my afterthought

[John (Taylor) Gabrowski]

Sam LeBanco:

Thank you for your insight. The only reason I will disassemble and re-assemble this factory replacement block is to deal with porting work for other anomolys that may not mean anything to a stock engine but to racing one does and re-assemble it with its new OMC pistons. For the Future I will sure watch for the wear limits you are describing to later act on. Why spend a whole extra wack of extra money for other aftermarket pistons where you have a new set to count on from the original purchase price to work with first time around at least.

Any advice on breaking the rings in while on petroleum based oils and when switched over to synthetic and advise what synthetic is best for these 3 Holers overall.

Again thanks.

[Sam La Banco]

John
Everyones got there own ideas about break in also as you know, I've tried many ways but went back to a much slower and longer period than I've used in the past.

The reason for the switch was my research on a common problem with these engines; microwelding. Which as you probably know is the transfer of aluminum from the ring groves to the the bottom side of the rings, (mostly the upper one). When this happens they do not seal well.

This engines rings have a very large cross section which makes them very heavy (great rings for fishing and sking). To heavy for the RPM range we use them in. If you have a copy of Gorden Jennings book "the 2-stroke tunners handbook" he explains in great detail the subject.
Using the equations he presents to help predict the problem of "ring flutter"
you will find that these rings are in danger of flutter as they get over 7800
RPM.

We have always known this, and figured that was why we generaly find evidence of the problem during rebuilds somtimes, as we are turning a bit higher.
After seeing more microwelding than usual, during last years tear downs I decided to research this subject. There is to much information to type, but lets just say all modern 2&4 stroke engines have coated rings. Most of the coatings are propritery and I could not find a source to do mine.
There's a lot of coatings out there but not these.

After not finding a source I was frustrated and called and old engineer friend
I worked with at OMC, Dave Haman (we did the design work on the 45ss engines midsection and gear cases, also the OMC "A" motor.)

By the way he is currently the manager of Bombardier's (OMC's old) test station in Florida, between that and all his time in engineering in Waukagen,
he's a pretty smart 2-stroke guy. As we discussed the problem, he filled me in on something unknown to me, that being, microwelding most happens during a tough brake-in,... then just gets worse.

Well, now I break the engines in like my old stock outboard days, nice and slow.

As far as oil goes, man, what a can of worms no matter what I would say, there are a million other idea's out there, so I will tell you what we have used in this engine with good results, Bombardier, Yamaha R and Xamax.

[mxp864]

I have alot to learn.

[John (Taylor) Gabrowski]

Sam LeBanco:

My aircraft pilot neighbour who go me involved in all this in the mid 1960s when doing his rebuilds on his C-Racing, C-Service and then his racing KG9 Merc would spray all his rings with some kind of graphite spray on each side that would dry and harden before he would flip them to do the other sides for installation. This he claimed would help with a slowing of the break in of those real wide rings he used. He also used some kind of graphite additive in his fuel mixes as well that left a grey residue streaming down outside his exhaust ports. He never talked about things such as ring flutter and if he did I was too young to understand that, he kept me to basics as a protege. One thing he did mention was wanting some kinds of rings that fitted ring groves as standard but tapered outward to half the ring grove width at the cylinder wall as being a better racing ring. That was still greek to me too! I never saw rings like that until the later 1990s for Mercs running Turner pistons. Just last year I made up a D-Mod gas engine with NOS Turner ultralight 2 ring gasser pistons where I installed these type of NOS tapered to the outside half width rings that looked they were a kind of chrome high tension ring material. I have yet to test the engine. I take it that narrower rings of suitable material took out ring flutter at these higher rpms? I suppose that these modern day teflon and ceramic coatings and sprays also help prevent ring problems at high rpms?

Its entirely new to me about metal transfers from one side of the rings groves to another. I saw some weird stuff on the Turner piston ring groves on scortched, scored, melted and fried pistons from Alky deflector engines but never on the stock or mod Mercs I have worked on. Is that what you mean by metal transferance? I would not have recognized what I was seeing other than thinking that the piston maker made things that way?

There is so much to think about in your post I have to go into Jennings material to get further out of what your saying. For anyone else to read I do believe there is a thread on BRF with links to download his, Jenning's book.

Thanks for the break in proceedure advice, slower means better or even more long lasting parts wise hopefully. I notice you did not mention Red Line synthetic 2 stroke oil for gasoline fuels. With sitting on about 6 gallons of it, I must ask if it has fallen out of favor these days??

A few years ago I had the misfortune about not knowing anything about Amsoil and that Amsoil synthetic was just that being synthetic and could not figure out why the Merc 55H just would not break in its rings no matter what I did. When I found out the whole experience soured on me thinking it was a weird engine of no use and there it was the synthetic oil screwing up the rings breaking in all along. What a horrible lesson to learn about not knowing oil brands and using them thinking in that case thinking Amsoil was petroleum based with no can or specs to read and find out any different at the time.

I am defintely going to use the new OMC pistons already loaded into the replacement complete block and be mindful of all your pointers.

Thanks for all that info.

[Sam La Banco]

John, sure wish I could get some of that stuff your friend used on his rings.

Actually there is some stuff like that avaiable from Dow Cornning and a few other places, that guy was pretty smart. I would not use it in the fuel though.

Not all engines suffer from Micro wellding, I never saw it on any of my stock or modified engines.

The best way to describe microwelding is, you will know it's happenning when you find small pin head or smaller size deposits you can feel on the bottom side of the rings, when you clean the ring up, the spots will be the same color as aluminum (because it is). You will see the associated pock marks on the ring glands. To much heat.

I have never run red line, but my best friend builds many many kart engines
at his shop, and they use it when they can't get the Xamax I listed.

The rings in the sst60 motor (56 cuber) run pretty hot, but not as warm in the 49 cuber. The 49 cubic "sport E motor was a way way better engine, with a much more robust block and quite a bit more water jacketing.(great motor)

When testing projects while I was at OMC, from time to time Jimbo would also be out testing at our test station that was in fox lake Ill. so of course we would stop to watch. Once while testing his Mod 50 motor, I heard Jim Nerstrom tell Jimbo to keep the motor under 9000, I'm sure he didn't always do that though. I think the mod 50 rings were similar but not sure.
I don't think they had problems with microwelding but that block had a lot more cooling then out "60" motor also.

[John (Taylor) Gabrowski]

Sam LeBanco:

The graphite spray that Ted Coates used on the piston rings was different and he got it from mechanics at his commercial airport repair depot. The small can of graphite lube mix that was sold for fuel mixes specifically and different from the rings sprays was from "Wynnes" products, who also made a lot of other specialty lubricants to general sale to the public as well. He told me it was good for the OMC bushings still in the engine as well. He was also in the midst of converting his engines to more modern bearings and seals. After conversion he kept on using the Wynnes graphite lube in his fuel.

I thought the sparkplugs would foul on graphite being what it is but he always changed sparkplugs on the Elto and Johnson every heat anyway with clean ones so he never saw a problem by using his practices of changing plugs religiously to get excellent starting and running. For some reason he only changed sparkplugs on the Merc KG9 (Champion J4J) on the next race date but not at any other times between heats or even on a 2 day race weekend. He had no problems there either.

I was under the impression that the OMC 3 Holers being loop charged that they would run inherently cooler than their older deflector engines by virtue of the new technology but I am being informed that in either case that is just not so, be it a 35HP deflector or a 3 Holer looper. That for a ski/fishing based market that they are oversquare engines with way larger piston bores than crankshaft stroke making them high revers by their nature. Is there no way to make them transfer heat faster and tuned to run cooler? When it came to Merc/Mariner 3 Holer direct charged engines I thought my burn them to bits days were over and OMC a lot lot better?

People I know that are working on OMC 35 - 2 cylinder class C Modifieds are going to be very interested in your posts as there are 3 versions ports wise of these deflectors being constructed during their same years of production that from examining their innards as they put it have "racing written all over them"! They seriously want to boot some Yamato butt and are concerned about anything that can be done to make these engines heat managed, powerful and reliable given engines spec'd limitations for the class?

The nice thing about all the OMCs of yesteryear is that they are so so plentiful and so inexpensive to buy used albiet that they are all so heavy mainly from flywheel weight. Do these OMCs have to have such heavy flywheel systems to keep the whole motor stable or can they be made way smaller and lighter and still keep stock ignition parts going?

Sounds like asking for a lot of advice, yes but there are a lot out there who want to race and see racing spread through economies of scale, so OMC it is and just like Mercs here everything from the similar eras are so inexpensive for our sports use.

[Powerabout]

Looks like people are hard anodizing the piston crown and ring grooves to get over the microwelding problems these days

[JohnsonM50]

Sam LeBanco:

The graphite spray that Ted Coates used on the piston rings was different and he got it from mechanics at his commercial airport repair depot. The small can of graphite lube mix that was sold for fuel mixes specifically and different from the rings sprays was from "Wynnes" products, who also made a lot of other specialty lubricants to general sale to the public as well. He told me it was good for the OMC bushings still in the engine as well. He was also in the midst of converting his engines to more modern bearings and seals. After conversion he kept on using the Wynnes graphite lube in his fuel.

I thought the sparkplugs would foul on graphite being what it is but he always changed sparkplugs on the Elto and Johnson every heat anyway with clean ones so he never saw a problem by using his practices of changing plugs religiously to get excellent starting and running. For some reason he only changed sparkplugs on the Merc KG9 (Champion J4J) on the next race date but not at any other times between heats or even on a 2 day race weekend. He had no problems there either.

I was under the impression that the OMC 3 Holers being loop charged that they would run inherently cooler than their older deflector engines by virtue of the new technology but I am being informed that in either case that is just not so, be it a 35HP deflector or a 3 Holer looper. That for a ski/fishing based market that they are oversquare engines with way larger piston bores than crankshaft stroke making them high revers by their nature. Is there no way to make them transfer heat faster and tuned to run cooler? When it came to Merc/Mariner 3 Holer direct charged engines I thought my burn them to bits days were over and OMC a lot lot better?

People I know that are working on OMC 35 - 2 cylinder class C Modifieds are going to be very interested in your posts as there are 3 versions ports wise of these deflectors being constructed during their same years of production that from examining their innards as they put it have "racing written all over them"! They seriously want to boot some Yamato butt and are concerned about anything that can be done to make these engines heat managed, powerful and reliable given engines spec'd limitations for the class?

The nice thing about all the OMCs of yesteryear is that they are so so plentiful and so inexpensive to buy used albiet that they are all so heavy mainly from flywheel weight. Do these OMCs have to have such heavy flywheel systems to keep the whole motor stable or can they be made way smaller and lighter and still keep stock ignition parts going?

Sounds like asking for a lot of advice, yes but there are a lot out there who want to race and see racing spread through economies of scale, so OMC it is and just like Mercs here everything from the similar eras are so inexpensive for our sports use.

One question is how fast are the C-mods now? There's no question about power out of a corner. Ive been modifying 25/35OMC's for fun which also means no rules except they have to be closed exhaust to run locally. The flywheel is heavy, why is probably the go slow aspect of motoring that they are good at. The steel starter ring can be easily removed but its not recommended to cut down the aluminum. The inner dia is relatively small so a custom or retrofitted wheel is possible ?. Also the balance work on these is probably not meant for more than the 5000-5500 R's intended. The piston assembly weights are likely to not match up very well either. There are a good number of different versions of the cross flow twin or parts contained, while mostly looking the same externally. I'm not near enough to where they are being raced [not allowed in the APBA]. I do think there is potential to be competitive with the 302's or MK30H mods in time as more experts take interest.

[Tim Kurcz]

what would be a better block then, a sst60 or to get a 90 hp yammi?

Lemme see, the SST60 is 56 cubic inches, the Yamaha 90 is 70 cubic inches. Which one looks like a better candidate?

Tim

[Tim Kurcz]

Sam Lebanco: Two summers ago at a neighborhood garage sale I picked up a brand new NOS - OMC 49 inch 3 holer complete block from the factory along with the blown up fishing motor it was to replace where its block had kicked a rod through the side of the block for $200.00 bux. I bought it specifically for a Super E Modified engine. Talking to other people, reading the posts here and elsewhere leaves me confused as there are so many pros and cons from everyone to using the OMC pistons or aftermarket pistons like Wiseco. Reading your post just adds to wanting to do the right thing and I have no experience with these OMC 3 Holers. Will you advise as your experience base is profound?

Hey John,

Just finished with my 666 and have time to answer. Be wary of NOS cast 49.9 pistons they are known to fatigue, crack, and blow chunks. When you disassemble your perforated powerhead you'll more than likely find the rod and crank perfectly intact, and the window caused by piston chunks getting trapped between the rod and crankcase (sometimes block). I've seen dozens like this, and most are easily repaired by heliarc and a little grinding. Though casual observers think the rod has thrown, but I've never seen a broken OMC triple rod unless run without oil (got one in stock), and have never, ever seen a broken crank.

If you purchase late production cast pistons and judiciously deburr and smooth, they will last years in a fishing engine. If you intend to race the engine, be sure to dye penetrant check cast pistons before they go in and NEVER install used cast pistons unless you know their history. I've used both OEM and Wiseco forged aftermarket pistons in racing triples with good results. In these cases, we change them every three seasons regardless.

Sam's advice is superb given his SST60 racing experience, in particular the ring flutter, micro-welding as pertains to breakin. The one item I don't recall being talked about is proper engine warmup. Most racers start a stone cold engine at full throttle to get on plane immediately to mill the course. Short of flying immersion, I'm convinced this is the single most damaging event a race motor experiences. Consider that cast pistons expand less and run tighter clearances than forged (as Sam pointed out), so they are less prone to cold start damage. Forged pistons do expand more and don't take well to WOT starts. They need be warmed gently - actually it's best to warm any engine gently - before stabbing the throttle.

Just my two bits,,,,,,,

Tim