As seen in Speedboat Magazine’s Nov/Dec 2018 Issue.

Bravo 1 Sticks in Forward

Dear Bob:
Is there any reason my drive would stick in forward? I can sometimes get it out using some force on the shifter, but sometimes I had to shut down the engine and then it shifts back to neutral. It shifts to reverse and back to neutral without any problems. It also appears to work fine once it is shifted into forward but won’t come out. This is a new boat to me, and I’ve only been out twice in it. It kind of did it the first time out, and then was a real issue this last time. Docking is really not fun. Here are the specs: Bravo 1, twin BBCs with B&M supercharger (circa 1989), hydraulic steering, drive showers.
Syd Crawford Poughkeepsie, NY

Being that your boat is a twin engine boat, one of the drives is using a righthand propeller, and the other one is using a left-hand propeller. The one using the right-hand propeller uses the lower in the drive upper for forward operation, and the other uses the upper gear in the upper for forward operation. The easiest possible solution for your problem is an adjustment to the intermediate cable that connects to the shift quadrant to the drive. There is a slot in the arm that will allow you to move the cable pivot point up so it gets more travel when it is shifted from the helm cable. A 7/16” open end wrench is the only tool needed. This might resolve the problem especially because it can be shifted out of gear with the engine off which usually is not the case. It is more likely a problem with the cone clutch assembly or the shifting fork in the drive. The cone clutch or gear may be worn to the point where they stick together. The older drives like yours are more prone to the problem you are having. There are two thrust bearings at each end of the upper spiral shaft that can fail. If they do, they deposit debris into the cone clutch which can also cause the problem. The two gears that are driven by the pinion gear have brass rings on them which actually wobble and need to be in proper time for easy shifting in and out of gear. It is also possible that the upper was not assembled correctly paying attention to the gear timing by the last technician that worked on the drive. If you remove the upper plug, which should have a magnet on it, and you find silver flakes on the magnet, the indication is that a bearing or gear is beginning to fail. The bottom line is that you are probably going to have to rebuild the upper on that drive as a cable adjustment does not solve the problem.

Valve Seals on Iron Guides

Dear Bob:
I did not get to ask you a question at the Lake Cumberland Poker Run last September. My brain flatlined after you backed that 46′ Outerlimits into the slip (fantastic-nothing like a little pressure. I watched the owner step out while you took over). I called you a few years back
when I was replacing the valve springs in my 500HPs in a 35 foot Fountain. You said to remove the springs on the exhaust valve stem seals so it won’t use oil. Why? What’s the theory behind this? I’ve been a tech almost 40 years now and have done my share of engine rebuilds. But I never omitted the valve seals or removed the springs from the valve seals. I am interested in how you figured this out.
Mike Mason Cincinnati, Ohio

You must have misunderstood the reason I stated for leaving the springs off the seals on the exhaust valves. It is actually the opposite. Leaving the spring off the seal causes a little oil to leak by the seal which in turn lubricates the exhaust valve guide. This is something that we have done for years. Mercury Racing included the procedure on their performance engines with iron heads. It is only necessary when the heads have stock iron guides. As the exhaust valve temperature rises, it can stick in the guide because of the moisture present without a little lubrication. It is not necessary or desirable to remove the spring from the PC seal if the guides are bronze or have bronze liners. In every case when we rebuild an iron head, we install K-line bronze guide inserts and omit the procedure of removing the springs from the valve seals. The bottom line is that a little oil usage is better than having a valve stick in the guide.

Aerators on a Bravo?

Dear Bob:
I have a twin engine 32’ catamaran that has naturally aspirated motors with Bravo XR drives. The engines do not seem to have enough bottom end torque to get the RPM up to get the boat on plane in a reasonable amount of time. I have seen boats with these hoses coming from the drives that I am told were for aerators to free up the propellers when coming on plane. Is there some sort of setup that could be used on my XR drives?
Jason Joyce Atlanta, Georgia

Hi, Jason. Unfortunately, there is really no way to put aerators on a Bravo Drive. Aerators are designed to be used on drives with surfacing propellers. We make them for Mercury Racing IV, V, M6, and M8 drives. We also make them for the Indy drive. Normally, depending on the application, drives with surfacing propellers are installed at a height that results in about one-half of the propeller in the water when the boat is under way. Most performance catamarans have the prop shafts a little higher than vee-bottoms. The aerator incorporates a tube on the underside of the cavitation plate that is positioned so the leading edge of the propeller sweeps behind it close enough to draw air into the propeller. The cavitation plates on Mercury Racing M6 and M8 drives are hollow. Because of this, a hole is cut in the top of the cavitation plate and a mount is installed that has the hose connected to it that extends above the water line when the boat is at rest. When the drive is placed in forward gear, even at idle, air is pulled down the hose and into the propeller causing it to slip more. This is beneficial for getting the boat on plane as well as easier shifting and handling around the docks. Once the boat is on plane, the aerator is no longer in effect except if extremely rough conditions when the boat lands and buries the drives. In this case, aerators help take the load off the propeller and engine and result in a quicker recovery. Aerators are especially beneficial on higher powered boats that have higher gears and high pitch propellers. In use, aerators sort of create the affect of shifting gears as the boat goes on plane. Aerators are almost a necessity on boats with turbocharged engines because it allows the engine to get up to RPM quicker which results in the turbochargers being able to spool up. The effectiveness of the aerator can be adjusted by how close the tube on the under side is to the leading edge of the propeller. For maximum effectiveness, the tube should be about 1/4” from the propeller. If the aerators are working “too good,” you can iincrease this distance for the desired effect. The photos show the typical installation on a Mercury Racing M6 drive.

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