The OMC Cross Flow Thread

[sootypipe]

How do you get past the 6200 rpm limiting power packs?

[LakeFever]

Xp has stiffer motor mounts. Considering the age you probably want to pin them. Didnt the xp come with higher rpm limit power packs too?

[racer]

The bad rpm range is 64 to 6600 as for the rpm limiter try to find an original set of 79 to 82 power packs as they did not have limiters in them. The older packs will need wire end changes at the coil.

[john j 80 viking]

Well, this is a 16 ft Checkmate Sportfire, only thing heavy about it is that it has 2 fuel tanks (a 19 and 21 gal).

Well let me get the thing all tuned and carbs rebuilt and ignition dialed in. Then I’ll play with props and see if I’m daring enough to get it past 6500!! Haha!

About carb jets, anyone know what size the stock ones are? Have any OMC part numbers for replacements that are larger in size? What about buying a really nice/expensive (not Amazon junk) micro drill set) to drill them out? Can you get a good enough finish?

I've seen 62's and 63's in the later fishing motors with bathtub heads. My 1981 that came with the tight heads and a factory recommend 30* of overall timing came with 64's. Factory jets I'm told we're drilled undersized then reamed to the finished size. I do know that APBA hydroplane racers think nothing of soldering closed the orifice and drilling to the desired size. Keep in mind that even the best drill bits will always make a hole that is slightly oversized, which is not a bad thing.

[Forkin' Crazy]

Depends on what carbs and the year on what jets. The last two year XP GT had the best carbs. I've used several different years, and racer told me the last two years were the best. Of course he was right!

I don't like drilling jets, but that is just me. You really need reamers to get a smooth cut and then there is the chamfer that needs to be in place.

[sootypipe]

Xp has stiffer motor mounts. Considering the age you probably want to pin them. Didnt the xp come with higher rpm limit power packs too?

How do you pin the mounts?? Abd yes the XPs and GT’s have higher speed power packs (6200). The 150/175/185/235 are 5800 if I remember correctly from looking at my manual.

[sootypipe]

I've seen 62's and 63's in the later fishing motors with bathtub heads. My 1981 that came with the tight heads and a factory recommend 30* of overall timing came with 64's. Factory jets I'm told we're drilled undersized then reamed to the finished size. I do know that APBA hydroplane racers think nothing of soldering closed the orifice and drilling to the desired size. Keep in mind that even the best drill bits will always make a hole that is slightly oversized, which is not a bad thing.

Hearing that, I probably don’t want to drill out my own jets. I like a nice starting and idling engine. Racers care only about WOT so I can see them not minding driller jets and not messing with perfection. I assume the jets are a standard type of jet you can buy many places?

[sootypipe]

Depends on what carbs and the year on what jets. The last two year XP GT had the best carbs. I've used several different years, and racer told me the last two years were the best. Of course he was right!

I don't like drilling jets, but that is just me. You really need reamers to get a smooth cut and then there is the chamfer that needs to be in place.

2.6XP’s and GTs were only made two years, 1984 and 1985, at least according to all the information I’ve found including the BRP parts lookup. Or maybe you’re talking about the 150s?? Or did they make some 2.6’s that weren’t in any of the brochures, catalogs, etc?

[Forkin' Crazy]

2.6XP’s and GTs were only made two years, 1984 and 1985, at least according to all the information I’ve found including the BRP parts lookup. Or maybe you’re talking about the 150s?? Or did they make some 2.6’s that weren’t in any of the brochures, catalogs, etc?

I have both year carbs of the XP/GT 2.6L. And they were jetted differently if I remember right. I was running both, but used the last year 2.6 carbs on my 235 and my 2.6 XP/GT and they worked the best. My last was just a new replacement XP/GTblock when I bought it. But had the CNC cut ports. The old 1980 carbs had 4 circuits instead of 3 like the newer XP/GT 2.6L carbs. Newer XP/GT 2.6 carbs brought that old 235 alive.

[sootypipe]

I have both year carbs of the XP/GT 2.6L. And they were jetted differently if I remember right. I was running both, but used the last year 2.6 carbs on my 235 and my 2.6 XP/GT and they worked the best. My last was just a new replacement XP/GTblock when I bought it. But had the CNC cut ports. The old 1980 carbs had 4 circuits instead of 3 like the newer XP/GT 2.6L carbs. Newer XP/GT 2.6 carbs brought that old 235 alive.

Interesting that even in the two years of the 2.6 XP/GT, they jetted the carbs differently!

[LakeFever]

How do you pin the mounts?? Abd yes the XPs and GT’s have higher speed power packs (6200). The 150/175/185/235 are 5800 if I remember correctly from looking at my manual.

theres a few good threads on this process. This one has pics its pretty easy

https://www.screamandfly.com/showthr...wer-mtr-mounts

[BarryStrawn]

Two different sets of carbs in 1984 and another in 1985. So three variations and all jetted differently. If I remember correctly.

I suggest checking the part numbers on the power packs to see what you have. May have been changed back in the day to older unlimited rpm or to who knows what over the years to keep it running.

And go through the carbs to see what jets it has and which carb version. They should have tags. And new jets are not available but can be found.

[sootypipe]

I’ll see what carbs and jets and power packs I have. I may need power packs or at least one and maybe some coils. I tried the boat once at it would hardly accelerate, topped out at 40 once it finally planed. May have some dead cylinders.

For jetting, does anyone have a list of carb part numbers and jet sizes? Maybe helps when buying used parts and engines.

As for setting timing to 26 deg, I think the original spec is 30, so that means you guys are recommending 26 deg before TDC, more RETARDED than the factory?? OMC had it too advanced? 30 deg would do some damage? It seems anyone that mods engine says to advance timing for better performance and lower fuel consumption.

[Instigator]

I think my 2.6 XP was an ‘83.

2.6XP’s and GTs were only made two years, 1984 and 1985, at least according to all the information I’ve found including the BRP parts lookup. Or maybe you’re talking about the 150s?? Or did they make some 2.6’s that weren’t in any of the brochures, catalogs, etc?

[racer]

I think my 2.6 XP was an ‘83.
Gary is correct the 2.6 XP built 83 to 85 and yes they had different carbs that require different jet so you need to be careful. Jets are specific to E/J and need to be a C series for those carbs as flow direction is different than the D series jets for the later engines.