Mercruiser 496 HO and Bravo sterndrive

MapisM

MapisM

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Is there around some experience/knowledge on this engine/leg?
I'd appreciate views on its usage, maintenance, things to check...
Any recommendation and suggestion is more than welcome.
Ta!
 
Excellent package, having the benefit of closed cooling means a long engine life and less maintenance. No real problems, lazy and effortless power suits high performance sportsboats and ribs best.

I had my first one 9 years ago, and have had several in various boats since, a real improvement on the old 454/502 MPi, with cleaner smoother running and much better fuel consumption.
 
Sleek and fast - 60 kts WOT at 5k rpm.
I wouldn't expect the type of hull to affect that much the engine performance and behaviour though, as long as it's properly sized, propped, etc. And as long as it's used similarly, of course.
After all, it's easier to push it hard on a heavy cruiser with a short prop and a relatively low speed, than on a very fast boat. Unless used for racing of course, but that's another league, where blue engines belong.
Glad to be corrected if you have reasons to think differently.
 
Just being inquisitive................... don't know anyone personally with the set-up, but have noticed they use them in ski-race boats to larger cruisers, obviously with different gearing and prop size.
I do like a well maintained V8, car or boat, such a sweet sound and great torque!
 
A beautiful sound........ As I was playing the Y-Tube clip, I turned up the sound and my wife came into the room thinking the boat was running in the back yard! :)
 
496 Mag HO

Mapis, I have 370 hours on my 2005 now. The drive is a Bravo 3X. 27ft Cobalt 263.

The engine or drive have never let me down. I have had it serviced by the book, annually with an oil change mid season.

The boat is fitted with a switchable exhaust system, straight though the transom or though the prop, I have never used it, the sound is intoxicating!

I have "Smartcraft" fitted, mainly to monitor fuel, but it is well worth the £80.00 investment. We cruise mainly at 28-30knts, burning 12-13 US gallons per hour. Wot is 5100 rpm, 51knts and 39 US gallons per hour, spinning a 26P prop, one of the best ways to spend an hour I get.

I try not to run at WOT for any length of time, maybe 10 minutes max and then a cool down, my mechanic has warned me that the previous Bravo drives get hot and evaporate oil, although the 3X (made initially for diesel) seems to have cured this problem.

Let me know if you have any other questions.
 
Mapis, just remembered, when the leg came off at the end of last season the oil was found to be contaminated with swarf.
Following an exchange of emails and pictures between my mechanic and the factory, Mercruiser paid for the gearbox to be rebuillt. It was decided that the pinion gear had been incorrectly seated during manufacture. The engine had 310 hours at the time and other than a slow shift that I had down to a stretched cable, I wasn't aware.
 
JamesTT said:
Mapis, I have 370 hours on my 2005 now. The drive is a Bravo 3X. 27ft Cobalt 263.
...
Let me know if you have any other questions.
Click to expand...
1st of all many thanks JTT for your very interesting reply.
Indeed you're making me curious about most of your points.
1) oil change mid season: Is that just to stay on the safe side, or what? According to scheduled maintenance, it should be every 100 hours or annually (whichever occurs first). And considering the year/hours of your boat, you don't seem to log more than a hundred hours/year, on average.
2) transom exhaust: never used it after 4 seasons? LOL, u must be joking!
The sound is definitely rude, but it shouldn't be so annoying above 40kts or so, unless cruising with a strong tailwind.
Besides, I read that this engine "suffers" a bit when running at high RPM with prop exhaust, because of the higher backpressure. I even found recommendations on US forums to use it ONLY with straight exhaust above 4k RPM or so.
OTOH, you seem to reach an already high RPM at WOT... Which leads me to the following point.
3) Are the 26" props the original ones? It's unusual for a builder to install props allowing the boat to go above the maximum rated RPM of the engine (which is 5,000, in this case). I wouldn't be surprised if you could see another 2 to 4 kts with slightly longer props and opening the transom exhaust.
4) Smartcraft: that's very interesting, I expected it to cost much more than 80 quids. Does it require just fitting the display somewhere on the dash, run the cable to the engine and plug the cable to the connector, or is it more tricky?
5) 10 minutes? Wow, and you call it not running at WOT for any length of time! You're covering 8+ NM in 10 minutes, at that speed! When do you find conditions allowing that!?
Re. Bravo III "X" version, I'm not sure if they were initially built specifically for diesels, but basically X and XR are stronger versions compared to standard drives, which are rated for 400hp. In fact, X and XR are rated for 450 and 600 respectively.
More about their differences in this table, if you're interested.
Anyway, it's true that Bravo drives can suffer heat problems when used hardly. For this reason, for high performance boat applications, sometimes showers are mounted on the drive. They're aftermarket accessories, made of a steel pipe picking water from under the cavitation plate and pouring it on the drive head. But I never saw a shower installed on a B III drive, only on B I drives of very fast boats.
 
Hi Mapis, the boat is lifted mid season primarily to check/change the leg anodes and for a scrub and wash off. Having the mechanic there I get an oil change done and have him check the drive/ engine over.

Sorry for the confusion, the exhaust is nearly always routed through the transom, the noise is too good to miss!

The props supplied with the boat were a 24P set, these did result in the boat over revving regularly when light and also a tendancy to cavitate in tight turns. The 26P set in my opinion is better suited to the boat. There is a lot of gear stored on board and with a full fuel and water load together with passengers the max rpm is usually between 4800 and 5000rpm. 5100rpm is only achieved at the start of a season when the boat is light from it's winter storage, freshly antifouled and before the tanks are filled. I suspect that the props are fitted in the UK by the dealer as are the batteries, although I am not sure.

We are fortunate to have, within a 20 minute run over open sea, a long ribbon stretch of tidal water known as the Menai Straits which seperates the island of Anglesey from Wales/UK, it is very sheltered and for much of it's 15 mile length unrestricted, a fantastic stretch of water which varies from about a 1 Km in width to less than 100m in places.

We fitted a Smartcraft SC 1000 multi function monitor into the dash in the position of the standard trim gauge. The monitor dispalys the trim as default whenever the trim switch is activated. It was bought in the US for $110.00 including a cable that plugged directly into the engine. My dealer installed the cable and guage and I set it up, quite simple, plug and play, but a fantastic tool for establishing an accurate range during different conditions as the total fuel used since reset is also recorded along with fuel flow.

The B1X drive came standard when my boat was built. I believe that this is a faster set up than the B3X drive but I wanted the added security of the grip of double props in the marina.

What boat are you looking at with this engine?
 
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