush all your hoses and t-stat id check your risers. there is only 4 bolts that hold them on. you will need to replace the joint gasket once apart. if you do decide to pull off the risers make sure you drain the water out of the system first before you pull them so water doesnt get in the cylinders. Just a thought...

alpha or bravo units?

If alphas did you put the impellar in correctly. The vains need to be going a certain way

July 2nd.

Stock OEM install 6.2 did not use alpha's

Impeller and housing

- never mentioned what raw water cooling side set up was - and what impeller & housing is it the Gen VII water pump (all brass) or earlier version black plastic housing ?

Impeller changing - Always change with a new black plastic housing - wear plate and seals that's provide in the kit.

Gen VII pumps always check for scaring

Water circ pump going bad next thing to look at

Month old thread a newbie resurrected yesterday.

glad it wasnt me