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Thread: v6 crossflow hesitation
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02-15-2011, 12:02 AM #315000 RPM
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What is the engine timing when the carb roller just bisects the line on the throttle cam?
Does the timer base rotate freely or does it drag a bit when you advance the throttle both fast and slowly?
What is your top rpm with a normal load?
Not idle timing, that is what changes your idle rpm. If you are sure that the sync and link has been done correctly, then slowly advance the throttle until the line on the cam just touches the middle of the throttle roller and starts to open the throttles - now check the timing at that point.
When the carbs were cleaned, did you remove the mid-range jets from the float bowls and clean them? Since they are buried inside the float bowl - not to be confused with the high speed jets - many folks do not know about them so they never get cleaned out and the motor will not accelerate correctly.
Does the timer base move freely and not compress the throttle lever spring until the timing stop is touched?
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02-15-2011, 09:33 AM #32
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02-17-2011, 07:33 PM #33
Did the linc and sync precedure again and the pickup timing was way off, the manual called for 7* and it was at about 3.5*, so that was hurting me for sure, but I also found that someone had put the wrong plug wire on cyl #2, the boot was to long on the coil side and wasn't making a good connection, trimmed the boot down and fixed that maybe i'll get a chance to put it in the water tomorrow but it definitely sounds better on the hose in the yard and seems to rev quicker.
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02-20-2011, 09:20 PM #34
Took the boat out today and it was alot better wouldn't bog when getting on plane hardly at all but I could still make it bog and stall out when powering it on the trailor, I guess I'll pull the intake off next and check for leaks, doesn't look like its ever been off still has the paint on and around the bolts.
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05-24-2011, 08:59 PM #35
Pulled the intake off tonight and everything looked fine so now im at a loss, checked the recirculation valves and hoses and all were flowing and closing like they should, i'll check the intake for straightness tomorrow but the gasket mark didn't show any leaks.
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05-25-2011, 03:51 AM #366000 RPM
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It's important to have the throttle cam and roller adjusted properly, (sync and link) for throttle pickup. The specific idle timing should not matter, as it will vary-depending on how deep your engine sits in the water on your particular boat. It will vary between boats due to engine mouting heights and how deep your boat sits with the engine on it. The idle timing should be set so that your engine idles between 650 and 750 rpm when floating normally in the lake while in forward gear. When you had the carbs apart, die you pull all the jets for a visual inspection? What are the compression numbers for your powerhead? You may be overpropped-hard to tell without a max rpm tach reading.
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05-25-2011, 08:41 AM #37
I posted the compression numbers earlier in the thread but they were in the mid to upper 80s so I believe it has the low compression heads, could it be that it is over propped with these heads? Had the heads off when I first bought the motor replacing the head gaskets and the cylinders looked pretty good.
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05-25-2011, 03:01 PM #385000 RPM
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05-25-2011, 08:52 PM #39
I think this motor only had around 90psi new but correct me if im wrong. Got the intake back on and sealed up, pulled the carbs back apart to recheck, they are clean and all of the mid range jets are flowing fine, but all three float levels were a little low, the tip of the floats were about an 1/8" higher than level with the gasket surface with the carbs held upside down, fixed that so we'll see.
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05-27-2011, 11:52 AM #40
Got it back together and running, readjusted the throttle cam and follower, and it runs the same, you can hear a miss while idling on the hose that gets worse the longer it idles, the center cylinder on both sides seem weak but are getting spark and fuel, pulling the plug wires one at a time the center cylinders don't change the idle much where as the other four almost choke it off. Im gonna do another compression test then test it again once it's warm, maybe it has a ring tention problem that comes with heat, it always runs pretty good when I first start it up.
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05-28-2011, 12:50 AM #41
It sounds to me like you need to play with your air jets. The very high ammount of alcohol in the fuel these day is screwing every thing up. There is some great trouble shooting for crossflow motors in the 9 pages which can be found here http://www.screamandfly.com/showthre...w-Thread/page2
I used to have trouble getting back on the trailer untill I changed my air jets.NRA Life Member
58' Farmall Cub
Is that your mama's boat?
"I said I didn't have much use for one. Didn't say I didn't know how to use it."- Mathew Quigley
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08-09-2011, 09:18 AM #42
I messed with this motor again this weekend, just seems strange that it runs so strong at wot and so weak down low, the boat is about 700lbs and runs 66mph w/a 25p prop, I think that's pretty good for an old crossflow, but just cruising around I can let off the gas for a second then stab it back and hear it sputter for a split second before it revs back and starts pulling, one guy said it could be the low side of the stator going out could that be possible?