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Old 02-07-2021, 07:39 PM   #1
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Exhaust question

Iíve got a 1983 Ocean Alexander 40 with twin Lehman 120ís. Iíve only had the boat about 7 months. The engines have about 5000 hours. At idle rpmís, the exhaust on each engine spits out at about the same rate. However, once the rpmís go to around 1100 or so, the starboard engine exhaust doesnít spit out like the port does. Water flows out of the exhaust well, but not with the strong spits. Iíve recently installed the new style raw water pumps on boat engines, but had the problem prior to the pump change. Any ideas why the exhaust would stop spitting on the starboard engine?

Thanks for any ideas!
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Old 02-07-2021, 07:41 PM   #2
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If there's adequate flow, no excessive steam under heavy load and temperatures are good, it's probably fine. The geometry of the systems might be slightly different, leading to one having smoother discharge flow than the other.
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Old 02-07-2021, 07:45 PM   #3
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Thanks. Perhaps I was just worrying about nothing.
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Old 02-07-2021, 08:12 PM   #4
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I agree with post 2 and will add.
Look for a restriction in the flow. check the temp of the exhaust riser on both and if there is a noticeable difference look further.
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You only need one working engine. That is why I have two.
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Old 02-07-2021, 08:25 PM   #5
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The slightest list will change the exhaust flow. Even 1 Deg.
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Old 02-08-2021, 09:19 PM   #6
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Quote:
Originally Posted by Tarantelle View Post
Iíve got a 1983 Ocean Alexander 40 with twin Lehman 120ís. Iíve only had the boat about 7 months. The engines have about 5000 hours. At idle rpmís, the exhaust on each engine spits out at about the same rate. However, once the rpmís go to around 1100 or so, the starboard engine exhaust doesnít spit out like the port does. Water flows out of the exhaust well, but not with the strong spits. Iíve recently installed the new style raw water pumps on boat engines, but had the problem prior to the pump change. Any ideas why the exhaust would stop spitting on the starboard engine?

Thanks for any ideas!
You know about American Diesel - the Lehman gurus right?
First things to rule out is: pulling the heat exchanger cap to ensure no old impeller blades or (most common) old pencil zincs broken off & captured in the input side of the heat exhanger raw water loop. If no improvement, consider cleaning the raw water circuit/heat exchangers with Barnacle Buster or RidLyme
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Old 02-08-2021, 10:07 PM   #7
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If exhaust hose has a dip in it as it goes from ER to transom, it will tend to spit more.
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Old 02-09-2021, 02:05 AM   #8
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Do you have lift mufflers and if so is the geometry the same, same levels and heights etc. ??
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