My twin 500HPís came with CPC flush kits. I thought they were a good idea and never gave them much thought, until a mechanic told me he didnít think they allowed enough water to reach the pump. He recommended the Merc low water pick up boot. I never liked the boot because it seemed like most of the water ended up on the ground. But what do I know, why not use both! So I went down to OP, bent over, grabbed my ankles and bought the official orange Mercruiser boot. (Iím not blaming OP. They probably paid $40 or $50 and who knows how long it sat on the shelf before I came along to buy it.) Then the hose fitting from the flush kit broke and I really took a look at it. At BEST the ĺĒ hose is reduced to about a 3/8Ē diameter opening, which is further reduced by the plunger that automatically shuts off the water when you disconnect! I am surprised the motor didnít overheat while using this thing! My thought is to replace the CPC kit with a ball valve. Maybe plug up the intake on the outdrive.

Of course using just the boot I burned up an impeller, which took out the plastic housing. I pondered a couple of things on the installation. I have always used Merc special lube with Teflon to pre-lube the impeller. I was reading another thread that advocated KY Kelly or some other water soluble lube. I have never had any problem with grease but was wondering why the preference for water soluble.

I back flushed the oil & fuel coolers, and inspected the thermostat housing. The original gasket between the thermostat housing and the cap was stainless with some gasket material and was solid over that bypass hole in the casting next to the thermostat. The new one was just gasket material and had an opening over that bypass. Any thoughts? I would expect this motor to run a little cooler now. In the past it ran a little hotter than the other one, I am thinking that the gasket on the other one has already been replaced. I also replaced the stainless bolts holding the thermostat housing with grade 8 bolts, split lock washers, and anti-seize. There was some crevice corrosion which made the stainless bolts hard to remove. As I was straining to unscrew them I could see them bending. I was VERY relieved they didnít snap. I rationalized that all the bolts you canít see (circulating pump, probably starter) are steel so these probably should be too.

This is one of those threads that should probably be posted in February but I think every one with flush kits needs to be aware of how little water they allow to pass.