Trojan Boat Forum

Is there any rule of thumb for flushing/cleaning out the risers?

Hank, are you planning on removing and cleaning or are you wanting to flush after use?

Are you having a flow issue?

No flow issue. Just noticed last season when we start her up some rusty cloudy water comes out of the exhaust, not much just on initial startup.

That's normal. Rusty water accumulates in the bottom of the mufflers. Get's blown out upon start-up.

It depends on the age of your risers. If a riser rusts through it allows a small amount of sea water to mix with the exhaust and due to valve overlap and the pulse pattern of the exhaust, some of this sea water goes in the exhaust valve ports where it rusts rings and cylinder walls, and can cause the valve head to break off inside the cylinder. A little rusty water at start up is nothing to worry about. The trick is to replace risers before they start leaking internally.

Thanks very much, I'll be sure to keep an eye on it.

As far as replacing the manifolds and risers, is there a way to check to see if they need replacing or is it just based on time elapsed? My boat gets flushed with fresh water every outing and is stored on a trailer.

Most gas engine risers and manifolds have a drain plug for the exhaust flow area. Before I switched to Cummins diesels (manifolds are anti-freeze cooled and riser is stainless steel), I would remove these four plugs several times a year and look for any water drainage which would indicate a rust through somewhere. This is a 'last chance' warning and if you have water run out the drain plugs, you may already have engine damage. I know of no other way to be sure of risers / manifolds other than changing them every 3-5 years as the mfr's recommend.