Exhaust Pipe Replacement
Sparked by a thread regarding the replacement of the exhaust pipe. I was looking into doing the same for our boat. I contacted Catalina direct and got the part number, price etc. from them. To my surprise they told me that their part did not include a flange fitting to mount to the engine manifold and that I would have to purchase the part from "Trans Pacific". At Trans Pacific they had no idea how the Catalina Direct part was to attach to their part, i.e threaded fitting or ??.
This has all been somewhat of a surprise to me, since my recollection of the discussion here on the list was that the new "one-piece" stainless steel pipe was the way to go. It seems as though that this is in fact not a one piece part. Since it isn't, I'm not so anxious to replace the exhaust pipe. I've checked the pipe and it appears to be sound and well fitted. The only problem that I have is that the end fitting at the raw water inlet has developed a pinhole leak. I repaired it with epoxy in an overnight stop late last season, but don't want to rely on it for a full season. The part is about 6" long, has a threaded end that screws into the black iron pipe, has a 3/4" "Y" that the raw water hose clamps onto and a smooth end that the 1 5/8" hose clamps onto to take the wet exhaust to the muffler. Does anyone know where I can obtain this end fitting? Frank, Kik N Bak
Considerations
The part you're describing is similar to one I had made when the original exhaust on my boat failed due to corrosion at the weld between the 5/8 inch water injection pipe and the 1 1/4 inch nominal size pipe (actually 1 5/8 inch OD).
Rather than buy from Catalina, which can be a Border Customs nightmare for those of us in Canada, I had a local fabricator, who could weld stainless steel, make up the whole thing out of screw coupled, stainless steel, schedule 40 pipe. The only welding required was to connect the water injection pipe to the last pipe section.
Next time, if there is another, I'll use schedule 80 pipe for the last section where the water injection pipe is welded in. Schedule 80 pipe has a thicker wall but the same outside diameter. I'm fairly sure that the original Catalina exhaust was schedule 80 for the end section. There are two reasons for using the schedule 80 pipe: the hot gas and water form a fairly corrosive mix that attacks the weld heat altered steel and the screw threads remove quite a bit of the pipe wall reducing its strength perhaps too much.
By the way, I reused the coupling to the engine. It can be removed from the exhaust pipe but might require a lot of heat, a very large pipe wrench and a large mechanic's vice. The heat, and I'm taking about to dull red, makes the coupling expand loosening (a relative term) the joint. A couple of strong friends would be a useful addition for this part of the job. Charles Holder, Discover #617 (1988)
My suggestion would be to fabricate from schedule 80 stainless steel screwed pipe and bends. That way you only have to weld the injection pipe into the last short piece of pipe. I found the same piece rotted out frequently, probably due to heat alteration of the metal when welding and the presence of heat and salt water. Using screwed fittings enables one to replace one part and means a lot less expensive SS welding. Lots of pipe-fitters can cut and thread pipe. Two cautions: you'll need to use a thread sealer - I used regular exhaust paste spread on the pipe threads; welding in the injection pipe will distort the pipe section to out of round - have the welding done first, then the pipe cut and threaded. Schedule 80 is thicker than normal steel pipe and provides more metal after cutting the screw threads. As to which stainless steel grade, I'd suggest regular marine grade 18/8. Charles Holder
When I bought my Exhaust Manifold from the factory, they wrapped it with lots and lots of insulation. I'm not sure , but I think the main function is to protect YOU from getting burned. The pipe would run cooler if it had a place to radiate the heat. But I left all the wrapping in place. The results were such that it would not pass the "dollar bill test" that Ron use to talk about. That is, there must be a space between the manifold and the heat exchanger so the they would not rub each other and cause more problems. To solve that problem, the yard man took off the HX and bent the support flange about 1/2-1 inch so that there would be a good clearance. Dave Davis
As far as all the wrappings - they are there to keep all the HEAT inside the riser and not let it get into the interior of the cabin. TRIPLE check that the mounting flange on the engine to insure it is absolutely clean of old gasket material. Then check this again!! If the welding shop was capable of doing a good job of stainless welding, you should be good for another 5-10 years - if the rest of the flange piping is OK. Make sure that you have a slack bend in the raw water line that empties the heat exchanger water into the nipple in the riser. The tip from your mechanic is correct on worrying about a scored or pitted surface on either the engine / riser flanges. What I used for a "liquid gasket" material was muffler patch paste. It's the only material I know of that could stand up to the exhaust heat. Mine is sealed and w/o leaks, 3 yrs later. Ron Hill, APACHE #788
The exhaust flange for the Universal 25 XP is Part # 298599-R14. It cost me $51.90 in Oct.99. From SEA POWER Oakland CA. 510-533-9290 Ask for Colin, the parts man. Make sure they install a rubber hose that has a hump to take up the vertical vibration stress. Dave Davis
Detailed installation instructions
The first step in replacing your exhaust riser is to drain the coolant through the starboard side petcock near the front of the engine. Squirt some liquid wrench on the three nuts that hold the riser and flange to the back of the engine and let it sit over night. I believe these nuts are 7/16" and are best removed with a box end wrench rather than a socket, especially the one underneath. After you remove these nuts, you have to undo the raw water hose from the riser and the two clamps from the inlet exhaust hose to the muffler. With some gyrations the flange/exhaust riser will come out thru the engine compartment.
To reassemble the first step is to put the flange in a vise. Screw the exhaust riser into the flange until you get the angles aligned properly (use the old exhaust riser and flange as your pattern). Then back off the riser counting the number of turns until it is all the way off. With the flange still in the vise, treat the riser threads with some muffler patch and screw back in the flange the same number of turns. Remember don't over tighten because you don't want to have to back off (you may break your seal). You want to end up tightening it to get the proper angle.
Ensure that all of the gasket material is off of the exhaust/reservoir casting on the back of the engine. It's a real bear to get in there and make sure the surface is clean, but quadruple check this or you will not get a good seal and lose your coolant (when you refill) and have to start over with a new gasket. Make a dry run without the gasket just fitting the flange/riser assembly in place. As I mentioned in the Nov 98 Mainsheet Tech Notes, try the "dollar bill test." It's more important for a 25XP with the larger diameter heat exchanger than the M25, because the factory may have wrapped too much insulation in that area where the riser goes over the heat exchanger. I couldn't get the flange to completely seat until I cut out some of that insulation. If you can pass a dollar bill between the riser and the heat exchanger, you are in good shape. If you can't, whittle away some insulation.
Also measure the length of hose that you'll need between the riser and the inlet to the Aqualift muffler (with a new riser it may not be the same distance as it was with your old riser).
After you are sure the flange/riser is going to seat and that surface is absolutely clean, place the gasket on the three studs. I even used some of the muffler patch around both sides of the gasket to make sure I had a good seal. This is a perfect time to install the single hump hose which I wrote up in that same Mainsheet article and again in the Aug 99 issue( the 81/2" hose from the factory is $33.75).
Up to this point, disassembly and reassembly has been a one person job. Now you need a second pair of hands. As one person aligns the flange with the three studs on the back of the engine, the other person aligns and inserts the single hump hose into the flange and muffler inlet. Tighten down the three nuts to secure the flange, double clamp the single hump hose on the flange and muffler ends. When I attached the new raw water hose from the anti-siphon, I made it a little bit longer than the original factory installation so it could flex a little and put less strain on that welded nipple that goes into the riser. Re-clamp that hose and you are ready to refill the reservoir with coolant (50/50 Prestone).
To ensure that you don't have an air bubble in your internal cooling system that goes through the water heater, remove the inlet hose to the thermostat housing. Insert one of those Par Junior Pumps and with the pump exit pointed into the reservoir, keep pumping until you have coolant being pumped back into the reservoir. Remove pump and insert hose into the thermostat reservoir and tighten the hose clamp( you shouldn't have to "bleed" that system as all of the air has been purged) . Recheck that the reservoir is full & replace the cap, start the engine and check for any leaks. You should be in good shape. Hope this helps. Ron Hill, APACHE, #788
A Mainsheet letter written about draining the expansion tank is good advice and a good way to drain the tank. I have replaced my exhaust system twice and I only have this to offer. Using the drain plug does drain the tank however when you remove the gasket for the flange the remaining fluid will drain out the rear of the tank. If you use the drain plug the fluid (may) end up soaking into the engine compartment sound proofing. If you drain it from the rear it will fall onto the fiberglass and end up in the bilge. I also suggest taking this opportunity to wash the tank out to remove whatever particles have settled in the bottom of the tank over the last 11 years. Just a thought because you will have to replace the gasket no matter which way you go. You will also notice the gasket has a stamp on it indicating which side goes against the tank, (very important). Rich Dwyer, Rebellious #328
I did the draining today and caught maybe 95% of the coolant. I used a small plastic bendable cup and used my finger to stop the flow every time the cup filled up. I also spayed the the bolts with liquid wrench. Dave Davis
