Dual heat exchanger on Mercruiser 470

[achris]

Re: Dual heat exchanger on Mercruiser 470

achris Will it be the same with a 4.3 with a hullthru system? You wont get that pressure in the exhaust system. So will it suck water back in the cylinders on idle ?

You wouldn't get the exhaust gases in the cooling system with through hull because, as you surmised, there would be no water in the water passages in the leg. But also Merc changed the design when they went to Gen II legs. The water pocket cover is now part of the same casting, no gasket to leak. I guess that was one problem they were willing to address, overheating because of leaking WPC gaskets....

The answer to the second part of your question is, yes, water would be sucked back into the cylinder (at idle on flushers) if there is no back pressure on the exhaust because even with through-hull the water still exists the engine through the exhaust elbows (which is where the water that is sucked back in comes from).

HTH,

Chris........

 

[achris]

Re: Dual heat exchanger on Mercruiser 470

.... a real bummer to extract 3 broke ss screws in cast alum.

You got lucky... Most of the time all four screws break off. We made a jig for drilling the broken screws out. When we got one hole free we screwed the jig down and drill the rest of the screws out through the jig. We even had drills especially modified so they were long enough to use a drill without cocking it sideways... We didn't do the job that often, but when we did it was a real mission, lots of oxy to melt out the cover and then lots of patience to be as gentle as possible removing the screws.

Chris........