The OMC Cross Flow Thread

[sootypipe]

[QUOTE=BLisBack!;3370908]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.

Good point, I can see water getting in from the back side where the wires enter. Those connectors seem to be really crude/old style connectors compared to what is used today. I should clean and spray everything on my 1985 175 horse engine even though it’s super clean and running well. I should also replace the old CD packs with new ones from CDI it sounds like. If I’m keeping this engine stock, you think 5800 rpm is good or should I prop it even faster? I have timing set to factory and jets are what came in the carbs when new. I just rebuilt the carbs.

[sootypipe]

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.

Thanks a lot for the offer! I just noticed that in the back of the owners manual for the 2.6 XP they basically put a parts book so I actually have one! I just need to look at EBay for one for my 1985 175hp V6…

[BLisBack!]

The last time I had a stock 2.6 crossflow on the dyno it made 215-220hp at the prop and the torque peak was around 3500-3800rpm. So at 5800 you're way over the peak and unless your setup needs more rpm, or you're looking for more top end and the boat can take it by getting the motor out of the water, I'd leave it IMO. That said, and I'm sure others on this thread will agree, those motors will spin 5-6k easily all the day long if you need it to.

-BL

[sootypipe]

I'm just asking because I know 2 strokes in general don't like lugging. For instance, most Merc inline 6's were originally rated at 4800-5300 RPM, but the guys who know those really well generally seem to recommend running them 5500-6500 RPM. One experienced OMC mechanic turned dealer owner said to run my 175 horse crossflow 5600-5800 RPM, 6200 max. I'm not necessarily looking for the most power but what's best for the health of the engine, to avoid detonation and pre-ignition and maximize the engine life. I want to increase the jet sizes in this one first since it's my daily driver.

The last time I had a stock 2.6 crossflow on the dyno it made 215-220hp at the prop and the torque peak was around 3500-3800rpm. So at 5800 you're way over the peak and unless your setup needs more rpm, or you're looking for more top end and the boat can take it by getting the motor out of the water, I'd leave it IMO. That said, and I'm sure others on this thread will agree, those motors will spin 5-6k easily all the day long if you need it to.

-BL

[sootypipe]

Hi guys. So you probably know I have a 1985 175 hp Evinrude and a newly-acquired 1984 Evinrude 2.6 XP. Based on your advice, I want to get some sets of bigger main jets. So I am going to ask you guys here if you have any new ones or used ones you know are good you are willing to sell. I see some are on Ebay here and there for anywhere from ~$8-20 per jet. Going to cost a lot to play with jets huh! Well, with the help of my manual and parts books, this is what I'd be looking for to fatten up both my engines, priority being the 175 since I use that one now and the 2.6 will be a project boat when I get a garage built:

175:
OMC p/n size
320661 61C
317607 62C
321559 63C

2.6:
OMC p/n size
328554 66C
317183 67C
328555 68C

I'll also ask this question as a new post on this forum so others maybe see it.

[john j 80 viking]

Do you know what jets are in your motors at present?

[BLisBack!]

You pay for the shipping I'll send you all my jets and carbs free. Merry Christmas. Once you go EFI you'll never go back

I ran 67C (maybe 69 on 3&4) for all out power and short runs but ran 69C straight up on all 6 for longevity.

-BL

[sootypipe]

Both should be stock, both boats/engines came from original owners and super clean (although I haven't looked at the jets). According to the original parts books that would be:

175hp:
321499 60C (.060)

2.6 XP:
322810 65C (.065)

Do you know what jets are in your motors at present?

[sootypipe]

Awesome, sending you a PM now!

You pay for the shipping I'll send you all my jets and carbs free. Merry Christmas. Once you go EFI you'll never go back

I ran 67C (maybe 69 on 3&4) for all out power and short runs but ran 69C straight up on all 6 for longevity.

-BL

[BLisBack!]

65 on the mains!?! Thats way too low IMO. Maybe those are the 4 stage carbs? Where they have the high speed enrichment circuit high up in the carb throat? That would make sense then. I'll see if I can dig one up and post a pic.

Usually I just ran the 3 stage carbs. I saw the motor has the good tight heads too so its gonna have more than average compression so you'll want to get this right.

-BL

[BLisBack!]

4 stage carb, notice the jet in between the venturis with the outlet to each venturi, these carbs had 63Cs in them, very low bc of the high speed enrichment circuit most likely. Don't know what they're off of, they are the big ones 1-3/8" though. Maybe some of the OMC history experts on this thread know;



You can see the feed tube go through the middle of the float into the bowl;


Here is a standard 3 stage 1-3/8" off an '89 175 GT;



-BL

[James45157]

The omc manual for the 2.6 xp or gt model 265 hp at 6250 rpm the guys that ran them local turned them way past that 6600 to 68oo plus the ones that the guys ran had different lower unit from factory

[sootypipe]

No idea there were so many differences. I see that there’s a 1 3/8 cast into the inlet face, cool! I need to see what’s on my engines, particularly the 175 horse since I use it now and need to be sure I take care of it. The 2.6 won’t run for a while. Honestly not sure what you mean by 3 stage carbs, I don’t really understand how they work other than the basic float bowl and Venturi principle, but not sure what’s what in these. My only experience so far was rebuilding the 3 on my 175 by the book a few years ago.

4 stage carb, notice the jet in between the venturis with the outlet to each venturi, these carbs had 63Cs in them, very low bc of the high speed enrichment circuit most likely. Don't know what they're off of, they are the big ones 1-3/8" though. Maybe some of the OMC history experts on this thread know;



You can see the feed tube go through the middle of the float into the bowl;


Here is a standard 3 stage 1-3/8" off an '89 175 GT;



-BL

[BLisBack!]

3 stage meaning 3 fuel circuits. Idle, part throttle (or mid) and the main circuit (fed by the main jets). The 4 stage have an additional circuit that comes in after the mains, the high speed circuit.

Daniel Bernoulli was a genius

-BL

[john j 80 viking]

If your carbs are tuned properly, the separate stages overlap and aren't at all noticeable. The idle and midrange stages are controlled by the butterfly uncovering tiny holes on the engine side of the butterfly. The amount of fuel the first 2 stages meter is regulated by the air jets that are located on the airbox side of the butterfly. Now that I mentioned the airbox, it is worth mentioning that V6 crossflows almost always run better with the airbox on. The only modification I made to it was holesawing 6 1 1/2" holes on the sides of the cover opposite of each other.