Water leaking out before the exhaust outlet


L

larry1954

New member
I can see quite a deal of water running down the back of the boat before the exhaust exit. The water evidently has passed through the exhaust because it is warm. The boat is a 1997 Formula 271 Fastech with a silent thunder exhaust. Any suggestions how to fix it?
 
I should add that there is water also coming out the exhaust as well, but that is not the only place it appears to be coming out. Engine is a 454 Magnum MPI.
 
Water is coming out outside the boat. (Would be a real problem if it was coming out inside the boat, that is, inside the engine bay.) There is a fiberglass box like structure at one end of which are the two outlets for the exhaust while the other end juts up against the stern of the boat. It is there, at the point where it juts up to the stern of the boat, that water is coming out as well as through the exhaust outlets. I assume that it should all exit at the exhausts and that perhaps some seal has given way and consequently some water comes out here before the regular exhaust exit. Unless it is normal? Not even sure how that box comes off, if it does.

Yes, I assume that the boat still has the silent thunder box.
 
Probably just need new gaskets on the back side of the box that butts up against the transom. They are circular and fit around the exhaust tips. Contact Formula directly or your local dealer. They"ll assist you.

The box, which is where the exhaust ports are located, is bolted to the stern and under the swim platform. Should be 4 bolts that hold it in place. You"ll have to remove the box to get to the gaskets. You do have the option of not putting the box back on. U would just need to install salsbury exhaust flappers. Your boat will be louder, if that's a concern. Another consideration is water reversion which the box assists with preventing. That's your call, do your research first.

I'm one of the many who opted to lose the box.
 
Thanks for that. I will try to remove the box and see what I think from there. I would probably be somewhat inclined to retain the box because of the extra security against water reversion. But I will think it over.
 
Hope this helps.

Factory exhaust tips and the seals on the back of the ST box. The box is off a twin engine setup thus why the ports are so close but you should get the idea.
 

Attachments

  • image.jpg
    image.jpg
    122.8 KB · Views: 21
  • image.jpg
    image.jpg
    155.9 KB · Views: 11
Thanks for the pictures. I wonder whether I could simply use a liquid sealant rather than getting the proper gasket from Formula. Might be easier and do as good or better a job?
 
There are also drain plugs in the bottom of the silent thunder that wear out and fall off over time.
 
That too!

Pretty sure the 271s are okay getting out of the hole. 292s can be sluggish depending on fuel gear people. However any weight you can lose off the stern will help. That box weights maybe 50 pounds dry. Now fill it with water any your talking close to 100 extra pounds weighing down the stern. One of the bolts holding it place under the swim platform had worked itself free returning home from a trip in some rough stuff. I decided to just drop the box altogether. As many of us do I try to modernize my old girl, the newer fastechs no longer have the box so it doesn't look out of place at all
 
Thanks for the suggestions. My wife and I got the silent thunder box off on Saturday and you can see that the gaskets need replacing. The other things that we noticed needed replacing were the butterfly flaps inside the exhaust outlet.

I take the point about the fact that the later models do not have a S/T box and about the extra weight and modernizing the boat. That could well be right. Maybe we will not put it back after all. Then what do we do with the two (rubber like) pipes that exit the transom? Is it to those that you attach the salisbury exhaust flappers or attach a piece of stainless steel pipe first? There is also the two screw holes in the transom. Do we just silicon them up or put a plug in them or try a fiberglass repair?
 
I am definitely in favour of not replacing the S/T box. So I am looking for some through hull stainless steel exhausts with flappers to replace the existing ones (made of I do not know what, hard plastic or something?). I have had no success so far tracking down something in Australia. Any one like to suggest a supplier in the US for something of good quality to do the job? Thanks.
 
Replace your butterfly's and buy exhaust flappers. They have enough sticking through the transom so that you can add a pair... cheap alternative to exhaust tips.

Cpperformance carry's all you need
 
Larry

For the holes in the transom from the thru-bolts that held the box in place. This is what you do.

1- Put a good amount of 4200 or 5200(more permanent) in the hole

2 - Put a bead of 4200 or 5200 around the hole that the head of the bolt will set in

3 - Reinstall the thru bolt and tighten the nut from the inside.

As you tighten the nut from the inside the head of the bolt will set into the bead of 4200/5200 you applied in step 2. This ensures a good water tight seal. You'll get some push out around the head as you tighten it. You can clean it up a little bit or leave it. I tend to leave any push out to ensure I have that water tight seal.
 
Many thanks for this information. I have had a look at cp performance and they do look like they have just what I was looking for. Do you really need the butterflys inside the exhaust as well as flappers on the outside? I suppose it might be extra protection against water reversion.

I think that I really would replace the tips though - make the boat look nicer. Just wonder whether the longer ones (10" beyond flange) or shorter ones are better. I had thought that the longer might be better since they might give more protection against water reversion, but then maybe, since they stick out further, they might be more likely to 'scoop up' the wake water behind the boat when you slow down, whereas the shorter ones might miss it. Any suggestions?

Thanks also for the detailed information about how to fill the holes. I had wondered whether putting the bolts back in might be the best way.
 
The internal butterfly flap on the inside I believe are welded in place so to remove you have to break the weld on each side, not sure how you would replace them exactly. I would keep both. The internal and external flappers are your only lines of defense against water reversion.

If you decide to do new exhaust tips some are clamp ons others you have to completely remove the old tips ,which I provided a pic of in an older post, in order to install the new ones. This may be a little more labor intensive and may require filling the old holes and doing some glass work. Where as simply installing the salsbury flappers takes 5 minutes to tighten all the clamps. Although not as pretty you end up with the same result in the end.

I thought about installing new tips as well but then asked myself " how many people are going to be looking under my swim platform at my exhaust tips."
 
Yes, I can see the argument for not replacing the tips, but then, if I do not replace the tips I would still have to replace the butterfly valve inside each exhaust since they are shot to pieces. That is part of the motivation for replacing the tips - I do not have to worry about replacing the butterfly valves since the new tips will come with those already installed. But I understand that there will be some work to replace the tips completely - unless I go for the clamp on ones. Will have to have a look.
 
You must log in or register to reply here.
Back
Top