Exhaust question

Tarantelle · Feb 7, 2021

I’ve got a 1983 Ocean Alexander 40 with twin Lehman 120’s. I’ve only had the boat about 7 months. The engines have about 5000 hours. At idle rpm’s, the exhaust on each engine spits out at about the same rate. However, once the rpm’s go to around 1100 or so, the starboard engine exhaust doesn’t spit out like the port does. Water flows out of the exhaust well, but not with the strong spits. I’ve 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!

rslifkin · Feb 7, 2021

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.

Tarantelle · Feb 7, 2021

Thanks. Perhaps I was just worrying about nothing.

SteveK · Feb 7, 2021

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.

Arc · Feb 7, 2021

The slightest list will change the exhaust flow. Even 1 Deg.

Flatswing · Feb 8, 2021

Tarantelle said:
I’ve got a 1983 Ocean Alexander 40 with twin Lehman 120’s. I’ve only had the boat about 7 months. The engines have about 5000 hours. At idle rpm’s, the exhaust on each engine spits out at about the same rate. However, once the rpm’s go to around 1100 or so, the starboard engine exhaust doesn’t spit out like the port does. Water flows out of the exhaust well, but not with the strong spits. I’ve 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

Ski in NC · Feb 8, 2021

If exhaust hose has a dip in it as it goes from ER to transom, it will tend to spit more.

BeeJay · Feb 9, 2021

Do you have lift mufflers and if so is the geometry the same, same levels and heights etc. ??

Exhaust question

Tarantelle

Member

rslifkin

Guru

Tarantelle

Member

SteveK

Guru

Arc

Guru

Flatswing

Guru

Ski in NC

Technical Guru

BeeJay

Senior Member

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