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Old 06 October 2021, 18:48   #21
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That's quite a noise from the drive, could you hear it from inside the boat?

I noticed your stand and sussed what it was, hopefully, I'll never need to duplicate it!

It's good you've got your bearings and gears set.

Edit: Just missed your last post by a few minutes, you've been busy!
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Old 06 October 2021, 19:49   #22
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That's quite a noise from the drive, could you hear it from inside the boat?
I popped it in reverse from the cockpit which loaded up the upper gear & bearings - so yeah, could hear that. Didn't sound bad in fwd and neutral though.

This is the setup for running it at home to keep things sociable.....
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Old 08 October 2021, 06:54   #23
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Nicely done. What were you original symptoms that prompted you to rebuild it? I'm currently running a pair of these on a 10m Novamarine tender - started off the season (after a previous rebuild) with slipping going into gear on one of them - I understand this is a widespread problem relating to lack of friction on the clutch cone. After a while that seemed to disappear which was good....however I still have the issue that one drive absolutely drinks oil (have to top it up every day). A busy summer season has meant no down time to get the boat out of the water and resolve these issues, but now is the time. Will probably hand them over to a Mercury engineer, but fascinating seeing how it's done.
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Old 08 October 2021, 08:00   #24
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Original symptom was bearing whine when I engaged reverse - there's a linky to a video of it further back I posted for jw.

Slow engagement (only on a bravo, alpha and outboards work differently) is one of 2 things: Maladjusted cable or worn clutch

Cable can be done inside the boat, you just need the little bracket to set up the neutral and throws on the gearshift bracket that’s mounted on or near the engine.

If it’s worn clutch, it’s usually fwds. On a bravo, they are interchangeable, you can swap your port and stbd drives over periodically to improve clutch life, especially if used commercially with high hours. You could swap props, but then you have aggro on the gearshift cables swapping them over too. Plus handling can change if you swap prop rotations.

ETA - with hindsight, poor shift could also be contaminated oil too I guess. I was taking it as read the oil is OK, but if it's not had an oil change for a long time - or there's water in it........

On the oil leak - Inevitably a seal, only question is which one. Reasonable chance it’s your prop shaft seal since that’s the one that gets fishing lines wrapped round it. Well worth getting sorted sooner rather than later though.

Easy to check/find - you can see the pressure test rig I have in the earlier pics.

WRT to a Mercury Marine Mechanic. There used to be a go to guy in Poole for rebuilding bravos - but he's now serving at her majesty's pleasure!!!
And I won't be going back to him once he's out, either. If you know who I mean, you know why.

When I asked round "the circle" for who was good on bravos drives these days, no names came up. Certainly there are guys I could recommend for outboards, but no-one for bravo drives any more (or even inboards generally). So if you have a good marine engineer who can do this for you properly - look after him!
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Old 08 October 2021, 08:15   #25
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On my one, I've made sure the clutch cone that showed more wear is now on the reverse side.

A new clutch is £472 retail. It's actually the only part in my upper that I didn't replace. However, easy enough to replace at a later date.
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Old 08 October 2021, 10:42   #26
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Minor suggestion re your press.
Drill a couple of holes through the base flange of the jack & bolt it down to the plate it sits on.
Stops it sliding about & if something suddenly lets go/breaks off when being pressed it stops the whole bottle jack coming off.
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Old 08 October 2021, 11:40   #27
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Good idea, thanks. It has a sleeve at the top, but nothing on the bottom. Don't actually use it that much, although it's one of those tools than when you need it, you really need it. Certainly made getting the new bearings on the pinion gear a lot easier than it would've otherwise been - mercs instructions on their installation are very precise.
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Old 08 October 2021, 18:49   #28
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On my one, I've made sure the clutch cone that showed more wear is now on the reverse side.

A new clutch is £472 retail. It's actually the only part in my upper that I didn't replace. However, easy enough to replace at a later date.
Thanks for the above advice. The boat is four years old, engines now have 1200 hours on them. The standard Bravos were replaced about two years ago with the XR model as there had been some issues with them. I've only had the "pleasure" of dealing with it since the start of this year (it's a tender for a larger motor yacht of which I am the skipper). I had a different understanding of the clutch issue to what you state above - previous skipper told me the issue he'd come across was the oil essentially "polishing" the clutch cone and making it too smooth which caused the slipping into forward that you mention. During the previous rebuild the existing cones were lapped to increase the friction which seemed to work for a while. He got into the habit of changing the oil every 50 hours which seemed a bit excessive to me. I was advised to fit drive showers to improve cooling as that might help - which I did. I've done the opposite of very regular oil changes and put 150 hours on since the last oil change which has actually improved the situation somewhat - could also be the showers helping or could just be fluke. But the issue of the oil loss is worrying me - agree with you that is must be coming from a seal somewhere. Our season has now finished until next year so need to get the legs off and rebuilt again. Boat is currently in the South of France so hopefully I can locate someone competent around here!
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Old 08 October 2021, 21:48   #29
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Something's obviously not right is it. What engine is it attached to?

A guy I know ran his boat with 900hp through an XR over in sweden.


I know of at least one guy over here whose drives date from the mid 90's. He had one let go during the august race this year - but it's had 600hp small blocks on it, now big blocks, and he's well known for not throttling. But still drives lasted from the mid 90's. My old formula was a 1989 boat and the drives were corroded to buggery - but they were still working fine. And a bunch of scorpion ribs had them in the UK. I know one guy broke an XR drive earlier this year - but he hit something and it chipped a gear.

Weak spots - if you over torque them, you can drive the clutch through the bottom of the gears. That's one of the things XR's had is thicker gear bases IIRC. But the straight cut gears are less refined than the helical cut ones - they are noisy. So they do offer XR uppers for some of the diesel packages on a B2 or B3 lower these days, too.

Drive showers? Certainly if you are turning the revs, you get a lot of heat buildup, which showers can help disippate. But the later models have a thicker, finned, cap anyway. I have a shower for mine, but I've never fitted it - I've not seen any evidence of it overheating, yet.

There are also some further upgrade options either from the bravo shop or max machine worx, or different drives from Imco. All still run the mercury gearsets though, I believe. There is the B-Max drive that is substantially bigger than a bravo - but not sure what gearsets & clutches that runs.

Sorry can't be more definitive with my answer - internet diagnosis is always a bit tricky.
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Old 09 October 2021, 18:11   #30
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All done - it lives again....
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Old 09 October 2021, 18:40   #31
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All done - it lives again....


Nice, we’ll done.
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Old 09 October 2021, 22:09   #32
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Looking good - it certainly looks a lot stronger than standard Bravo too!

Out of interest, are those additional steering arms connecting to the bottom of the gimbal ring? I was never a big fan of the single tiller arm at the top of the standard drive. What's the additional tube clamped to the trim cylinder too?
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Old 10 October 2021, 08:49   #33
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The single tiller arm on a bravo is a known weak spot. It's strong enough (the joke is that the pin is made out of kryptonite it's so hard) - but it runs in the aluminium gimbal ring which wears over time.

If you're buying a boat with bravos, play in the steering is a thing to check. It's a simple fix, you can just shim the steering pin to the gimbal ring - but - it's only simple after you've removed the engine, drive & transom assembly...

The usual upgrade is to fit external hydraulics - which can be full hydraulic or hydraulic assist. Either's good since it takes the load off the tiller & pin. This pic is my old boat - it had that problem and this was my upgrade, after I'd shimmed the tiller properly. Still had normal cable helm steering going to the transom, but instead of the internal hydraulic ram, I had these external ones.

This boat has Mercury's ITS system - which has a few features, including full external hydraulic steering built in. The helm is a hydraulic pump, not unlike what you see on a JCB etc. It's a really good setup.
https://www.forceboats.com/listing/m...ransom-system/


The additional tube clamped to the trim cylinder is a mechanical trim indicator. So as the drive goes in and out, it pushes that cable in & out to an indicator on the dash, that also has the trim tab indicators on too. See pic..
(The incorrect gauge has been replaced since that pic. )
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Old 10 October 2021, 18:40   #34
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Many thanks Matt, very interesting. I've seen the full external IMCO/Mayfair type of external steering before on various boats, but I'd never seen or heard of the ITS transom assembly until today - that certainly looks like a nice upgrade on standard that resolves several of the weak points.

Agreed, one of the first things I did when I bought the Ribtec was to rip out the tiller arm, steering pin, gimbal ring, etc,. and replace all of it with improved parts (where possible) from the US, to remove all the steering play. I still thought it was a weak design though and was eying up external options, but given I was cruising rather than racing it actually worked very nicely ever since and I never quite felt the need to change it all. I've swapped my standard Bravo trim sender at least once or twice too, so understood on the external trim sensor upgrade!

If I was buying a boat with a Bravo again, I'd definitely be looking at some of these options, so great to be pre-armed with extra knowledge :-).
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Old 10 October 2021, 19:44   #35
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Yeah, the imco stuff is nice isn’t it.

The original version of this was a bravo one x drive with imco steering, but then an ITS and sports master rig came available and it was a no brainer.
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Old 11 October 2021, 19:41   #36
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Interesting read
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Old 11 October 2021, 20:59   #37
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Thank you.
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Old 11 October 2021, 21:13   #38
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@Tim - 1200 hours. Given the high duty cycle of a marine engine & drive compared to a car, by my sums that's a not insignificant number. A friend's dad has just brought his Hardy back to the UK with 1600 hours on the drivetrain and it's starting to get a bit tired - that's on shafts.

And a friends Sunseeker Camargue 46 with 800 hours, again on shafts on was very due a rebuild (in fact, the stbd motor had been rebuilt already and was showing significantly more power than the port motor which had all the hours on it).

Other "factlets" I've found - the latest XR gearsets aren't as good as the early ones (boo since I've just bought a set) and the only benefit to them reallly is the benefit to handle more torque. They have no extra longevity as such, compared to an X drive. And in all cases, whether normal, X or XR, the clutch setup is the same I think.

Over on offshore only they most run bravo drives, they're talking as low as 250 hours between rebuilds on the XR - although this is more usually with supercharged big blocks and that type of thing.

At the other end of the scale, Merc quote a 525 EFI engine as needing a top end refresh at 100 hours I think - albeit it that's in their "race" range, not consumer. In most of the consumer range, it's usually corrosion, not wear, than ends an engines life. But even the folly ferry boats - it's always the gearboxes that fail on their ferries before the powerhead (I remember chatting with him about how many hours they get out of a motor a few years ago)

I'm afraid nothing definitive - I do my research, but just don't have the volume of drives I work on to confirm for any given setup's lifespan. However, one small nugget. For £1.99, maybe grab this : https://www.bottomlinemarine.com/pro...27t_9949.shtml

It is a definite that if the transom gear shift cable is out of adjustment, it'll be very lazy going into gear, which'll slip the clutch more. I know this since when I built my boat, I forgot to do this and could barely engage reverse at all. For £1.99, not much to lose!
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Old 12 October 2021, 15:12   #39
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A couple more things for longevity: Consumer leisure engines are rated for low power use, stick at or, preferably, below the manufacture's continuous power usage. Be sure the boat is propped correctly so as to ensure correct engine and drive load. Props with too much pitch overload the drive.

The faster the boat is travelling, the less is the load on the propeller(s) and, therefore, there is less load on the drive gears - from this, ease on the throttle up to speed, no gunning it!
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Old 12 October 2021, 16:12   #40
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A couple more things for longevity: Consumer leisure engines are rated for low power use, stick at or, preferably, below the manufacture's continuous power usage. Be sure the boat is propped correctly so as to ensure correct engine and drive load. Props with too much pitch overload the drive.

The faster the boat is travelling, the less is the load on the propeller(s) and, therefore, there is less load on the drive gears - from this, ease on the throttle up to speed, no gunning it!
The OSO crowd say the same - don't gun the throttle getting up and going, take it easy getting up onto the plane especially.

To further back up what jw says, if you look at the specs, the "commercial" spec for an engine is always a lot lower than the pleasure spec.

I checked the spec of the bearings in the (old) gears I've now replaced the other day.
They are a Torrington bearing rated to 3300 rpm. Which on the end of a 16/19 gear, at 4600 rpm (consumer typical redline on petrol V8s) = 3873. So beyond the bearing spec! It's all a laugh.

I think I'll be installing my drive shower soon.
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