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  1. #1
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    LOOPER TECH TIP's.........

    Thought this might me a fun idea for some of you trying to keep these old dinosaur's running.
    In struggling to get the 250 HO looper's running right that I built for the Sonic and now the 250 stocker's that I bought to temporarily replace them I've run across some of the odd ball issues that don't show up very often and most are not in a manual. They can stump you if not careful/lucky and figured this would be a good way to document them for others future benefit.
    Also, any of you guys that have run across similar odd ball head aches or have comments on what I've found/done, feel free to add to the list. Not meaning for this to be a BS session or a place for you to post your problems for us to solve but kind of a reference point to "search" when you get stumped on something along the way.

    Be very interested in comments from Racer and any of the other OMC Wizards on board.

    Here's todays list.

    #1. Stators melting the insulation that runs down on top of the powerhead, under the flywheel on old motors. Most of us have seen this numerous times but on the motors I just bought one of my issues was the port motor shutting off under acceleration. Stumped me for a while until advancing the throttle w/the cowling off I notice it appeared that the timer was not rotating/advancing timing?? The stator gooh had glued it stationary and the spring in the idle timing adjuster allowed the the rest of the linkage to function normally!
    Cleaned the timer and cured that issue and motor now accelerates! Still more issues and yes it needs a stator.

    #2. Main jets. as we all know these carburetors are plastic and we have to be careful w/them. They had a reputation of coming from the factory w/the main jets loose enough that they would actually vibrate out! Just rebuilt all 12 carb's off the new motors and all 12 were loose!

    #3. Carb couplers. This is a good one and one that will piss you off! On the V-6's the top and middle carb's share a throttle shaft while the middle and bottom carbs do not. These carb's are connected by a flexible coupler attached at the stub/bottom of the throttle shaft under the middle carb and the top of the bottom carb. W/time and hrs these vibrate loose enough (usually not visibly) to allow them to move. What happens is the top 4 carbs will open and one or both of the bottom two will stay or vibrate closed.
    I watched this happen on my old Sonic w/one motor driving me nuts. Had some one drive the boat while I watched the motor w/the air box off. All 6 opened and then one of the damn things vibrated closed! Wouldn't have believed if I hadn't seen it. Also just happened on the same motor w/the acceleration issues.

    #4. Carb vacuum plates. This is another good one. Chased my tail in circles for wks on a motor that had me stumped. The motor would not pull fuel from two of the carbs no matter what I tried.The carbs have these small plates on the throttle bodies and carbs themselves w/a small rubber gasket under them. They are attached by small phillips screws. Two screws on two plates had backed out maybe a 1/4 turn (not visible) and a I caught this after tearing the damn carbs down for the umpteenth time. A light bulb went off, I tightened the screws ad cured the problem.

    #5. Starters and cranking speed. I was told this yrs ago when I first started playing w/this crap and didn't believe it until I saw it. The way the starters are built they allow oild to get on top of the armature of the motor. We all want to lube the shaft and bendix but then after a while it builds up w/no where to go but down. It seeps past the dust cover and then works it's way on to the top of the armature. These armatures have the brushes making contact on the top where this oil is and they don't like it at all. I see this in probably 50% of the motors I putz with. Of those, probably 95% can be fixed w/o replacing parts. Normally all they need is cleaned.
    When there's an issue this will normally DOUBLE your cranking speed w/o doing anything else! What makes this important is when you are diagnosing ignition components w/cranking tests. Slow cranking sped will fail them all! I had this issue w/the above motor. My cranking tests were telling me I had ignition issues until rebuilding the starter then everything passed!

    #6. Carb emulsion tubes. These are the small tubes sticking up, into the carb throats. When the throttle plates open and engine speed picks up the carbs pull a vacuum to pull additional fuel from the float bowl through those tubes. I just found 3 out of the 12 carbs I rebuilt on the new (200 hrs!!) motors that had slipped down into the carb body.
    I'm weak on cause/effect on this one but would guess motor would be starving for fuel in this situation. Factory manual says nothing.

    #7. Engine Tuner or similar chemicals. This stuff is the **** and way under utilized! I've opened up probably 30 or more V-6 looper donor motor's in the last couple yrs. 99.9% of these motors had one bad hole (99% of those were on top) and 100% of those was from detonation. Not running lean.
    With time, the oil starts to "coke" (turn to gum) and sticks the rings into their grooves (ring lands) in the piston. Once that happens we now have flame propagation blowing by the compressed rings (stuck in the piston) and burning the remaining lubrication oil off the piston/rings/sleeves. Once this happens you're done! Combustion chamber temp's go up, and the makings for dtonation are text book perfect. Add to this a worn/weak water pump, crap gas, high loading (wrong prop, too much weight in boat) etc, etc and your done. Course this is another symptom often written off to faulty VRO's but mysteriously is ALWAYS (my experience) one hole only.
    "Engine Tuner" is a solvent you induce to the engine through the carbs while running. (just like winter fogging for you guys up north)
    Let it set over night and it eats this gum then pukes out the exhaust when you start it the next day.
    I have been using "Seafoam" and having real good luck w/it because you can get it on sale at auto Zone for $9 or $10 a can. The actual Engine Tuner though has a hose that attaches to the primer and allows you do all 6 at once which is pretty slick. IMO, this is maybe the most under advertised, under used preventative maint. item we have.
    I attached a pix from one of the 200 hr motors I did last night. The photo doesn't do it justice as I allowed the crud to sit over night and most of it broke down. The silver color on the cavitation looked like someone threw up on it last night! The black on the ground was not there before doing this. IMO, if your motor is now solid internally, you run decent gas/oil and run this stuff a couple times yr....., your motor should last a long, long time!

    <a href="http://s290.photobucket.com/albums/ll255/Instigatorspixs/?action=view&amp;current=enginetuner.jpg" target="_blank"><img src="http://i290.photobucket.com/albums/ll255/Instigatorspixs/enginetuner.jpg" border="0" alt="Photobucket"></a>

    #8. Top two cylinders run hot and lead to catastrophic detonation. I eluded to this in #6 above. Common wisdom says that due to really poor exhaust scavenging on the bottom two holes of a V-6 looper, those holes run hot and they do. But the factory put's 2 cc's of additional combustion chamber volume (why compression is 5 lbs lower on those two holes) in those two (one on each side) holes to combat this and IMO this works pretty well.
    I think at least 99% of the dead V-6's I've opened up have had a dead #1 or #2 on the top. My opinion is that the block struggles to stay filled with cooling water in that area. I and others have done a bunch of work to combat this on the hot rod motors.
    Some potential issues are over heating which causes the cooling water to boil (inside top of block) which makes steam and that equals pressure which fights the cooling water trying to get there. Once that happens we're back into detonation prime time!
    I can tell you that EVERY one of my hot rod motors I've popped since being down here has been from detonation (all from inadequate octane levels which was my fault) and ALL have been a top hole. I think a worn water pump (excess motor height) can start this and if you have ring sticking/coking beginning also, you're done!
    Once my motors are dialed on the Sonic they will both be jetted 1 step higher on #1 and 2.

    #8 and last for now. Carb idle jets. On these motors they only flow air and no fuel. They can build up crud inside their bore and restrict the passage. This will make your motor run rich and smoke at idle. Found several in the carbs I just rebuilt for the 200hr motors. They weren't totally blocked so the motors still idled pretty decent but once the jest were out you could see the difference w/the naked eye after blowing them out w/compressed air.

    There you go kids. Hope you enjoy it cuz it took me 1/2 a day to type it
    Last edited by Instigator; 07-29-2011 at 05:27 AM.
    I'd rather be competitive w/junk I built in my garage than win w/stuff I bought.


    I refuse to allow common sense to interfere w/my boat buying decisions.


    Checkmate 16' 140 Johnson
    Hydrostream 17' Vector FrankenRude I
    Laser 480 (?) 21' w/GT 200
    Glastron Carlson Conquest w/XP 2.6
    Glastron Carlson CVX 20 w/XP 2.6
    24' Sonic w/twin 250 Johnsons
    24' Sonic w/twin 250 HO Johnsons
    19' STV River Rocket w/FrankenRude II
    Allison XR 2002 w/Frankenrude II
    Hydrostream 18' V-King w/Frankenrude II

  2. #2
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    Good post...... Also, Engine tuner is great for cleaning carbs as well while your'e rebuilding them. I get the stuff by the gallon and have a paint can to soak the carbs in....
    "One of the penalties for refusing to participate in politics is that you end up being governed by your inferiors". Plato .

  3. #3
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    Do one for Eagle engines please.

  4. #4
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    Great post,lots of useful info there.
    21 SuperBoat VF200 Yamaha SHO
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  5. #5
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    What can you do to keep the top cylinders cool, Will 87 octane kill one of these motors?

  6. #6
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    Thank you Gary for taking the time to do this! Im sure lots of "white" guys like myself appreciate your time!

    BTW, Hope you dont mind that I copy/paste this and save it to "my documents"!!!

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  8. #7
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    I'm sure more great info is gonna be posted here!!I'm subscribed and watching closely
    1986 Hydro Vegas w/260
    1980 24' Superboat w/300 PM (Sold)
    1986 20'Taylor LP w/300 promax (Sold)
    1986 10' Cougar Cub w/25 Johnson (Sold)

  9. #8
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    Your probably one the best OMC guys around, based on a the little things you have found like this stuff, that will make you want to pull hair out.

    I will add on the seafoam you can also use the 1 gal lawn mower can and after warm up just stick the fuel line in the can and follow directions. On V4's you can use the Deep Creep spray which is the same stuff but v6's too many carbs
    Last edited by Eggsuckindog; 07-28-2011 at 11:11 PM.

  10. #9
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    I would like to add two hints to clarify two items mentioned by Instigator.

    1)
    About the high speed jets coming loose, they can make you tear your hair out because they can back out against the carb drain screw and restrict the flow of fuel (and lube oil) to that cylinder. They can vibrate in and out continuously making you scratch your head looking for the problem as the one cylinder develops power then starves for power, then comes back again. The fix is to install the late model carbuetor drain screws that have a notch in the end of them. That way if a jet backs out of the carb, only the edge of it will hit the drain screw and fuel will still flow to the affected cylinder, saving a powerhead.

    2) Those side cover plates and gaskets that can leak air are easily tested. Use a spray solvent such as Evinrude Engine Tuner or a carb cleaner spray, and use safety glasses to protect your eyes. Fit a small aerosol can "straw" such as a red one from a WD-40 can to the solvent spray can and insert it into one of the air jets on the front of the carb. Shoot the solvent thru the jet and it will build up a little pressure inside the cover passageways and will leak out any gaps in the gasket. It's a quick test of the integrity of the idle and midrange circuits. If there is leakage, sometimes it's from a distorted cover plate or a reused gasket. You can straighten the aluminum plates on a flat surface and use #10 washers or better yet, fender washers, to add more clamping area to the cover. That makes for a quick cheap fix for poor acceleration or a hard to find sneezing at idle problem.

    .
    Last edited by seahorse; 07-29-2011 at 06:10 AM.

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  12. #10
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    Quote Originally Posted by seahorse View Post
    I would like to add two hints to clarify two items mentioned by Instigator.

    1)
    About the high speed jets coming loose, they can make you tear your hair out because they can back out against the carb drain screw and restrict the flow of fuel (and lube oil) to that cylinder. They can vibrate in and out continuously making you scratch your head looking for the problem as the one cylinder develops power then starves for power, then comes back again. The fix is to install the late model carbuetor drain screws that have a notch in the end of them. That way if a jet backs out of the carb, only the edge of it will hit the drain screw and fuel will still flow to the affected cylinder, saving a powerhead.

    2) Those side cover plates and gaskets that can leak air are easily tested. Use a spray solvent such as Evinrude Engine Tuner or a carb cleaner spray, and use safety glasses to protect your eyes. Fit a small aerosol can "straw" such as a red one from a WD-40 can to the solvent spray can and insert it into one of the air jets on the front of the carb. Shoot the solvent thru the jet and it will build up a little pressure inside the cover passageways and will leak out any gaps in the gasket. It's a quick test of the integrity of the idle and midrange circuits. If there is leakage, sometimes it's from a distorted cover plate or a reused gasket. You can straighten the aluminum plates on a flat surface and use #10 washers or better yet, fender washers, to add more clamping area to the cover. That makes for a quick cheap fix for poor acceleration or a hard to find sneezing at idle problem.

    .
    Great addition. Perfect. Thanks.
    I'd rather be competitive w/junk I built in my garage than win w/stuff I bought.


    I refuse to allow common sense to interfere w/my boat buying decisions.


    Checkmate 16' 140 Johnson
    Hydrostream 17' Vector FrankenRude I
    Laser 480 (?) 21' w/GT 200
    Glastron Carlson Conquest w/XP 2.6
    Glastron Carlson CVX 20 w/XP 2.6
    24' Sonic w/twin 250 Johnsons
    24' Sonic w/twin 250 HO Johnsons
    19' STV River Rocket w/FrankenRude II
    Allison XR 2002 w/Frankenrude II
    Hydrostream 18' V-King w/Frankenrude II

  13. #11
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    Another hint for these blocks that have a pressure relief valve on the back of them between the thermostats, '93 and later, I believe. Early models had a solid plastic cone-shape valve and '97 and later models has small grooves in the valve to help bleed air from the block when starting up. Remove the valve and drill a 3/32" hole in the center of the cone. That way air will be expelled quickly to help fill up the block with water, plus it bleeds off airbubbles that get trapped at the top of the block which affect cooling the upper cylinders and the water-cooled voltage regulator.
    Last edited by seahorse; 07-29-2011 at 08:24 AM.

  14. #12
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    Quote Originally Posted by seahorse View Post
    Another hint for these blocks that have a pressure relief valve on the back of them between the thermostats, '93 and later, I believe. Early models had a solid plastic cone-shape valve and '97 and later models has small grooves in the valve to help bleed air from the block when starting up. Remove the valve and drill a 3/32" hole in the center of the cone. That way air will be expelled quickly to help fill up the block with water, plus it bleeds off airbubbles that get trapped at the top of the block which affect cooling the upper cylinders and the water-cooled voltage regulator.
    Great trip.
    On the hot rod motors I am drilling and tapping ports on the top of both sides of the block just forward of the heads for same reason. Plan to do that on the Sonic motors as well.
    Another thing I'm playing w/is replacing thermostats w/washers and using them as restrictors in place of the stat's. Issue is getting the holes size correct. Small = good pressure but less water to heads and large = less pressure but plenty of water to the heads.
    Our water temp in the Intracoastal is about 85* now and the motors are running about 160 even w/133* stats in them and I'd rather see mid 140's but not sure that's possible.
    I'd rather be competitive w/junk I built in my garage than win w/stuff I bought.


    I refuse to allow common sense to interfere w/my boat buying decisions.


    Checkmate 16' 140 Johnson
    Hydrostream 17' Vector FrankenRude I
    Laser 480 (?) 21' w/GT 200
    Glastron Carlson Conquest w/XP 2.6
    Glastron Carlson CVX 20 w/XP 2.6
    24' Sonic w/twin 250 Johnsons
    24' Sonic w/twin 250 HO Johnsons
    19' STV River Rocket w/FrankenRude II
    Allison XR 2002 w/Frankenrude II
    Hydrostream 18' V-King w/Frankenrude II

  15. #13
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    I just gutted my thermostats because they were stuck open, I put the spring and the washer like piece with the hole in it back in. Ill be sure to see how it cools. Goint to run through some of there tips and see if any of them are the cause of the prob I'm currently having.

  16. #14
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    Can you show pics of the tapped ports on the block for cooling you said you were doing? Another ?, the pressure releif valve has a washer that goes with it, one side says to cylinder head, if you put it in that way it seals tight around the cone, the other side is tapered like the cone and has little (blocks) around it so it doesnt seal tight and has a small bit of space between the cone and washer. I'm thinking that turning the washer around would do almost the same as the the hole, right now the washer is put in with the cylinder head side out so its seals tight with the cone, (thats how I was told it was supposed to go in).
    Last edited by Gorilla0178; 07-29-2011 at 09:17 AM.

  17. #15
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    Gary, I enjoy your reading and projects. That said will the engine run on 100% seafoam? I'm thinking of doing that on my 300xs at idle to keep the injectors clean and carbon free rings.
    Checkmate 2002 Convincor 270 496 MAG-HO

    2003 Cougar 22MTR w/300xs SOLD
    90 21Skater w/300xs - sold
    98 STV Euroski w/280 - sold


    2006 Trailblazer SS 6.0l 395hp

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