Well you stated anything crossflow so v-4 mod on a 15ft pacecraft race boat 7200@ 85mph gps 26 cleaver pretty good for 4cyls and was very dependable,raced it for 3 yrs untouched built 6 off them never had one blow up just my 2 cents
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Well you stated anything crossflow so v-4 mod on a 15ft pacecraft race boat 7200@ 85mph gps 26 cleaver pretty good for 4cyls and was very dependable,raced it for 3 yrs untouched built 6 off them never had one blow up just my 2 cents
Thats very impressive!!! Which motor were you starting with (140 etc.) Thanks GaryQuote:
Originally Posted by racervboat
Ok so sorry for just budding in and don't mean to step on anyone's toes but I have a question.
Is there a certain point, when a crossflow v6 is jetted right, that you should not stay at full throttle for long distances for the chance or burning it up?
I have a 1980 hydrostream vandal with a mod 200 crossflow that 90 mph in 1000 ft at 7000 rpm with a 28 et. I have not tried a bigger prop yet but am considering it. It's not like I can stay in if for super long as it is, being such a small boat but I would like to put a crossflow on a fast family boat some day.
Thank you for any info
Scott
I know this thread is a bit old but I’m hoping some of you guys are still around. I’m an OMC V6 (and V4 fan), and am wondering where you should run a factory bone stock XP? And while I’m asking, what about a 1985 175 (also stock, crossflow, my baby, does 50 on a really nice 4Winns Horizon 190 at 5800 RPM with the original stainless 21 inch. Thanks….
These guys are still around and I’m sure will chime in. However, I think you need to be more specific about what you mean by “where you should run”? Do you mean RPM? Timing? Also, be specific about the Year model and horsepower of this “bone stock” XP and you’ll get all the answers you need from these guys. Forkin has helped me a lot in the past and he knows what he’s talking about so maybe he will opine. Good luck.
Thank you very much for your reply sir. I’m sorry for the lack of information. To add more specific details:
-Yes I’m wondering what would be the recommended RPM to run this 2.6 XP engine at. I know there’s a an originally published range but it seems most 2 stroke outboards with experience have been recommended to be run higher.
-My specific engine is an original low hour unmodified Evinrude 2.6 XP, 1984. These engines had no power rating but were based on the 235 hp engine, just guessing maybe 250?? It’s on a 1984 Checkmate Sportfire, very small, 16 ft, custom ordered package, boat rated for a max of 140hp. Original receipts and manuals.
Hope that helps!
No problem…I actually have the same motor. The OEM Service Manual says that the Full Throttle Operating Range (for 2.6 models) is 5000-6000 RPM. The manual also says that the RPM Limiter Powerpack limit (for 2.6 models) is 6200 RPM. As for the actual HP, if it’s bone stock, my guess is 235 - 240 but that’s just a guess. Others should be adding their opinions and knowledge which may conflict with the numbers I’ve posted but that’s ok…I’m citing what’s in the OEM manual but that info might be dated…
In my experience with crossflows you just wind em out until they go no higher. 6-6500ish
for a v6 you need to avoid the critcal speed zone 6400 to 6600 i think it was?Quote:
Originally Posted by LakeFever
2.6 GT XP made more power than a 235.
It's 6200 to 6300 rpms. It is believed that there was a harmonics event that would sometimes result in a broken crankshaft.Quote:
Originally Posted by powerabout
My very successful engine set up for when I was drag racing was 30* of timing and removal of the rubber bump stop only when actually racing, which will give an additional 2-3*. Relieved exhaust with a Bobs snout and the midsection cut out to match it (it's a lot of relief). Red Holly fuel pump set to 7psi. Carb floats lowered 1/8" from level with the carb body. I ran #67 jets in 75-85* weather. I forgot what I did with the air bleed jets, but I remember that it was really important for good initial throttle response and getting out of the hole. Check your carbs for full throttle and synchronization.
Stick to the stock timing or a little less for just screwing around on the lake and always run midrange to premium fuel. Never run old fuel and make sure you have a water separator. These last 2 points may be the most important. I've seen 7200-7300 rpms while prop testing, but my 24" drag props always ended up topping out the engine at 6700-6800 rpms.
I actually have a 1985 service manual that covers this engine and kinda forgot about looking in it for the speed spec, but I know experience has many times taught guys that the 2 strokes like to run faster than the originally recommended range, usually to avoid things like pre-detonation and pits in pistons etc. I want to protect this engine and get the best performance out of it without modifying it. And so you think the power isn’t much more than the 2.6L 235hp
model?
My previous reply was meant to be a reply to 97mirage, I’m still figuring out how the website and threads work!Quote:
Originally Posted by 97mirage
Thanks for all the good tips! I don’t think I’ll do any mods like you did for racing but I’m going to go through the engine timing, sync, rebuild the carbs, those little brass hose barbs (check valves or orifices), replace all hoses, etc. I already rebuilt the fuel pumps and replaces the fuelQuote:
Originally Posted by john j 80 viking
lines to the engine and those to the pumps. Actually, I plan to add a NOS OMC period correct remote mounted spin-on water separating fuel filter. I doubt I’ll see much water but those little screens on the fuel pumps wouldn’t seem to catch much. I always run no-ethanol rec fuel which here in Michigan tends to be 91 octane.
Question for you guys, I’ve always been thinking about getting an ultrasonic cleaner for doing carbs., any of you guys use one? Do you recommend this or not? And recommendations on brand and size? Can you damage these carbs using one? What fluid do you use? I saw where one guy used gasoline. What about diesel fuel? I use that in my parts washer. With stubborn stuff I use OMC Engine Tuner, special ordered a gallon and keep it in a metal gallon paint can, but it’s very harsh and may be too much for an ultrasonic. Thanks in advance. I appreciate the knowledge from you experienced guys.
For reliability and long as possible service, good fuel, timing set to 26*, never overprop (probably not possible with your small boat). Overall timing needs to be set under a load at 5500 rpms. I would lap the flywheel to the crankshaft taper. Check the crankshaft seal and make sure the bearing cap bolts are tight. Also make sure there aren't any loose magnets inside of the flywheel. These motors are getting old and the magnets do pop off. I would go up 4 jet sizes from stock because there is so much alcohol in fuel now compared to the 80's.
I really don’t know for sure if the XP has any more horsepower than a stock 235 but others might. And I don’t know anything about the ultrasonic cleaners. I’ve never used them. I do like to run Sea Foam in every tank to keep the fuel system clean. I always run 93 octane in all my motors. Good luck.
Yep, I remember setting the timing on my 175hp crossflow with a borrowed test wheel at the boat launch. The onlookers thought I was crazy. No one even knows how to work on anything or tries.Quote:
Originally Posted by john j 80 viking
What is factory timing? I tried to find it in my manual but I couldn't find the spec anywhere! Really bothers me. The OMS manuals from that era are so horrible. Is 26 deg advanced? What does that do for the engine?
Are the magnets riveted on? If they are on, do you see them starting to come off or are they just on or off? That sounds catastrophic. Should I be mixing up some epoxy as a preventative measure or something??
Jet sizes...I run only rec fuel with 0 ethanol. Do I then even need to bother with changing jets? I don't have experience with that. Where do you get your replacement jets from?
Thanks bud. It will be a little project next year. I'm excited. I have never seen one of these engines. I'm wondering in stock form how fast thing thing is going to push that 16 ft Checkmate!Quote:
Originally Posted by 97mirage
Originally OMC had spec the timing at 30*. They later reduced it to 26*, I'm sure to reduce warranty issues. You should be confident timing your motor to 26*. The magnets are epoxies on. They get a little rust behind them and pop off. You could do some plug checks to check that your jet size is ok. If it were me, I would still go up a few sizes. Not sure where to get jets anymore, now that OMC is gone for good it seems.Quote:
Originally Posted by sootypipe
I would say 26 degrees max on a heavy boat, premium fuel ONLY. And that depends on the heads and cranking compression.
My XP and mod 235s were 128 to 130 psi. I set them at 26 degrees and ran them a bit rich.
And RPMs. LOL!!! Yea, there is a range where there is a harmonic vibration. As said in the 6300 to 6500 range. But I found the old 235s/2.6 motors could run 7,000 on a light boat all day if you tune it right. Even with cast pistons and stock rods. Just blow past the "no go zone!" and let her rip!
https://www.youtube.com/watch?v=_rHWWiMiA4U
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).Quote:
Originally Posted by Forkin' Crazy
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?
How do you get past the 6200 rpm limiting power packs?
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?
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.
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.Quote:
Originally Posted by 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.
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.Quote:
Originally Posted by LakeFever
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?Quote:
Originally Posted by john j 80 viking
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?Quote:
Originally Posted by Forkin' Crazy
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.Quote:
Originally Posted by sootypipe
Interesting that even in the two years of the 2.6 XP/GT, they jetted the carbs differently!Quote:
Originally Posted by Forkin' Crazy
theres a few good threads on this process. This one has pics its pretty easyQuote:
Originally Posted by sootypipe
https://www.screamandfly.com/showthr...wer-mtr-mounts
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.
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.
I think my 2.6 XP was an ‘83.
Quote:
Originally Posted by sootypipe
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.
I think I set mine at 26. That was with 128 to 130 cranking compression.
Keep her fat, and she'll stay happy. I started out a few sizes rich because of my mods. It was 4 stroking and blubbering at first. But I jetted smaller one size at a time until it cleaned up, and left it alone.
ALWAYS run premium fuel and the best oil you can buy.
I wish I had a dollar for every hour I put on that old 1980 235. And both of mine are high ring motors. So there goes that myth!
I think that OMC changed their original timing spec from 30* down to 26* once they realized how these motors were easily damaged by crappy fuel and lugging on heavy boats. I agree that timing to 26* will give up very little performance and make it more tolerant of poor fuel and poor running conditions.Quote:
Originally Posted by Forkin' Crazy
I can't agree with you on the high ring piston thing. The two 235's that I've had on my Viking were both run very hard with the tight heads for hundreds of hours each put on them, and the point of failure for them both was high ring pistons. I rebuilt motor#1 and could not reuse several other pistons in it because the top ring groove was ready to fly off. Motor #2 hasn't been disassembled yet, but that one has 2 pistons with no top rings in them. Maybe my high ring piston problems are from long runs at high rpms? Just trying to keep up with all those fools with black motors on their boats.
Is the C series and D series naming from OMC or from a supplier of the actual carburetor? Like do you know if those 2 barrels were made by OMC or were made by Tillotson like the old Mercs or some other supplier?Quote:
Originally Posted by racer
So if I’m going to keep the internals (and everything else) of the engine stock and aim to run it at 6200 rpm, retard timing to 26 deg, then do I need to worry about replacing jets? I have no idea where to get them since they are nla, especially multiple sets of different sizes! And I run no-ethanol rec fuel which around SE MI is always 91 octane. I’d say that’s mid grade but not high octane. But I don’t want 93 octane auto fuel with 10-15% junk ethanol in it! Oh, and I use full synthetic Evinrude xd-100 oil, 50:1 in this engine.Quote:
Originally Posted by Forkin' Crazy
I think the problem was lugging with heavy boats combined with too much compression. Detonation was the problem, not the high rings. I still have two high ring V4s, an Evinrude 140 and a Javelin 100 that have never had the heads off of them.Quote:
Originally Posted by john j 80 viking
OMC started using looser heads AND had a revision for thicker head gaskets to patch up the "problem". I was working at an OMC dealership at the time.
You put a small enough prop on it so it was not lugging, no problem.
I have two 2.6s I built both with the tight heads. 325638 and 325639 if I remember right.
I ran this totally stock cast piston XP with high rings and never had a failure because of ring location.
I think that was a detonation issue, not a design issue.
https://www.screamandfly.com/attachm...2&d=1669531125
This one is still together. 7K all day.
Attachment 512722