Exhaust replacement
 

I obviously need to re-do the exhaust on my 1974 Grampian. Question is: should I duplicate the riser (I can add 3 inches to height) and eliminate water muffler or use the brown thing?
Attachment 13723

OK, I'll jump in here.
First, I've never used a mixing elbow like the brown thing. There's a history of them here on the forum getting clogged. Is yours new or is it a used (questionable) unit from eBay?
I have used a riser, and they are fine. Taller is better. The only down side to them is they take a lot of space and require a lot of insulation to protect your boat.
I'd be tempted to try the mixing elbow if it's a new unit. Otherwise I'd build a riser of known performance. Might even think about stainless..

I wouldn't leave the water lift out of the system.

+1 on leaving out the brown mixing elbow and building a stainless riser.

+1 on NOT leaving out the waterlift muffler!

Thank you
 

The brown thing is from a used engine I aquired that would not run for longer than 30 min. Perhaps the brown thing was it's problem.
I am trying to reduce back pressure in the exhaust system. Moyer has exhaust setup from catalina diagram that they suggest could be used without a water lift muffler?

My problem
 

I am trying to find out why my plugs foul in less than 8 hrs of running. Identical Black sooty fouling on all 4 cyl .
Vacuum at idle is 18-20, and goes to zero at 3/4 throttle. Cyl compression is 90, 95 , 95, 90. Exhaust is blue-gray on start, clean at 165 degrees, timing is at tdoc. I run the slightly hotter plugs and engine starts incredibly well.

Whether or not a particular exhaust style will work for your boat is dependent on relative elevations of the engine exhaust outlet, available space for a generaous hot section rise and downhill run from the top of the rise to the exhaust thru-hull presumably at the transom at even keel AND heeled under sail. Just because Moyer offers a straight pipe system does not mean it will work for your application.

Studying the Grampian 30 drawings online it appears to me there is enough rise available for a standpipe system on the port side under the cockpit seat. If it were mine that's exactly what I would do. Did we determine your Grampian was a 30?

Grampian 30
 

Yes, a wonderful grampian 30std

Back again. I've never had a boat with a water lift. Perhaps joe or ed could explain why they're so good. I can only see them adding back pressure.

Al, they are a compromise. Pumping water uphill is always an issue.

I agree with Neil that if you want to incur the expense and have the space in the boat, a stand pipe arrangement would be better.

I think we agree.
If your engine is in the basement and your exhaust has to go out through the front door, you have two choices.
One is the water lift. Use the exhaust to pump the water.
Second is the riser/mixing can. Long hot pipe, water injection, then out.
Not going to debate the pros/cons of each.

It isn't pro-con, it is what is physically possible to do.
On my boat using a riser to keep water out of the engine is essentially impossible unless I run a dry exhaust 10 feet long up and around a couple of things into the main cabin and back down.
Like almost every sailboat I have ever seen, I have a riser that fits on the engine feeding a waterlift and then overboard. Some boats have the good fortune to have the space for a standpipe, which is a better system if you can fit it.
Riser at the engine and then overboard is very common on powerboats. There may be a sailboat or two like that, but I have never seen one.

The black sooty fouling on all 4, the blue-gray smoke, and the easy starting are all indicative of a too-rich mixture. When the mix is properly tuned, an updraft carb like ours should require full choke and be a little hard to start. I have confirmed this with a fuel:air ratio gauge. Mine is mixed to to the proper 14.7:1 and it always takes full choke and three tries to start when cold.

As for the waterlift, its just a noise issue. The A4 can be surprisingly loud without a muffler. But it will run fine. You'll just quickly tire of it!
With my waterlift, the engine is so quiet that the blower makes more noise than the engine at idle!

Whoa, Ed. A waterlift does a lot more than muffle. In fact, in most cases it's critical for the boat's design and engine placement. Muffling is an unintended side benefit.