The OMC Cross Flow Thread

Anyone who would value that motor for what it is, will not deduct value for intelligent maintenance and bolt on upgrades. My brother boight a 70 camaro lt1/4spd rs in the early 80’s. Already the desirable muscle car models were rising in price and originality was crucial for buyers. Trouble was that engine came with a points distributor and was a pain especially when not driven much. After much toiling he swapped to hei electronic ign and packed the original points distributor up for the time of sale which came ten years later. The buyer was a collector and simply took the box and left the hei on there. Smart bolt on stuff is in no way the wrong thing to do.

now a museum piece? Fine, everything oem original. But if your going to run and use it do the smart mods as suggested. Cant go wrong with all new ignition considering the age if funds allow its a safe move. Box up the oem stuff. All good

Usually when the power pack and stator/base get out of sync its much worse because then its pre-ignition. There is a diff between pre-ignition and detonation. Detonation is when the fuel charge explodes from too much heat instead of burning. Pre-ignition is a physical igniting of the charge very early due to a timing mishap in the ignition, then the early ignition event breaks parts physically and may or may not cause more detonation. In the previous pics I posted about the diverter, that cyl then detonated from too much heat, higher octane gas like race gas may have prevented that (but that was street gas).

Here's a pic of a V8 piston/rod that experienced serious pre-ignition from the stock OMC power packs loosing track of where the motor was. The block was nearly sawn in half and was unusable afterward. It was a pristine motor too! Parts from my personal hall of "fame and shame" :D. This guy went with a full upgrade to a VSFI EFI ECU system. Pricey but no worries. The factory packs take an analog A/C signal from the stator base and using Triacs (two opposing SCRs) try to switch the packs on/off. Problem is if the signal becomes weak the trigger may or may not happen. Then bad things start to happen.

Attachment 513250

In the least if you stick with OMC stuff, pull all those connectors apart and hit the terminals with T9 spray. Its aviation grade electrical contact spray made by Boeing. Good stuff! Second cheapest is to use the CDI stuff. Better components but same lousy design.

-BL

Another problem with old NOS OEM electrical components is that they suffer from age. They use electrolytic capacitors and they are very sensitive to age and since the power pack uses a TTL style design (no cmos cpu, mcu etc. for control, all old school solid state switching) those capacitors are used in the gate level voltage levels to switch the SCRs on/off at the right time (yes I am an electrical engineer :rolleyes:) When they go, the pack no longer works as it was designed from the factory. This is why some work and some do not, its hard to predict how the parts age. Why in the least switch to CDI stuff where the components are new.

-BL

Ok guys, well you’re convincing me because I know what things like lugging and preignition and detonation can do. So it makes sense. Because I won’t be able to work on this 2.6XP realistically for a couple years, money and space, but now you have me worried about my awesome and nearly as clean daily driver: 1985 Four Winns 190 Horizon with 175 Evinrude crossflow. I did have to pull the heads on it due to an unfortunate minor overheat, but all is good and runs 50mph at 5800 rpm. I know it’s not a racer, but if the water is smooth I’ll burn up as much of the 28 gallons as I can trimmed out trying to vaporize water. Nothing more fun. So even replacing his packs with CDI isn’t great? I really don’t have extra money since I’m building a garage to work on my boats and COVID doubled the cost of everything! But I also don’t want to blow my engine. It’s also a beautiful engine, I put a couple grand into a new timer base, head and water cover gaskets, powerhead to midsection gasket, all new hoses, water sep fuel filter, carb rebuilds, replaced those little brass orifices and network of small rubber hoses, etc. of course water pump, gear lube…and I really wanna put power steering on it.

Quote:

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Originally Posted by BLisBack!

Usually when the power pack and stator/base get out of sync its much worse because then its pre-ignition. There is a diff between pre-ignition and detonation. Detonation is when the fuel charge explodes from too much heat instead of burning. Pre-ignition is a physical igniting of the charge very early due to a timing mishap in the ignition, then the early ignition event breaks parts physically and may or may not cause more detonation. In the previous pics I posted about the diverter, that cyl then detonated from too much heat, higher octane gas like race gas may have prevented that (but that was street gas).

Here's a pic of a V8 piston/rod that experienced serious pre-ignition from the stock OMC power packs loosing track of where the motor was. The block was nearly sawn in half and was unusable afterward. It was a pristine motor too! Parts from my personal hall of "fame and shame" :D. This guy went with a full upgrade to a VSFI EFI ECU system. Pricey but no worries. The factory packs take an analog A/C signal from the stator base and using Triacs (two opposing SCRs) try to switch the packs on/off. Problem is if the signal becomes weak the trigger may or may not happen. Then bad things start to happen.

Attachment 513250

In the least if you stick with OMC stuff, pull all those connectors apart and hit the terminals with T9 spray. Its aviation grade electrical contact spray made by Boeing. Good stuff! Second cheapest is to use the CDI stuff. Better components but same lousy design.

-BL

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I have regular contact cleaner…where do you get your Boeing T9 spray?

Quote:

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Originally Posted by sootypipe

Barry, are you looking at the Evinrude/BRP parts catalog on the internet or something better? You have cool
old paper parts catalogs?! 😬

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I look online most of the time but I have paper for everything I own. I don't have one for 1984. The online are useable but deficient with many of the descriptions being truncated or just wrong text. I have noticed this in particular about jets but I expect there are other issues from when this was all digitized.

If you look for an original pack, the 582138 are common with the same years OMC three cylinders.

Hit the connectors with T9 (sold in a lot of places, google it), keep the timing down, 24-26, replace the diverters, always run 91-93 street gas, synthetic oil or blend and hope for the best. Don't get too emotionally attached to these things IMO. Remember, you're 3 generations of motors behind, when you upgrade to an eTec you'll ask yourself what took so long. :D

-BL

Quote:

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Originally Posted by BLisBack!

Another problem with old NOS OEM electrical components is that they suffer from age. They use electrolytic capacitors and they are very sensitive to age and since the power pack uses a TTL style design (no cmos cpu, mcu etc. for control, all old school solid state switching) those capacitors are used in the gate level voltage levels to switch the SCRs on/off at the right time (yes I am an electrical engineer :rolleyes:) When they go, the pack no longer works as it was designed from the factory. This is why some work and some do not, its hard to predict how the parts age. Why in the least switch to CDI stuff where the components are new.

-BL

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This is exactly why I’m asking lots of questions and I’m not surprised you’re an EE, you understand a lot more than I do! I’m an ME lol. I don’t understand the electrical that you do but I love it and am listening. I am willing to do what is right for these engines. You can’t even find clean ones around here in freshwater Michigan territory. They’re all gone or beat up having had 3+ owners who did the least amount of maintenance let along actually LIKED the engine. Wanna know how crazy I am? My neighbor before I moved liked my 4 Winns he kept offering me more for it…his last offer was $20k. But you just can’t find boats and engines like these. I’ll never find another. And a new 19 ft outboard costs 3x that. I would regret selling and of course I didn’t. Some things you enjoy you just can’t replace. That’s how much I love these engines!
Attachment 513253

Quote:

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Originally Posted by BLisBack!

Hit the connectors with T9 (sold in a lot of places, google it), keep the timing down, 24-26, replace the diverters, always run 91-93 street gas, synthetic oil or blend and hope for the best. Don't get too emotionally attached to these things IMO. Remember, you're 3 generations of motors behind, when you upgrade to an eTec you'll ask yourself what took so long. :D

-BL

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Now you’re talkin’! Haha. I hate BRP for being quitters. Their poor market share was their own fault I think. I eyed the G2s always and I think one day I’ll have one! They look and sound awesome. Be a long time til I have that kind of money!

The old Fichts convert real easy to eTec, basically the same motor just a diff front half and they are all over the place and can be picked up cheap bc most are blown or simply unwanted bc of their bad reputation.

One other thing to watch on those old Xflows, the thermostats, keep them clean and replace every now and then. I don't run them at all since I'm in saltwater.

-BL

I thought T9 was an anti corrosion spray for external protection. Leaves a waxy film. Am I miss-remembering again or is there a contact cleaner version?

I use CRC QD Electronic Cleaner from the parts store.

It can be used for a lot of things. Probably a few knock offs out there too. Just simple room temp oxidation can cause problems in electrical contacts unless they're gold.

-BL

Quote:

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Originally Posted by BLisBack!

It can be used for a lot of things. Probably a few knock offs out there too. Just simple room temp oxidation can cause problems in electrical contacts unless they're gold.

-BL

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I looked up the T9 stuff as well and it seemed like an excellent penetrating oil and anti-corrosion coating that left a waxy residue but it didn’t seem to clean contacts. It would seem like I’d want to use a traditional highly evaporative solvent like contact cleaner first to clean the connectors first, then use that stuff?

Quote:

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Originally Posted by sootypipe

I looked up the T9 stuff as well and it seemed like an excellent penetrating oil and anti-corrosion coating that left a waxy residue but it didn’t seem to clean contacts. It would seem like I’d want to use a traditional highly evaporative solvent like contact cleaner first to clean the connectors first, then use that stuff?

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Yeah I’m sure that would work as well. The OMC Amphenol connectors (rubber round connectors) have a tendency to allow water in through the back of the connector where the wires enter. The waxy residue of the T9 helps seal that when you spray the entire outside of the connector. The OEMs don’t use those anymore except for 1 or 2 wire connectors. They use TE, Molex or Delphi now mostly.

-BL

Sootypipe:

In an earlier post, you asked Barry Strawn about part number information (e.g., parts manual or Internet website)…I got an OEM parts manual for my 1984 235 from eBay. It has been very helpful. The manuals are fairly small so not expensive. I think I paid $10 for mine. Search eBay and you’ll find one. If you can’t, let me know and I’ll copy mine for you.