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Engines are out and low and behold the gears are MG 502. We have 330's and this gear seems small. Has anyone used the 502 in higher horsepower applications? Does anyone know how much this little gear will take before giving up the ghost?
Don't want to go for new gears if we don't have to. Any help would be great.

JP.

I have a TD 5011A in my Searay behind a 350-375hp Chevy V8. The 5011A is the same "class" gear as the 502 / 5010 / etc. ...very similar. Both gears weight around 109 lbs and are 8" long from the face to the flange. I have grounded the boat, launched the boat offshore (on numerous occassions) hit a pipe line once, chewed a bunch of mud..sand, etc...not the first signs of any gear problems in 5 years of use.

I know the Chevy doesn't put up the torque that the Cummins will but the gear has had to survive 4,200 RPM... The Cummins will never spin them that fast....the wheel has come out of the water on occassion offshore with the engine turning 3,300 RPM...it QUICKLY hits 5,000 and the gear is what pulls it back it line once the prop re-enters the water.

Mine is a 1.9:1 and I run an 18x20 3 blade with a 1 3/8" shaft.

Don't worry about those "little" gears...they are Twin Disc and that's the best gear you can but in a boat, in my humble opinion. The boat I'm building now will have TD gear.

Scot

JP...

Mis-spoke, the gear in my boat is the "5010A"

Scot

I use 502s behind 300s and 210s 6bt's. I think they are a little light for your 330s. We have used the set behind the 300s hard for 4 years, and are currently rebuilding one because the captain ran it without oil after a direct guage broke and the oil ran out of the gear. Other than this the gears have been great, but I believe they are considered to be at their upper end behind the 300s.

I believe the 502s are really tough, but ZF220s might be a better choice.

Brian

JP, I have 502's in my 35' with 300hp 3116's and have never had a problem. From what I hear ,the warning with a twin disk is that if it doesn't go into gear hard then you are starting to develop have a problem. I have 1,300 hours on my engines and gears without any problems.

TD book says 320 HP with a 1.54:1 ratio
300HP for the 2:1 or 2.47:1 ratios

The 502 has had as good a reputation as any marine gear made, although it is an older design. Not sure about high power installations, though. The 5011A and 5010 that replaced it haven't fared as well. The 5011A was made in Begium, I had a pair in the 1.45:1 ratio, one went out in the slip with about 10 hours on it. Twin Disc does not have a good warranty program, I had hel, getting them to replace it. A friend had a new 5010 behind a 210 Cummins that went to pieces just like mine, TD rebuilt it at his expense, it wnet out again, and he had a local mechanic do it the next time, didn't bother wiht TD. I now have 5011A's in 1.91:1 ratio, and feel very confident about them, no problems at all. I'm pushing about 275 hp, running 22 x 24 3 blade props with no problems.

Och Mike...
That the first TD nightmare story I have heard. My 5010A has about 1,000 hours on it. I've heard plenty of Borg Warner stories. Not much either way on the ZF's.

My current project is scheduled for the 5050A, in a 1.1:1...what do you hear about this gear? I could use the 5060A, but cost is higher and weights about 70lbs more. Charts show the 5050 is more than adequate for my application.

If 5010 & 5011 have not fared well, why do you feel better with your current 5011s? Is it the ratio?

Scot

Been using TD 502's , 2-1 with my 250 Volvos for a long time. 1432 hrs now. They are very reliable but as said 300HP w/2-1 gears is tops. Thanks for the warning about the 5011A's . Dave K

Scott, it was actually a 5050 that my buddy had come apart with the 210's. Should have been more than enough gear for those engines in a 31. My original 5011A's had a lot of problems, some maybe my fault. Busted a couple of oil lines, had a leak at the lower drain that was hard to find. The one that came apart did just that. The shop that tore it down said it looked like a factory assembly problem, but TD was refusing to warrant it. Their "normal" position is they bill you for fixing the gear, then investigate. If it turns out to be their fault, them they will consider reimbursing you. I threatened to sue, they said they employ lawyers. I finally threatended to put nasty things about them in print - things that would be true, and they agreed - after an all day meeting - to give me a new gear. The manager and shop foreman of the place I took it to in Houston both shook my hand and congradulated me for pushing TD so hard. They said it is tough on them to handle a product when the manufacturer won't stand behind it. The new one did OK, but I never felt comfortable. With the weight of my boat and the gear ratio, performance wasn't what I wanted. I made a swap with another steward who had the 1.91:1 5011a's and needed less gear (ran more horses than me). I have had nothing but good luck with the "2:1's". Never had to add oil between changes, no noises, positive shifting - they have been great.

Mike the 5050 is really big gear for a 6B Cummins at 300 or 330 hp, TD factory rating is 399hp on the 5050, similar to ZF's 220....the next one, 5061 is rated at 465hp! I'm going with 320-330 in the current project. I hate to hear about a "problem" 5050 gear. Bothers me a bit. Have you read, or heard of other 5050 problems?

Do the 2.1's suffer less as a general rule than 1.1 or 1.5's?

Scot

Scot, at the time he bought the engines they could not locate a smaller gear in a timely manner, so they gave him the 5050's. I haven't heard of any more problems with them, although I do have a charter buddy who wears out Borg Warner's on a regular basis. Of the gears I have now (5011A still), one of them did the same thing new as my original one did, but I think it got warrantied easier (rebuilt, I think) - maybe because of my trail breaking. It's been great since I got it.

My gut feeling is the 1.91:1 is stronger than the 1.45:1, just from the way they feel. They certainly work better in my application, allowing me to run much bigger props to carry the load.