Inspecting TRS/TR outdrive

EMTJEEP

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Now that I finally got my boat (1977 ThunderBird F20-CL with a GM350 280TRS) running after the previous owner let it sit for the past 20 years I am going to be moving to the drive to inspect it and repair any parts and seals that need to be replaced.

My question is what would be the best approach for inspecting the drive?
 

Bondo

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after the previous owner let it sit for the past 20 years

Ayuh,.... Ya probably oughta tear it down, 'n reseal it after sittin' 20 years,.....
 

alldodge

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+1 agree, going to need some special tools to reseal. The housing are in demand because in you hull type are faster then a Bravo. Parts can still be purchased but not the housings.
 

EMTJEEP

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It's just the six bolts holding it all together so it shouldn't be too hard to remove. Any special things that I need to do while taking the drive off? Mark the driveshaft so it goes on the same way it came off or anything like that?
 

alldodge

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Mis-spoke in my first post, I mixed up the TRS drives with the Blackhawk drives. The TR/TRS are good drives but not in the same demand for extra speed. All the same just remove the bolts as NHGuy mentioned and it should slide right out
 

EMTJEEP

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NHguy I got an engine jack that i am going to use and already have that section of the manual printed out and read it a couple times.

As for which drive I have, how do you differentiate between a TRS and a TR-II? Also on the picture where the red circle is there was what looks like to be a little cover piece but it is no longer there and now there is just a hole. Do I need to plug it back up and if so what is the best way of doing so?

 

alldodge

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I'm not NHGuy but I'll provide the following:
The red circle was just a plastic cap covering a hole leading to a bolt which holds a zinc for corrosion protection

Here is info on the TR/TRS drive found at OSO
http://www.offshoreonly.com/forums/general-q/33438-mercruiser-tr-2-a.html
There is the Mercruiser II drive otherwise known as the Mercruiser TR (Transmission) drive. The Mercruiser II TR swings a very large prop for houseboats, work boats etc.

The Mercruiser II TRS drive (Transmision Sport) drive is the same as the TR but has a shorter lower gearcase that swings a standard size prop. Almost all Mercruiser II drives are of the TRS design.

The Mercruiser II TRS is a very nice drive but was expensive to produce because it required a separate transmission between the engine and the drive. The transmission also moved the engine ahead another 15 inches taking up more space in the boat. Some came with a Borg Warner Velvet drive transmission that is hydraulicly shifted like a modern automotive trans. The trans is capable of withstanding high horsepower engines (it is also used in racing Super Speed Master drives) and shifts very smooth.

To reduce costs Mercruiser built there own transmission and installed them in lower horsepower Mercruiser II TRS drives. This low cost trans was made from the internal parts of a Ford C-6 automotive transmission, had very small input and output shafts and was very weak.

The TRS outdrive (upper driveshaft housing and lower gearcase housing) is very strong (much stronger than any Bravo drive) because it is a straight gear drive (no trans in driveshaft housing) with helical cut gears in the upper and lower.

The weakness of the Bravo drive is that the transmission is incorporated in the drive shaft housing and the lower gearcase housing has straight cut teeth gears so a reverse rotation drive can be obtained by running the drive backwards (simple changing the shift lever linkage). The Bravo is a compromised drive for engine compartment space and manufacturing costs compared to the more expensive and higher quality Mercruiser II TRS drive.

The Mercruiser II TRS drive with the BW Velvet Drive transmission will easliy accept 500 horsepower. The Super Speed Master II is the Mercruiser II TR with a high performance lower gearcase. The advantage to the SSM II gear case is that it is smaller in diameter, longer and pointed without through the prop exhaust. The SSM II lower gearcase was faster through the water and wouldn't "blow out" at high speeds. These lower gearcases are no longer being manufactured by Mercruiser Racing. They are not any stronger than the TRS lower gearcase (strength was compromised for a smaller diameter bullit).

I really like the Mercruiser II TRS drive with the Borg Warner Velvet Drive trans and most of the parts are still being manufactured by Mercruiser.
Because of the extra cost they were usually installed in more expensive boats and are not very common. If you have one hang on to it!

Sincerely
Dennis Moore
Mercruiser Master Tech
 
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