volvo 2030/d1-30 mix elbow height vs muffler

[mfair]

I have been reviewing the repair manuals of the Volvo 2030 and D1-30 engines.

both models (closely related) show the exhaust mixing elbow exiting the engine quite low and close to the top of the transmission.

I have always read that the exhaust elbow should be at least 12 inches higher than the water lift muffler to ensure proper exhaust movement and prevent water in the exhaust from flooding the engine is some circumstances. I am not talking about the anti-siphon valve in this case.

Am I mistaken about this 12" requirement?

are there any volvo owners out there whose muffler is much less that 12" lower than the elbow?

i am contemplating some exhaust work this year.

thanks,
Mike

[DougR]

If you can get a 12" drop from the exhaust outlet center line to the input of your water lift muffler you are usually in good shape. The attached page from the Volvo Penta D1-D2 installation manual shows drops considerably less than that.

Considering today's flat bottomed boats, in some cases its very difficult to find the amount of drop needed, and an exhaust riser becomes necessary.

The other thing to consider here is that the muffler shown is the VP rubber hose type, with the inlet near the top of the canister, and the outlet picking up the water close to the bottom. This makes the effective height from the elbow to the internal static water level greater than it seems at first glance.

DougR

[mfair]

Thanks Doug.

I'm going with a riser. Lots of talk on British forums support your view.

Mike