Morning, all. This question may have been asked here before now, but if so I didn't find it in the threads, so here it is:
The
engine on the sailboat Sequoyah is a 1999
Yanmar 3GM30F. It has a cast U mixing
elbow, high rise, 2" outlet, 5/8"
raw water inlet, mounted on a cast riser (manifold) protruding off the upper stern end of the
motor. The riser is attached to the
engine with four machine screws, or bolts. I understand this is a standard configuration for this engine at the time it was made. I don't know, yet, what material the
elbow or the riser are made of. Iron,
bronze, stainless? The elbow has the original
Yanmar silver gray
paint on it, never cracked at the joints. The engine itself has only 300 hours of operation, so that isn't surprising.
I'll find out just what it is and whether or not it's stopped up next week when I remove it, but I think there's a good chance the elbow is clogged with soot or
corrosion. I am not getting proper
cooling for the
motor, and after a quarter hour of operation warmth starts backing up into the
raw water hose leading from the
pump to the exchanger, as I think it shouldn't. If so, I may be able to clean this elbow, but given its age that may not be the anticipation I ought to have here.
I hear Yanmar no longer use this design. I can get a direct replacement, affordably for cast iron, unaffordably for cast
stainless steel. I also can get a reasonably priced mixer of a different, nonrising design from
Exhaust Elbows, fabricated of
stainless steel tubing. Replacing this OEM mixer with that one would eliminate the high rise. I even have heard of people who have built their own no rise mixers from iron pipe, which strikes me as a
cheap solution that would probably require more frequent replacement but that might
work.
My question is this: Is it important to keep that rise? Is the purpose of it to prevent
water from flowing back to the engine when the
boat is under sail and heeling sharply? Have Yanmar indeed abandoned the high rise design on newer engines, and if so why? Did it not
work out in practice, or am I mistaken in my thougth they no longer prefer it? In short, would there be a
danger were I to switch out the old elbow and riser for one of the
Exhaust Elbow products?