Exhaust Soot in U-Joint Bellows - '96 B III

[NoWorries]

I have a '96 Mariah, with a Bravo Three drive. Going over everything, getting ready for spring, I pulled my drive to lube and check gimble bearing and U-joints. I noticed soot buildup inside the u joint bellow cavity, aft of the actual bellows. Attached is a descriptive pic of what I have and how it looks. Is there supposed to be a seal around the exhasut port mating surfaces? I would hate this carbon build up getting into u-joints and a gimble bearing. I haven't ever had any Bravo experience, just alphas. Is this normal or is a seal missing? Could I use an hi-temp sealant and make a seal here?<br /><br />Thanks<br />

 

[Don S]

Re: Exhaust Soot in U-Joint Bellows - '96 B III

I've never seen this happen before, but there must be some serious back pressure to be able to push the exhuast up into the upper area. There isn't supposed to be a gasket on the exhaust section. I would look for something in the drive causing excessive backpressure. Like a broken exhaust shutter or something. Pull the prop and look inside the housing, also look from the side the bellhousing attaces too.<br />Have you had any loss of top end power/speed/rpm?????

 

[NoWorries]

Re: Exhaust Soot in U-Joint Bellows - '96 B III

As far as loss of power, rpm, etc, I don't really know. I bought this boat used this past October, and only had it out 3 times before winterizing. It runs great, starts good, idles good, accelerates good, tops out at 60mph@4750 rpm. I know that is exceeding my WOT RPM a little, but it's slightly underpropped for watersports. The engine is a 7.4 Bravo 454, 300hp.<br /><br />Every time I have pulled the boat out of the water, there is quite a bit of this same exhaust soot built up on the transom and under the swim platform. Could I just be in need of a tuneup and get rid of the soot all together? Maybe a good dose of sea foam or water down the carb to get rid of carbon build up? If everything else has this buildup, I'd hate to think what the inside of the engine looks like.<br /><br />(BTW, speaking of pulling the props, can someone reccommend a prop wrench that fits both nuts on the Bravo III? I have all sorts of tools, but nothing big enough to fit the front prop nut. I'd like to have a simple prop wrench to keep in the boat, but can't find one for a B III.)

 

[TilliamWe]

Re: Exhaust Soot in U-Joint Bellows - '96 B III

do a search on a marine parts website, you may find an all in one wrench. I know a guy on a different forum has one. I bought the huge Mercruiser socket from a site in MI. Then I bought another socket at my local farm supply store to remove the outer nut. The front prop nut is like 2 1/8". I know there are trailer bearing sockets out there that are that size., My dad made his wrench from one of them.

 

[Don S]

Re: Exhaust Soot in U-Joint Bellows - '96 B III

A tuneup is something that should be done yearly (each spring) to keep the engine running at it peak. Might also check the choke. If it's too tight, it will cause a lot of excess smoke and takes a Looooooong time to come off.<br /><br />You can get a prop wrench at http://www.properthing.com/models.html look at item B3 Dual.

 

[TilliamWe]

Re: Exhaust Soot in U-Joint Bellows - '96 B III

I agree with DonS about the choke. Friend has a 7.4 that just rolled smoke for two years. Finally, another guy at the harbor, adjusted his electric choke, and viola, no more soot.<br />As far as soot in your gimbal housing, I have never noticed it in my 1997 B3. And again, I agree with Don, it could be something in the drive causing back pressure. Those flappers in the Y pipe could have fallen down and gotten lodged in there, I guess.<br />DonS, any chance that the solid rubber tube, that doesn't attach to the drive could be the problem?

 

[NoWorries]

Re: Exhaust Soot in U-Joint Bellows - '96 B III

Sorry, it's been a while since I've been able to mess with the boat or get on this site.<br /><br />Weather is still too cold to get the boat on the muffs (I don't want to winterize agin till October). I will definatly check the choke as that may very well be my prob. No signs of any restrictions using flashlight to look into every possible port. Maybe this is just an initail startup problem because my ujoint/yoke assembley has no soot at all.<br /><br />Was out tonight, greasing u-joints, coupler, new seals, and looking at the soot problem again. I noticed there is no seal to elimate water entering into the u-joint bellows. In the picture, the "Black to grey is where exhaust soot is collecting" arrow points to the mating surface for the drive. Is there not a seal or gasket on this mating surface either? With my pre alpha, there was a large gasket that surrounded the whole mating surface.<br /><br />Sorry for the Newbie questions, but it just seems the Bravos don't have enough gaskets to be surrounded by water!? If there is no seal for this either, what keeps the water out?