3607 Mufflers

[Winegrapewill]

Hey all, I have aa 1989 3607 with Crusader 350hp/454's. I'm getting old and cranky and when I pull into my marina there is always a loud boat following me. No wait, it is me, the echo from enclosed spaces bothers me. Has anyone installed mufflers on a 3607? On the starboard side there is room to replace a 4" fiberglass tube in the exhaust, but on the port side it is not a straight shot and is all flexible hose. Anyone done this project before? Any suggestions woud be helpful. I'm looking at Centek Vernatone as I think they will fit.

Thanks for the help.

[Viper]

I can't remember access to the exhaust run, but check the run to the transom, usually in the aft cabin. Do you not have in-line mufflers there? If not, that would be the place to install them.

[Winegrapewill]

Yes, thanks Viper. The exhaust run is below the bottom of the cabinets in the aft cabin. On the starboard side there is only a straight length of fiberglass tube. easy to get to and replace. The port side is not as easy. It starts under the aft A/C unit (aft to bow) goes below the makeup table (easy) the forward to the space below the head and shower. This side appears to be all rubber exhaust hose and is not perfectly straight like the stbd side. How much would have to be removed to get to this hose and cut/replace it?

[km1125]

Unless they did something different on the later models, on my 3607 those final exhaust tubes were the same. The starboard runs under the cabinetry from the engine room to the thru-hull at the stern, with two access hatches.. one in the closet and one in the second cabinet. The port side is the same length and follows the same path, going under the tub seat, the head, the makeup table and to the through-hull at the stern. You can remove the tub seat and the hatch below the makeup table for normal access to that space. They were both 4" hoses. If you have a fiberglass tube on the starboard side, then somebody probably replaced that starboard side with the fiberglass tube, but there must be hoses on both ends to attach to the elbow in the engine room and the through-hull at the stern.

A LONG time ago I cut the 4" tubes in the middle compartment on the starboard side and under the make-up table on the port side. I installed a couple of "DAPPER" sound attenuators on each side. They were essentially about 14" long fiberglass tubes with some baffles inside. I don't think they made an appreciable difference in the sound though, but it was hard to tell as I did it over the winter and it was hard to compare the sound from one year to the next.

How are your raw water pumps?? Have they had recent major rebuilds? If you're not pumping as much water, you might have plenty for cooling but not enough to fill the pipes which dampens much of the sound.

I have also seen boats that have added 90 degree elbows at the stern so that when you're not on plane the exhaust exits below the water. Make sure there's a small hole at the top though as a "vacuum break" so when the exhaust cools it doesn't suck water up towards the engine.

[Winegrapewill]

My exhaust exit the transom with a straight pipe with a rubber flapper valve. There is plenty of water in the exhaust. Pumps were refreshed this year. It's not gonna fill the exhaust, the inlet is only 1-1/4". I'll have to look harder at the shower seat for removal and get a feeling for what will fit and how to get it in.

I realize that it won't be whisper quiet with mufflers, but I would like to mellow it a little and take the rasp out of it.

There is hoses attatched in the engine compartment to the "y" that feeds down the side. I think the mufflers would just replace the length to hose behind that with another hose to the outlet attached to the transom.

The "DAPPERS" you mention sound similar to the Vernatone. Project will depend on how much cruise time as opposed to work-on-it time I can get this winter. We are year-round in California so the boat gets used year round.

Thanks for the info.

[km1125]

Well, I had thought about different muffler configurations for a while. At one point I was thinking of having custom ones made that would go behind the engines, right in the center. Then you'd take the 3" line from each manifold right into the muffler, and the 4" would go down to the elbow that heads to the transom. It would replace the elbows and "T"s that are in the 3" lines.