Reed valves

[Aquafeeder]

Having trouble with my 2001 merc carbureted getting over 1200 rpm under load. Starts , idles , no issues with motor when not under load . Will not get over 1200 under load. Did ever test that I know of in fuel, electrical , etc. rebuilt carbs, new fuel pump,all lines and ball, tank check valve. Took out reed valves and they look good. Not noticing carbs spurting gas but have low pressure 2 lbs or less on 2 ports. Anyone with ideas? Can anything else cause low reed pressure? Compression good!
Thanks

 

[Faztbullet]

Re: Reed valves

Reeds are either good or bad. Where are you measuring this 2 psi pressure? Sounds like you still have a electrical problem or compression issue as this engine will run on 3 cylinders and sounds ok and rev's up without a load.Also check to see if high speed jets was installed in correct positions .If in my shop I would check in this order:
1) compression...if any below 100psi on any cylinder that cylinder head is coming off for inspection.
2) ignition...is it firing on all 6? Check with gap tester at 3/8 minimum and should be blue with a "pop"
3) fuel system check and jet check
4) check prop pitch as if too big or vent holes are incorrect will cause similar symptom especially on the small gearcase
5) check linkages to ensure trigger is advancing fully and carbs are at WOT in sync with controls
6) if everything checks out itt lake test on trailer, checking spark with timing lite to see if cylinder/s are dropping out. inspect fuel flow in carb throats and if still not running pull lower unit to see if tuner fell off as it will need one on a Nitro hull.

 

[sam am I]

Re: Reed valves

Can anything else cause low reed pressure? Compression good!
Thanks

If comps and reeds are okay? ("Check for wear (indentations) on face of each
reed block. Replace block(s), if reeds have made indentations."),

Then seals on the underside of the rings would be suspect, including but not limited to crankshaft sealing rings, crankcase split line seal, end caps, gaskets etc.........

 

[Dukedog]

Re: Reed valves

Agree with Fast. Sounds like tha ecm.............

 

[Aquafeeder]

Re: Reed valves

Thanks for your ideas. I've been at this problem for 5 mos!. I'm
Starting over again! Compression good. Did spark test getting 7/16 spark all plugs. Did CDM test, stator, trigger . Checked all wiring! I took it in to local boat shop which I'm not to impressed with and they said all electronics were good. They said carbs needed rebuilt running to lean?
I rebuilt carbs didn't help. The problem is I have to take it to lake to test under load! Alot of trips so far. One thing that puzzles me is the plugs are wet which to me tells me they are getting fuel. The spark is good CDMs check good. But when motor is running even on muffs I can pull plug wires and to me only firing on 2 maybe 3 cylinders. Can it fire out of sync like with points? Is a nitro hull never heard anything about exhaust tuner? Thanks again and like I said I'm going to start over and touch on all your ideas . One thing I might mention , with but I trailer dies at 1100 rpm , pumping ball doesn't help but sometimes which holding in enricher and playing with throttle it will get to 2500 which might be normal under those conditions?

 

[Faztbullet]

Re: Reed valves

he spark is good CDMs c

Check by the CDI/Rapar test procedure as these modules will make you cuss and hard to troubleshoot as one down the line can make 2 or 3 others act goofy.

 

[sam am I]

Re: Reed valves

Not going to dwell on this but, you said "2 lbs or less" on two ports reed pressure and now report "pulling plugs" and not having the motor effected by the lack of a few cylinder's not firing? Hmmmmm

Are those plug wires cylinders you're puling the ports with the low reed pressure?

Book says "3 to 6 psi idling". Anything less is an issue. I assume you measured these pressures as per manual? If so.........seems to me you've went through everything A-Z once or twice and those things are APPEARING okay BUT, never addressed why (or the effect there of) you have such low reed pressure.....

You also report the enricher tends to get the rpm's up a tad.....would seem to me that these all relate.

If you have low reed pressure in a few ports then I would hazard a guess those particular cylinders aren't getting the right amount(they're starving) of fuel.........and perhaps the enricher test you've reported is indicating this by dumping excess fuel in, you said the RPM's go up and........in addition, your other test of pulling plugs might be in fact, on those particular low/starving fuel cylinders, it's not making the engine crap out(change much) because they are pretty much "running dead" due to the fact, they're not getting much fuel to begin with, you said pulling plugs seems like only running on some cylinders.

As a test.......identify the cylinders that have low reed pressure, put it on trailer(or muffs), fire it up, spray some pre-mix gas directly into just those cylinders and see if RPMs go up significantly relative to spraying into cylinders that have normal reed pressure.....I'll bet the low reed pressure cylinders bump the RPM's way up as opposed to the others......

This should indicate that in fact those low reed pressure cylinders are dragging due to low fuel issues.......Just taking a shot here I suppose, I certainly could be just blowing smoke.......

 

[Dukedog]

Re: Reed valves

ECM went south!......it controls pretty much everything.