articfriends

iTrader: (1)

I worked as a high pressure cryogenic plant operator my last 2 years in the Navy,I'm not convinced it does anything whatsoever. We dipped ALOT of different things in liquid nitrogen when we were bored (like wrenches,sockets,chunks of steel etc). When you dip something the stuff really boils until the object being dipped reaches the same temp as the nitrogen (-322 degrees fareinheit) then it quits boiling. We tried doing that to pieces of steel then filing,grinding and bending it,never made the slightest difference. Maybe they are heating it up to cherry red then dipping it while its hot which we never did. We tried treating our sockets in it,they still wore exactly the same. The object would shrink a few thousandths,the same amount it would expand if heated to 322 above fareinheit. We tried freezing stuff in it then breaking it (we were bored),nothing ever really shattered while it was froze other than frogs and mice (things with moisture in them),Smitty

articfriends

iTrader: (1)

The gears from what I could find are made from 8620 steel,the heat treater used a schedule and process for that grade steel. The rockwell test he did before heat treating them/hardening them deeper wasn't on the gear teeth,it was on the body of the gear as the whole gear is case hardened equally around the entire piece.When I took my spare drive apart the gears were chipped exactly the same as the ones pictured but only 1/3 as bad. When I have had people look at them that know more than me there consensus is there is obviously surface contact where the extreme pressure has forced the oil from between the 2 surfaces allowing the metal to contact and wear thru the hardened outer surface. I have never had a problem with the gears spitting or shearing a tooth right off,just the surface flaking away until the softer metal underneath starts to errode quickly. Your opinion or knowlege and any help is greatly appreciated as I only know basic mettalurgy (like what you learn in metal shop in high school) and may be going in the wrong direction with this. PM me with a phone number or address,I'll gladly send you a set of gears to have tested or analalized. I'm trying to see if I can find a solution to my problem with lower gear life. Most of us can buy a set of new lower gears for 450$ and if we could get them heat treated for 33$ it would be better than paying a big name outdrive builder 600$-800$ for same exact gears plus ten times as much for them to heat treat them in the same fashion.When I talked to Aaron at max machine worx their R&D consited of them doing basically the same thing I'm doing then selling them or installing them in a few local havasou boats and having guys run them to see what happens,I can do that myself . They did tell me they are working on building gears from scratch also from some exotic 9310 alloy with a different tooth pattern and count thats close to the stock ratios that will fit our merc and imco housings,that sounds the most promising yet. Thanks for any input you and anyone else can give or help with,Smitty

articfriends

iTrader: (1)

I read the link to cryo treating you posted RLW,we never did it for 36 hours,only a hour at the most plus we never did it in a controlled enviroment where we lowered the temp in 1 1/2 degree increments every minute,maybe there is some merit to it and I prematurely condemed it from my crude attempts at it,Smitty

Ratickle

I'm really surprised they are 8620. On 8620 (the last two digits denoting the carbon content, 20 allowing a range from .15% to .25%), getting them extremely hard would cause brittleness. I have a friend who worked on the propellor development metallurgy for Mercury. I will print out all of this post and have him review the processes and see if he can use any of his contacts to find out more from Merc. Also 9310 would have less carbon than 8620 and therefore be unable to achieve the same Rockwell hardness as 8620. I've never had a requirement for 9310 but will find out it's properties and recommended usages. You may not need to send the gears, I'm sure I can find some broken one's over here. I will persue this because now I am very interested in the metallurgy and reasoning behind it. It's kind of like props, everyone thinks they are 316, but 15-5 or 17-4 is what most are made out of.

Big Block Billy

How about also having gears x-rayed and or magnafluxed or zyglowed.
Bam has a treatment for gears. They coat alot of Trs stuff.
Sure Bravo's can be made better, but the real answer is a bigger drive with bigger internal parts. The rear axle of the smallest cars has more beefy internal parts than any outdrive, and the car's not working hard, and not trying to process 950 HP.
Do a Konrad conversion , and you will be able to use the boat more and work on it less. It really is an awesome drive setup. My friend went for it on his 38 kv Scarab, and no longer has to worry about blowing up drives ! That was with 720 HP. BBB

Ratickle

BBB, What was it you are working on now?

Mr Gadgets

Ratickle,
I have plenty of gears that could be tested.. Your welcome to them.. I am very much interested in any results also..

Thanks
Dick

articfriends

iTrader: (1)

BBB,I could have gears x-rayed or magged but I have NEVER spit or broke a tooth off or fractured one. The lower gears just slowly wear thru the hardened surface and start to errode and get louder and rougher putting fine metal thru out drive.If I jumped on the throttle and the gears just blew apart or split in half it would be important to me but not the case with mine. I'm approaching 200 hours on my upper gears and parts,130 hours with 725-750 hp and 60 hours with 940 plus hp,these lower gears failing is the last weak link,at least in my case,so if I could get them to last I would have virtually no outdrive problems. As far as converting to a konrad I was excited to hear about there bravo conversion but on top of the fact I got 20g's invested in my drive and my spare drive its out of the question for my application. My boat has a molded inner liner and moving my engine fwd 3 inches and up for the extra clearence required for the transmission is physically impossible unless I were to exstensively modify my interior as my blower pulleys are already almost touching the back seat. When my drive finally finishes off a set of lower gears 1/2 way to 2/3rds of the way thru a season I buy a set of gears for 450$ and 200$ worth of bearings and I'm back on the water plus I throw my spare drive on while I fix the drive and order parts so I don't miss any boating. I tore the spare drive down a month or two ago as a preventive measure,its been on the boat somewhere between 20 hours in past 3 years. The gears were wearing away but not as bad as the ones in the picture. If I can't make the gears last longer by heat treating them or buying some that have been professionally done I'm just going to start changing them every 40 hours as a preventive measure,it would be different if I was paying someone else to do the work and paying top dollar for the parts,Smitty

Outdrive1

Off the subject Smitty but what fuel pump are you running? I just ditched the Carter I had and put an 11108 Aeromotive in it's place. The way AZSM had it plumbed was, gas tank with 1/2 lines, Carter fuel pump, Merc seperator, fuel cooler and regulator with a return to the seperator, last to the fuel rail. I'm wondering if I should have a return somewhere on the other side of the pump or back to the tank. To tell you the truth I think the stock pump is still in there and hooked up at the fuel cooler. My biggest concern would be adding a return line to the tank, how can you do that without emtying the tank and cleaning it if you are tapping a fitting into it?

Ratickle

When I added the Haltech fuel injection to the Scorpion I had an aluminum tube built about eight inches long with two tubes inserted into it bent to direct the fuel flow towards the tank and AN fittings on the outside. Then cut the hose from the fill to the tank, removed six inches of hose, inserted the tube and connected it to two braided return lines. Make sure you also ground the new tube to the tank. Depending on tank placement, most also have an inspection cover which can be removed and modified.