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Re: Time for a new exhaust elbow
Fabricating a 'heat riser' injection loop is commonly done with the QM series Yanmar. Common black iron NPT threaded pipe is the usual choice - hardware store stuff. Your Yanmar distributor will have the exhaust manifold flange to NPT pipe adapter that fits on the 'tail end' of your manifold ... right next to the under-counter supply source of an aluminum Westerbeake 1.5" injection elbow that fits at the top of the heat riser pipe, and with the glass lagging tape that will over-wrap and encase the hot riser pipe.
Typical heat riser: Threaded 1-1/2" NPT Yanmar flange adapter, 1.5" NPT close nipple, 1.5" NPT close elbow, 12-18" 1.5" NPT black iron pipe (straight up), Westerbeake aluminum injection elbow .... use rubber exhaust hose from the previous/OEM installation.
All threaded joints sealed with automotive 'muffler cement', etc. Brace the vertically upstanding riser section with a 1" (flattened and drilled ends) steel or stainless 3/4" steel pipe which is hose-clamped to near the top of the riser pipe and run diagonally to a 'convenient' large bolt on the engine at about a 45° angle to prevent/attenuate vibration of the vertical riser pipe - forms a 'triangle' between the brace, the engine, and the heat riser. All hot surfaces heavily over-wrapped with woven heat lagging (fiberglass) tape. The water outlet of the exhaust manifold is directly connected to the new aluminum injection elbow via rubber hose; suction breaker between the exhaust manifold and the entrance to the injection elbow. The machinery space that the heat riser is located will become 'quite warm' due the hot/dry exhaust pipe etc., so venting the machinery space is recommended.
Last edited by RichH; 08-18-2015 at 02:02 AM.