Markings inside BF100 BF75 gear case housing? "TB1" and one has none at all????

While doing work on my BF100 gear case on the inside it has markings TB1. In the manual I found the refrence chart that shows this is the code for what sim/washers are used.

On my BF100 I have a noise when the gears are in forward or reverse but not in neutral. I am thinking it must be in the forward main bearing or the front prop shaft bearing as those are the only bearings not spinning in forward or reverse. The water pump shaft continues to spin in neutral and there is no noise in neutral so from the pinion up those should be OK. Correct thinking ?????

So thought I would just spend the $20 in new bearings and shims for the prop shaft. To find out what shims I have no markings on the inside of the housing. No markings mean anything or will I just have to get a caliper set out and measure the shims before ordering new ones?

Thanks for the help!!!

Well, this is an area where the shop manual really lets us down in that it doesn't give any clear direction as to what the clearances in the transmission should actually end up being.

You start off by saying you found markings inside your gear case....T B 1....then later you indicate there are no markings. Which is it?

The mainshaft (or pinion shaft) spins constantly in gear or out. The bevel gears are in constant contact with the pinion gear therefore they are also spinning any time the engine is running.

The only bearing NOT turning when the transmission is in neutral is the ball bearing in the prop shaft holder supporting the rear of the prop shaft.

If the noise is only present while the transmission is in gear, then I would either suspect the propshaft bearing OR the mainshaft thrust bearing. I would think it is more likely the prop shaft bearing. I believe the thrust bearing would be typically more heavily loaded only in forward gear but I may be wrong about that.

One other thing to suspect might just simply be the reverse gear or "prop end" thrust washer being excessively worn. I would measure that first...Here the book is not much help but it does list that washer as either 2.10mm or 2.15mm. If it is worn well under the the 2.10mm dimension, try replacing that before you do anything else. Also, note that it only installs one way and could have been improperly installed by someone else before.

I think the markings listed inside the case are for setting up clearances when everything is new. Since you're working with components that are ALL likely to be fairly well worn...I'm not sure those shim and washer sizes would help you arrive at the "correct" tolerances anyway. The book is not of much help in this area so trying to snug one up without getting things too snug will probably involve some trial and error to achieve.

Two motors. One has the TB1 and runs very smooth with no issues. The other is making the noise and has no markings inside the gear case.
Sorry for the confusion.

Some castings have an identification to indicate what mould they came from.---------Helps the factory in case of problems.-----They will know which machine is spitting out the defective parts.

Ok, I guess it was in your "headline"...I just didn't put it together.

I would still look at that thrust washer "behind" reverse gear. To do that you will need to remove the prop shaft holder so you can inspect that bearing at the same time.

I hope it's as simple as that.

Good luck.

Thanks for the help. I just scored a deal on Ebay for an entire lower end with short extension case. Has everything from the top of extension case down including drive shaft, shift rod, water tube, and even the prop still attached. $80 shipped complete unit. This will allow me to swap out the entire lower end and turn my long shaft into the short shaft I want. Its off a 80's motor with CDI so should also have the impeller and shaft that doesnt use the key pin water pump so new impellers are easy to find and cheaper as well.

Still going to run through this lower unit to find the culprit of my noise and will let you know what I find.

jgmo again thanks for all the help. Looks like with your help (and others on this forum) I am going to take 3 project motors and get them all up and running for this summer fishing season in the high sierra lakes near Tahoe

SO! You're the guy that OUTBID ME!!!


Ha ha! Just kidding!

Glad to TRY and help but you're doing all the work! I just sit here at the keyboard and sip my coffee.

Good luck with all that AND maybe boating a few trout as well! It all sounds like good, clean FUN!

So I dug into 2 different lower end gear cases. One is aBF100 (10hp) and the other a BF75Z (7.5 hp).
Inside the 10HP case I found the symbols squareA1. Originally I thought the square was a "T" and"A" a "B" as it was hard to read. Cleaning and usingbetter light showed the worn marks were a square and “A”. With that info I took a set of calipers and made measurements on all the current washers in the lower unit. My calipers are standard not metric so I had to convert and in the conversion looks like all the washers/bearings are very close to what they should be so in general that gear case is in good shape.

The 7.5 HP is a different story. It has no markings inside the case and some very worn washers/bearings. The entire reason for digging into this housing was when running it made noise while in gear, forward or reverse. Only in neutral would the noise go away. So with no markings and worn spacers I think I have found the combination of what should be in it. This is what I found and let me know if my thinking is correct.

metric to standard conversion for the factory parts options are:

Gear Shim Forward Gear - 2 choices of combinations A+A or A+BA .10mm= .003937
B .15mm= .00590

Thrust Bearing Washer (Pinion or driver shaft) 3 Choices
A 2.00mm= .0787
B 2.05mm= .0807
C 2.10mm=.0827

Thrust Washer (Prop shaft) 2 Choices
C 2.10mm=.0827
D 2.15mm= .0846



10HP case I found the symbols SquareA1. According to the manual that would be = to:

Gear Shim= A (0.10 mm) + B (0.15 mm). These are the shims for the forward gear bearing. My actual caliper measurements were .0045 and .0075

Thrust Bearing Washer “A”= 2.00 mm washer. This is the washer on the drive pinion shaft. My caliper reading was .0785

Thrust Bearing “1”= washer “C” (2.10 mm).This is the washe ron the prop shaft .082

Also on the prop shaft are 2 shaft washers. No listing in the manual for thickness but both were .058 on the caliper.

All these measurements and the conversion seem to point to good parts.

The 7.5 HP. So with no markings and worn spacers I think I have found the combination of what should be. Looks like itis the same as the 10hp and should have squareA1 mark. This is what I found and let me know if my thinking is correct to come to the squareA1 conclusion.

Gear Shim= A (0.10 mm) + B (0.15 mm). These are the shims for the forward gear bearing. My actual caliper measurements were .005 and .008. There are only 2 shims listed for this spacing and even though these shims were both corroded and worn down to ½ moon shapes I could tell one was thicker than the other. Conclusion is both an “A” and a “B” shim.

Thrust Bearing Washer “A”= 2.00 mm washer. This is the washer on the drive pinion shaft. My caliper reading was .0785 same as the 10hp that was marked “A”.

Thrust Bearing “1”= washer “C” (2.10 mm).This is the washer on the prop shaft. Caliper reading was .0823. According to manual should be a “C” washer like the 10 hp.
Also on the prop shaft are 2 shaft washers. One was the same as the 10hp @ .058 and the other was thin at .036 (worn and corroded).
With this info I think I found the correct shims for the 7.5 hp and at the same time think that replacing the worn/corroded shims will solve my noisy gear case in forward/reverse.
Sorry for all the numbers and hope all that isn’t confusing J

Anyone ever used the bearings off Ebay that are over 1/2 the cost of factory TOYO bearings?

You have NO idea how many hands have been there "afore ye" therefore....trial and error on gear clearances.

I have no experience with ebay bearings.

Good luck.