Risers getting to hot.
 

Hey guys... it’s been awhile. I’m having an issue that I just can’t seem to figure out so I’m throwing it out to the experts. 6.2’s with Stainless Marine manifolds other than that totally stock. Port motor steams, and the risers are hot as hell, but the block seems cool. After running I can take the block plugs out of the bottom of the motor and the water is only warm, but I still can’t put my hand on the riser. I have taken the thermostat out. No water in the oil and everything else seems fine. Any ideas on where I should be looking to solve this????

Risers. Usually steam and a hot riser is an indication of a bad riser gasket or partially blocked riser (i.e. rust). You stated you have Stainless manifolds, but what are the risers made of? I would start there.

Water is not circulating through your risers at a fast enough pace to cool them properly. They get hot and steam is produced....

Risers are stainless and not blocked. I have backflushed the mainifolds but not yet removed them. Other motor is running cool and has the same amount of flow.

I just took the manifold off to try and shake any obstructions out... got a closed handfull of sand- not much. But I did have white crust from the top of the riser all the way down and into the middle two exhuast ports on the head. Not much but it was there. Pulled all the plugs and they are all a light white/brown and all four seem about the same. I'm still stumped. I will try and switch the raw water pumps tomorrow and see what happens.

How are the risers getting hot, yet the motor is only warm?

Are you dumping water to lower pressure?

When they were installed did you or whoever did it change the plumbing? If it still is stock the 6.2s use a check valve on the bottom of the manifold, its possible that it is clogged or stuck. Did it always do this or did it just start? If I remember correctly your boat was repowered by Pantera a few years ago.

May be losing some pressure. Sand in your manifolds got there somehow. That somehow would take it through the water pump. Sand in the water pump could be a killer. Maybe your losing pressure at higher RPM levels due to premature wearing in the water pump? Forgot about the check valve also...

There is really only a few things it could be. White crust is dried salt/corrosion. It got there somehow...

Bravo Fever....

Does anyone know the part number for the plastic hose retainer??

Also do you think it's plausible that with reduced water flow it made it easier for saltwater to back up into the two middle cylinders??? Or should I be hunting another problem??

That makes sense. It has enough flow to cool the engines, but is not bypassing as much water to the exhaust.
Not sure of the part number, but I'm sure you can find it on www.mercruiserparts.com
I would order 2 of them, since the other one may not be far behind.

try switching the two thermostat housings. if prob goes to other engine you have it.