clutch get stuck why - bravo one

[Jacek]

Cone clutch get stuck on forward gear in one of my bravo leg (1:5) why ? It is wrong handling with gears. I don't know see the pictures below how dirty is gearbox full of remains of painting (have you ever see painting inside the gearbox ? what for). To detach we had to use hub puller and heavy work with hammer.
Regards:
Jacek

[kubcat]

I have a pair in my Cigarette and the Bravos are not the strongest drives for high torque applications. Bravo X drives (diesel version) are a bit stronger and then there are a few higher performance versions.

They need regularly changed Mercury high performance lube oil as a minimum and a drive shower is strongly recommended. With my limited knowledge, I am guessing the oil has broken down through heat and not done its job.

The size of the motors, year of manufacture, hours use and boat weight all play a major role. What are your specs?

Mercury has Bravo 2's for heavy cruisers with much bigger gears but they have different size props and are not suited to high speed.

There is a ton of aftermarket stuff to strengthen them in the US. Some good, some useless.

A great source of information are the forums on offshoreonly.com This site is for high performance offshore boats and almost everyone runs Bravos with huge levels of horsepower. Just remember when they quote horsepower it is on petrol high revving engines. It is torque that breaks them, so if you want to be in the ballpark i suggest you double the horsepower of your diesels and them you will be in a similar torque level for comparison purposes. There is a guy called arctic friends or something similar that is a wealth of knowledge, use the search function on the site.

[Jacek]

Kubkat thanks for information! I'm very caution about maintenance and change oil regularly rather is not the issue but other site bravo1 has no oil filter and circulating pump - old oil work in gear box down and fresh in the tank no mixing. This boat is 2009/2010 commercial use my set up is 2xCummins QSD 2,8 230HP each, boat 9m Parker 3,450kg empty (av. 3.700 kg with fuel), prop 22" (bravo one - in my opinion a little to big but gives 41kn top speed), 570h use, bennet tabs. Picture below.

[kubcat]

I have Yamaha Hydradrives in one of the boats and Mercruiser Bravos in the other.

The Mercruisers are very agricultural in comparison. Not necessarily a bad thing.

I am by no means an expert all I can do is share what I have learnt from having sterndrive boats for the last 15 years.

Just a few thoughts:

With the Cummins engines the drives are at the top end of their rating and you may need to exceed the manufacturers service guidelines by more regular gear oil changes.

Long runs planing will make the drives overheat as the oil does not have a pump to circulate it, the top gearbox is out of the water and the exhaust may run through it depending on installation. Black oil is a result of the oil breaking down and that is either bad quality oil or heat. A drive shower is a cheap, simple and effective solution to cooling Mercruisers drives when on the plane. If you don't have antifoul on the drive, the paint on the top gearbox is probably discolouring and looking a little gray or whitish from the heat.

Another cause of heat is if the shift cable is out of adjustment, even just a little, the clutch will slip a touch as you cruise.

Oil changes seem to be at the 25 hour mark with the high performance boat guys. Not sure what you do yours at or what Mercury recommends.

If your exhaust runs through the drive and the drive showers doesn't cool enough, you could look at having a separate exhaust pipe instead of through the prop.

[Jacek]

I thing that your premonition was correct - shift activator is broken (faults started appear on vessel view) and I had to change on new on this leg. Three months ago started appear faults form time to time. Service man did something - clean the pin but after that I realise that gear on this leg go with lag. Again I call service man and he adjust shit cable and week after that clutch got stuck! What do you think could be this cable adjustment the reason on stuck ?
Is seems that that was one of the reasons, second would be oil my service recommended oil changes every 100h. Now cut it by half to 50h and should be good.
Separate exhaust - also I've to adopt it.
Thanks for you useful advises!

[kubcat]

If the clutch cable is incorrectly adjusted or something is broken that makes it out of adjustment, it could be like driving your car with your foot resting on the clutch pedal. That tiny little bit of slip creates heat which burns the clutch and the oil.

Every 50 hour oil changes sounds like a good idea.

[Jacek]

Thanks a lot! Service told me that has nothing in common
Last question, in your opinion is possible use old unstuck clutch (after changing shift is ok) or I should put new set ASAP ?

[kubcat]

I am not an expert with Bravos but the manual has specs on how much wear is acceptable.

Mercury did have a recall on shift cables about the year your boat was built, might be worth a look.

http://www.ishopmarine.com/ishop-cat...2010/EN_11.PDF

[Jacek]

I've got! Many thanks!