Exhaust system issues on a cruiser

[batexp]

This one is a bit complicated but I'll try to give enough details for y'all to understand my situation....

I am working on a 44' 1939 Elco cruiser. The original engines (2) were straight 8 Chryslers which have been replaced with 350 Mercruisers. The exhaust system is hard copper pipe with a few pieces of marine exhaust hose and an old style in-line "muffler". The exhaust exits just above the water line.

When I purchased this boat it ran fine. It was purchased in Ontario and trucked to Texas for restoration of the hull and interior. After a two year stay on the hard it was discovered that (apparently during transportation) water that was trapped in the exhaust system traveled up and over the risers and sat in the engines during that two year lay up, causing massive rust and complete seizing of the engines (in spite of the fact that they were fogged).

Now what I'm trying to figure out is how to redesign this exhaust system so to avoid the trapped water and/or to prevent the water from traveling back to the engines. As is, I am afraid that something as simple as hanging on the hook in mild wave action would be enough motion to cause the trapped water to rush past the risers and cause hydro lock. The boat is now finished the engines rebuilt and is slated to go into the water this next Monday. I need to do something to prevent any more damage from this poorly designed exhaust system. Any thoughts?

 

[Bondo]

Re: Exhaust system issues on a cruiser

Any thoughts?

Ayuh,... Lots of 'em,... Got any Pictures,..??

My 1st thought is, the diagnosis for the water getting where it got to is Way Off...

How deep in the hull are the motors,..??
Is there ATLEAST 13" of freeboard between the outside water level,+ the turning point of the Risers,..??
How far below the risers are the Mufflers,+ any other exhaust plumbing,..??
Does the exhaust path FALL continuously from the risers,..??
Were the motors winterized with antifreeze, or Dry,..??

 

[haulnazz15]

Re: Exhaust system issues on a cruiser

Also, exhaust flappers would have gone a long way to prevent that from occurring. However, there may be several design issues as Bond-o mentioned.

 

[batexp]

Re: Exhaust system issues on a cruiser

I'll get some photos this afternoon and post tonight. Otherwise to address some of the questions posed by bondo, I do not believe the risers are much higher than the outlet rather they appear to be at level. This is a displacement hull and the engines are sitting just aft of mid ship. There is 18' of travel from the risers to the outlet in the pipes. The muffler is a narrow in-line old cast iron style.

The boat is still on the hard but she sits fairly level at the waterline. I have not yet figured out how to measure the level of the risers, so I cant answer that question yet. Being that after running the boat and when I disconnected the exhaust hoses at the risers and when water poured out like mad when the pipes were dropped just a few inches, it is holding water in the system due to apparently being lower than the outlet.

As far as the winterizing question it's irrelevant under the conditions described above. What caused the initial problems of the seizing was the fact that there was water in the exhaust system when the boat was placed on the truck. With that much water sloshing back and fourth through 1700 miles of travel up and down hills stopping and starting. When we finally opened the oil pan we found 2 gallons of water in each engine.

What I'm worried about now is it seems like simple wave action (when the engines are off) could result in raw water getting over the risers. I'll get those photos and more detail today and get back to you soon.

 

[JustJason]

Re: Exhaust system issues on a cruiser

I have not yet figured out how to measure the level of the risers, so I cant answer that question yet.

Easy enough. Get a full 2x4 stud (or longer if you have a wide beam) and lay it across the gunnel. Using a tape measure and drop the tape down to the water (or if the boat is out is out of the water, measure down to the water line on the hull and hope for the best). Next, with the engine covers off, measure down to the center of the exhaust riser using the same 2x4.
As bondo says, if the riser is not at least 13 inches about the waterline, you'll have problems all day long. Pic's or not, you can probably get rid of those waterboxes too.

 

[cr2k]

Re: Exhaust system issues on a cruiser

How about drains for the manifolds?

 

[batexp]

Re: Exhaust system issues on a cruiser

Well after conferring with the old-timers around the yard I have found two solutions. First and the easiest is Mercruiser offers riser spacers in either 3" or 6" sizes. In my case I can only use the 3" spacers due to limited clearance. This will only get me 9" above the outlet.

The second option came from an old Bertram guy. Seems Bertram and other sport fisher boats utilized a "surge tube" design in their exhaust system. This system incorporates a dead end in the straight run of the engine with a "Y" at the top about 2 feet from the dead end. Apparently with the low free-board of the smaller Bertrams the exhaust system was too flat. Most of the earliest boats experienced bad problems when backing down on a fish or while tossing fore and aft with the engines off.

I think eventually I'll use both solutions but will start with the spacers as it is the fastest way to get some height. Otherwise one engine has a droop in the system that I need to adress.

I'd add images but can not figure out how yet.

 

[180shabah]

Re: Exhaust system issues on a cruiser

This will only get me 9" above the outlet.

You stated that your exhaust exits above the waterline, is this 9" measured to the top or bottom of the outlet? 9" + 3-4" (diameter of the outlet) = 12-13".

Why not add baffles in the tubes and/or flappers on the outlets?

 

[Lyle29464]

Re: Exhaust system issues on a cruiser

I have seen many travel lift operators lift boats stearn first and too high. They did this to mine and filled the engines. I took care of it before I left the boat.