The block drain (red hose), is not large enough for good flow nor is it the hottest water source. The hottest source is on the intake manifold just where the water passage comes out of the head, and there should be a bung, as its where the car heaters are plumbed.
The return (blue hose), should go into the circulating pump (not the raw water pump), for the best pumping and again there should be a blanking plug as the car heaters are returned here.
These are always the locations that we plumb the LPG vapourisers over here which gives a good supply of hot water. If your boat does a lot of running below 1500 rpm you can also fit a smaller pulley and shorter belt to the circulating pump to speed up circulation.
The bungs can sometimes be difficult to remove especially on old engines or those run in salt water, but usually a little heat will get them out, then a couple of 5/8" hose barbs with bsp threads can be screwed in and Robert is your mothers brother !!
It's Nice To Be Important But More Important To Be Nice. Keep On 'Footin'
Last edited by Dave2302; 08-17-2009 at 06:48 AM.