Slippage?? - Help!!!
 

I've been plauged with slippage issues since putting in my new engine this spring. Admittedly, this 540hp engine is way to much for a stock Bravo 1, but I haven't even gotten on it yet at all.

I first noticed that I couldn't go faster than 60mph. I'd get close and it felt like the engine was losing power. Couldn't figure out what was going on until one day I was trying to come on plane with a full load of people and the engine went straight to 5000rpm. I got off it, but couldn't get it back on plane until I let it sit for a minute then gently got it on plane.

At first, a friend told me it was a blown coupler. It's a new coupler and my engine builder (Tyler) said there's no way it could be bad and that it was probably a slipping clutch in the trans. I talked to a few more people who told me Bravos have separate forward and reverse clutches and that if I ran a LH prop, it should run fine in reverse.

Did that and it seemed to run fine (gently loaded), until yesterday when I had another heavy load and again it started slipping. Not as bad as before, but it did keep slipping to some degree until I let it cool down again.

Do Bravos have separate forward and reverse clutches? If so, what's the chance the reverse clutch could go when it's never seen heavy loads?

Could it be the coupler? Do they go like that where they'll recover a little when they cool down?

Any ideas? I'm really trying to nurse the boat through the summer and don't want to tear everything down without having some idea what the problem is. I could buy a new Bravo, but that won't do me any good if it's a coupler, and tearing the engine out to replace the coupler is a big hassel if that's not the issue.

Thanks

It cannot be the coupler it would have melted in a minute. Your bravo has a cone clutch, one piece for both gears. Mercury was upgraded them since your boat was new. Since the clutch engages the beaing and has been slipping all your surfaces are going to be blued and thus ruined. Your should find someone to rebuild your upper housing
Jim

Great, anyone in Michgan have a used Bravo 1 that would get me through the season?

Talked to John at Dollar Offshore this morning and he says that it sounds like the shift cable is out of adjustment. he asked if I checked the drive oil, and I had and there were no metal shavings and no burnt oil smell. He thought if I took the drive off and adjusted the cable, I might be fine for the season.

Anything that could slip in a Bravo 1 setup would end up being semi catastrophic, resulting in an almost total, to total loss of power. You can idle with a spun coupler and maybe even with wrecked gears. Your cone clutch, which is one part with 2 engagement surfaces, would probably weld itself to where you can't shift it anymore before slipping. It would definitely have a problem shifting into gear if it was spun. My vote is to check your prop hub. It could even be as simple as prop blow out. When you significantly increase power, sometimes the boat will act differently with the same prop. Just some thoughts,

Rene

If it slipped in both rotations I don't know how it could be an adjustment. If the cable is bad it may have contributed to the problem. Check the cable outer cover where it connects to the bellhousing in the mid section, often the outer part fails were it connects the the brass end. If it slipped enough to get the clutch and gears hot you will be extremely lucky to fix it with a cable adjustment. Good luck
Jim

I've tried 4 different props now. All do it to some degree, and they slip at speeds/loads where the secondaries aren't even open yet. The thing that gets me is that it recovers if I let it cool down. I can shift in and out of gear no problem around the docks, and as long as I'm gentle getting on plane and don't go fast, it runs like a champ. As soon as I get a little slip, it just keeps slipping until I stop and let it cool down.

Yeah, that's what I was thinking, but I'm at a loss for what it could be. The gear lube looks great, with no burnt smell at all, and it keeps recovering when it cools down. Sounds like everyone agrees it's not the coupler though??

Check the cable in the mid section if the cable fails at the brass you will lose travel, and make sure where it connects on the shift plate is tight. On the shift plate there is an adjustment slot. Unlikely but maybe the post is sliding in the slot.
Jim

Bravo's don't "slip" like you are explaining it. It does not have a trans and the cone clutch is is part of the shifting system. It sounds like a coupler or prop hub.

BTW, 540hp will not kill a Bravo if you drive it right.

It's not the prop hub, as I've tried 4 different props. Are you saying it could be the coupler then? Could the coupler start to slip then hook back up again once it cools down?

When you say "cable fails at the brass" Where should I look? Sorry, I'm pretty mechanically inclined, but new to drive terminology. Can I check it with the drive and engine in?

thanks

Would it be worth a try to extend the travel of the cable at the bracket arm and see if this helps? Could it hurt anything more than I've already hurt it (probably sliped it 8-10 times now)

If you turn the wheel hard left, trim drives up most of the way and look in the gap for a black cable, forward it passes into a bellows then in to transom. look aft where it enters the bellhousing " the part the drive bolts to" ,it has a brass fitting which threads into the housing. Very often the cable wears out there. The inner shift cable the cable just described is a 3-5 year service item. If that cable is bad you will lose travel. When you replace the cable there is a tool and a specific dimension to set it to. It should not ever need to be adjusted unless something is going away.At that point adjusting it treats the symptom not the problem.
Jim

Possible but not likely that it would continue to it on several trips out.

What prop are you running???? Sounds to me like you are just blowing out/cavitating the prop when you have a heavy load.

So far I've run a 25p Stilleto 3 blade, a 24p Stilleto 4 blade, a 23p Bravo 3 blade, a 17p LH (to try LH), and now a 25p Bravo 3 blade LH.

It does it at 60mph at a little over half throttle or coming on plane with the secondaries barely open (less load than the stock 330HP 454 put on it).

This weekend, once it happened (just a split second at 5000rpm before I caught it and backed off), even after backing off, I could barely stay on plane at 30mph 3600rpm. Once I let it cool down and brought it back on plane (same load in boat) I ran 15 miles at 45mph at the same rpm (3600) with no issues. The intial slipping (30mph at 3600rpm) was barely into the throttle at all.

I can't imagine prop cavitation could be variable like that. Especially at really low load. But I'd be willing to try anything at this point. Just talked with someone about buying a recently rebuilt drive. I guess it doesn't hurt to have a spare drive around, but I'd sure like to figure out the source of the problem before I start pulling the boat apart in the middle of our 10 minute long summer (Michigan)

And yes, it's now done this on quite a few occasions. Everytime, I think I've got it figured out and a week later it happens again. It is getting worse everytime it happens. Got better when I switched to LH prop, but I'm sure it will start to get worse if I keep running it this way.

Thank you, very descriptive. I'll pull it out of the water and take a look.

Never rule out prop problems. I ran 3 blade Mirage +'s with boat stock. Then procharged it and I could not get any of the Mirage +'s to hook. I thought I broke a top gear again, but was okay. I had solid hub props so I knew it wasn't those. Checked coupler and that was fine.

Threw a stock Bravo (4 blade) Prop on it and wallah - no more slippage.

Was really frustrating to have to come back to almost idle for prop to re-grab and then try again. Sometimes turning at speed would make me cavitate where I'd have to come back to off idle.

Really sucked !!!

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Not saying this is your problem, but I didn't believe it either - I tried it after checking coupler instead of before it. Live and learn. Doh.

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Possible drive shower or thru transom water pick-up causing your prop to cavitate ? I've heard of this happening but personally have not run into this one yet.

Is it possible to have some kind of disturbance in the water leading to the prop (air bubbles) ? Sure sounds like blow-out to me too... I had a similar problem but with TRS and cleavers.

With your latest description it really sounds like you are blowing out props to me. How big in diameter is that Stilleto 4 blade? You have a lot of small diameter props from what I gather. Try a Bravo 1, 4 blade and I think your problem will disappear. When you say cool off, do you mean literaly wait for a temp to come down or just wait till the boat settles and then try again? If I start falling off plane and allow the prop to blow out on my boat, I have to bring it back to idle and get it back on plane again. Your drive trim can also play a role if you are trimming out too soon or too high. Some boat/prop combos are more sensitive to ventilating the prop than others. It really doesn't seem like you have a drive problem. It would have come apart as soon as anything slipped. Same goes for the coupler.

Rene

the 4 blade is a 13 3/4. I'm no expert on describing this stuff, but I'd say the 4 blade bit way too hard. Seemed to be driving the bow into the water. Couldn't get the bow trimed up no mater how high I pulled the drive. I don't remember how bad it slipped. It was one of the first props I tried. Maybe I'll give it another try and see if it's better or worse as far as slip is concerned.

I did install a drive shower with the engine upgrade, but the pickups are significantly behind the prop.

Once it starts to slip is does actually need to cool. Just taking it off plane won't do it. Tried that once and had to idle two miles back to the slip. Next time it happened, I let it sit for an hour and it came right up on plane.

Also, if it were prop slip, how would it keep getting worse? Prop slip was my first assumption as well, but after this many props I gave up on that assumption. The drive is very deep (as they all were in '93) so I'm really struggling to figure how all these props could be ventilating. Again, who knows though.

This weekend, when it started to slip, I had my tabs about 3/4 down and the drive all the way down. Once it came on plane, I laid into it very gently, maybe half throttle, and wham, 3000rpm to 5000rpm in a split second

The only prop I haven't tried is a 25p cleaver. I guess I could give that a try. The 25p bravo I have on it right now runs fantastic when it's not slipping. Smooth as silk and an extra 5 mph more than any other prop I've run (effortlessly at 4000rpm)

I'm going out there tomorrow. I'll make it slip on purpose and try coming off plane to idle. I'm almost positive I did this two weeks ago, but maybe I never came to complete idle.

You need to try a Bravo 1 prop. Start with a 24 pitch.

Tabs way down will will keep the bow down, but will lift the stern and thus make the prop blow out easier.

The 4 blade you tried is to small of diameter and is a stern lifting prop.

Well, if you go with the prop slipping theory, Have you installed anything on the hull like a water pick up, any type of thru hull fitting, or transducer? As far as the clutch engagement theory goes if thats it, it will certainly give up for good soon. I hope you find problem soon.
Jim

If your props are an older style with the rubber bushings you very well could have a spun hub. You refer to your 3B props as Bravos but I am assuming that you are referring to the drive style. Are your 23P and 25P 3B props Quicksilvers or Mirage propeller models? If so they have rubber bushings and you should have them checked out.

Julie

Sorry, the ones that I refered to as "Bravo" are Mirage's. Could a rubber bushing go then hook up again once it cools off? The latest one I just bought off a member and it's in great shape. He had it reworked if I remember correctly and I have a hard time believing it (and 4 other props) all have bad bushings.

I think what the other posts are refering to is the prop actually ventilating or whatever, and losing traction in the water. I'm having a hard time seeing how a 23p Mirage and 25p Mirage could both be ventilating that badly with such a deep x-dim and half throttle. My application seems like exactly what those props are designed for.

SB referered to a 3B he had that would lose bite and then never recover till he came off plane. How does that work?

Thanks Julie

I can't begin to tell you how bad / horrible it was.

I'd go simplistic at first trying to diagnose youre issue. Put last years prop on and take the drive shower off. Just to try of course. Everything will be same (other than motor) when it drove correctly.

If it now works, figure out if drive shower (supposedly this happens to some people) or prop.

If it doesn't work, have a solid hub prop handy. If that doesn't work, well......it's outdrive or coupler.

Can't imagine why either of these would act this way but many of us run into strange things that don't make much sense a little too often.

I went out and pulled the boat out of the water, checked the cable housing as recommended. Seemed ok. No fraying.

Then figured just for the heck of it, I'd try to band aid the issue (assuming the issue was shift cable related) by increasing the pull on the shift cable by moving it up in the slot. When I measured where it was, it was at about 2.5 inches from the fulcrum (at the bottom of the slot). The manual says it should be around 3 inches. Went to adjust it to 3 inches and it appears it was only barely tight. I think it must have been gradually slipping down towards the fulcrum over time.

Put it back to 3 inches and couldn't get any slip, even at WOT. Didn't have a full boat load of people, but I got into it with tabs down, tabs up, drive down, drive up, and couldn't get it to slip the way it had before.

I'm guessing that with all the sliping it's done to this point, the cone clutch is probably trash. On Monday I went ahead and ordered up a rebuilt drive anyway. I'll put it on and rebuild this one as a spare.

Figuring at mid way through the summer I'm not going to have any luck finding someone to change drives in a timmely manner. How difficult will it be to change myself? Anything I should watch out for? Any threads with specific instructions?

Thanks for everyone's help!

Glad you found it and thanks for sharing your info. Yet another pesky problem poss. solution to put in our old grey matter.

Sorry, but this doesn´t add up, for me. The throw issue on the cable sounds like you´ve found something, but I wasn´t aware that you can get a bravo to slip like that.

You mentioned in one of your posts that the 4 blade was a 13 3/4".

With 540 hp (or even 150 hp less) on a 4500+ lb 25 foot boat, you should be running 15 - 15 1/4" diameter props.

A smaller diameter pushing this size of boat will slip.

A Bravo drive won't slip like you are describing. It does not act like an automatic trans slipping on a car. It acts like a manual transmission. It is either in gear or its not. There is no in between.