A week ago I became the proud owner of a 1968 Formula Thunderbird. It's the 19' Cheyenne cathedral hull and it's an absolute beauty. It's got a Mercruiser 160 with the Bravo outdrive. Put it on the water for the first time this past weekend and she broke my heart.
The engine started right up and ran like a top, but was having a hard time idling, but we let it warm up and got it in gear — both forward and reverse. After throttling up and roaring around the lake for about 5-10 minutes, there was a gut-wrenching grinding sound from the sterndrive and the motor quit. We could not get it restarted — it felt like the boat was stuck in gear.
Eventually, we got a tow back to the ramp and got it trailered. There was clean, whitish foamy fluid leaking from the side of the outdrive — coming from the horizontal seam between the two parts. A mechanic opened it up and said there was more water than fluid. The really frustrating aspect is that I can't find a marine mechanic that will work on it...
I'll try to get some pics and serial #s once I got get the boat from the marina, but any advice — from diagnosing the problem to finding a service technician would be greatly appreciated. I'm new to all this (boat ownership, fiberglassics AND the website) so please be patient if I've worded things poorly.
Welcome aboard Zbryant. Sorry to hear about your outdrive catastrophe, that doesn't sound good! (I have no knowledge on I/O's, but we do have some members here who do - I feel sure some of them will be able to help with info.) We'd love to see some pics of your boat and be sure to include some of the drive train.
Also, posting your general location will help in finding a reputable repair shop if you choose to go that route. Sounds like it may be cheaper to find a replacement drive unit (maybe a used unit off a donor boat?), but I'd sure check it out first.
Back in 1968 there were 2 inline 6 cylinder engines available.
One was a 250 CID rated at 160 HP like you state. It was mated to a MerCruiser #1 drive. That drive was used on the 120, 140 & 160 engines that year. Gear ratios were 1.98:1 for the 4 cyl and 1.65:1 for the 6 cylinder. There were no other choices for that drive in 1968. (There were no V8s mated to a #1 drive until 1971 when the 302 188 HP was introduced).
There was also a 292 CID rated at 200 HP and it was mated to a MerCruiser #2 drive. That was a huge drive, basically a predicessor to the TR and Bravo drives. The 200 HP 6 cylinder was only available for about 2 or 3 years and was not common but I would expect certainly an option on your Formula.
Other than its size, the #2 drive shares little with the Bravo unit.
If you do indeed have a 1967 to 1969 160 with the #1 drive, then the entire drive (top & bottom 1/2) shares a common oil chamber. No oil means damage up & down.
You need to shift the drive into FWD gear & remove the drive by removing the 6 nuts & washers & pulling straight back. Then find a mechanic. Your problem is that most mechanics don't want to work on the old stuff because they can get stuck for the repair. Basically, the repair will cost more than the boat is worth & they may get stuck with a customer unable or unwilling to pay the repair. Also, depending on if you are in a northern climate, customers that are able & willing will screw you until May. Personally, I would be hesitiant to take on the job. Some mechanics are not familiar enough with the old drives to know the interchangeability.
Early drives like that have some hard to find gears & shafts in the upper unit & the lower gears are not exactly the same as later ones either. If you have destroyed it, then you will be best off to find a doner junk boat. The drives from 1967 thru 1989 Alpha (generation 1) will all work. You need to find one with a 1.65:1 ratio. You will also need to verify that the drive shaft that goes to the engine is the short length. It must be the same as yours. If not, you will need to swap with yours. Since the 6 cyl 160/165 HP was only made up to 1979, you may find the drive & ratio you need mated to a 470/488 4 cyl and some V6 and V8s. V6, V8 and later 4 cylinder units used a longer drive shaft. If I was looking for a doner, I would look for 1970 and newer that has a tapered prop shaft where it comes out of the drive (unlike the square shouldered type you should have). Also, these units have a fine thread for the prop nut. They use more common parts easily available even today. Also, the unit is a bit stronger due to the longer support span the bearings have on the prop shaft.
WOW! i wish that i was still in Northern VA (rather than south TX), because i'd be on my way to Charlottesville for that one!
(I'll PM my younger brother-of-the-heart about it, as there are a LOT of "junk boats" with a #1 OD for cheap/free in VA/MD/DC.)
A Cheyenne is a NICE boat for the Chesapeake to chase Rocks.
Yes he does, that is a 292CID 200 HP 6 cyl. You can see from the 4 barrel carb, the taller push rod covers & the taller water hose from the tstat housing to the water pump. Also what is left of the HP decal on the valve cover is simply the last digit, in this case a zero which obviously has been misread as "160"
Someone has bastardized the ignition system with an automotive system. Parts for that old #2 drive are scarce.
Back in the early days of I/Os there was a fast evolution and things changed frequently. Serial numbers were important for parts.
It took 5 years until MerCruiser standardized the #1 drive (1967 model year) yet even that drive had frequent upgrades that were not obvious externally. The 2 biggest visual changes were the prop shaft I talked about earlier and the relocation of the trim lines from the sides of the transom plate to the bottom in 1970.
Does that answer your question at all - absolutely not because you have a #2 drive. They were much more rare and had all sorts of oddities. Things like "swivel" - yes swivel. What is swivel or optional power swivel? The early #2 drives swiveled. That is that with a big crank (or electrically w/power swivel) the drive rotated 180 degrees until it pointed UP, yes UP. That is the position you placed it in for trailering. The transom plate was huge and sort of diamond shaper. Later ones looked like your.
In this part of the country, the #2 (and even much more rare #3 drives) were typically only installed in houseboats & larger cabin cruisers. Very few runabouts had them installed. On the Mississippi we may still find a few, but that is over 100 miles away. They were expensive and heavy. Also, with the 20 inch diameter prop you needed an additional 4 inches of draft. Back then the OMC stern drive (electric shift) was available with 200 HP and was actually somewhat more common in the 20 to 25 foot range.
I have never worked on a #2 or #3 drive & I've been doing this stuff for years. We almost never even see Bravos here in Holcombe.
Sorry I can't be of any help with your #2 drive. Maybe Joe can offer a few words of advise.
I am sorry but I do not know of an easy, quick, and inexpensive solution.
I do believe that with a good search and patience, that just like your very nice boat and motor turned-up, that a used drive unit can be found. That said, the used drive unit will need to be inspected and resealed (at least I would if it were me), and this is not going to be as inexpensive as I would guess you would wish to spend.
Neither am I aware of a ready-made adaptor to exchange from the #2 drive to a #1 drive.
In the end (against what some people think of dealers), it is saddening how much damage and cost occurs from:
1): not checking or changing out lower unit and outdrive gear lube, with damage as has happened here
2): cranking and running motors without cooling water, or not replacing water pump impellers before long past their reasonable life, damaging engines, exhaust and cooling systems
3): operating with old, dead, water-laiden fuel, often then requiring engine fuel system rebuilding
4): test running engines with known rotten wiring, blowing unnecessarily costly ignition and charging components
I wish there was a way to stop it all!
Please feel free to write if you think that we may can be helpful somehow.