1984 Mercruiser GM 350 engine no start, not even trying to fire

Discussion in 'Powerboats' started by sdowney717, Aug 19, 2022.

  1. sdowney717
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    sdowney717 Senior Member

    Beginning to wonder if valves are stuck open.
    Engine is portside, so should be standard rotation.
    Distributor turns CCW, is that correct?
    And what is the firing order? 1-8-4-3-6-5-7-2 ?

    What is compression range for GM 350 MCIE 260 Mercruiser?
    What is the spark timing?
    I pulled wires and took off cap and everything looks ok, the rotor does not come off.
    I static timed by putting cyl #1 at 8 degrees BTDC and turned distributer till it fired the spark.
    I did all that after it has continually refused to fire.

    History of engine is owner badly flooded engine to the point of the oil level rose way high on dipstick when he was trying to start up, and he burned out the starter. That problem was caused by needle valve in quadrajet laying in float chamber. I repaired the carb, no more flooding. Oil changed, and now no fire, no start. Appears to have very good spark. We changed the spark plugs. Other observation is when cranking some gas is thrown up out of the carb from the intake manifold Stuck intake valves??

    Pulling spark plugs and they are dry. Beginning to wonder is engine has lost compression due to intake valves stuck open.
    Plan to check engine compression next
     
  2. sdowney717
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    sdowney717 Senior Member

    20220807_092434 (1).jpg This is the engine
     
  3. fallguy
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    fallguy Senior Member

    Assume you changed oil.

    try disconnecting the battery and see if you can turn it all the way through by hand, use a 1/2" socket wrench and ?15/16"? iirc socket or one that fits
     
  4. fallguy
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    fallguy Senior Member

    When fuel leaks down, these engines can hydrolock. When they hydrolock, they can bend a rod pretty easy. A hard spot when hand turning will indicate a bent rod and rebuild time.
     
  5. sdowney717
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    sdowney717 Senior Member

    Interesting about bending a rod.
    I turned it somewhat using a pipe wrench on the front pulley enough to align the timing marks.
    A compression check should also show a problem. I have had pushrods bend with stuck intake valves in several GM engines.
    It is odd that small amount of gas spits back out of the carb when cranking. Makes me think an intake valve(s) stuck open and forcing air out of the intake on compression strokes. Will know about compression test in a few days.
    Yes, oil is new.
     
  6. sdowney717
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    sdowney717 Senior Member

    Does anyone know which direction the distributer rotor supposed to spin?
    I am seeing conflicting info, GM 350 seem to all spin CW, yet this engine is turning CCW.
    He replaced the starter when it burned out, is the wrong rotation starter on the engine?
     
  7. fallguy
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    fallguy Senior Member

    Firing order tells the rotation.

    -> from the google Gods

    Re: How can I switch from R to L rotation on a Chevy 350 V8

    Is there a sterndrive bolted to this engine. Sterndrives use left hand/standard rotation engines. Standard and counter rotating engine the distibutor rotor turns clockwise. If you put the wrong starter in the rotor will turn counter -clockwise. Right hand engines. Piston go in different. Camshaft different, timing chain seal is different rear main is different. firing order too. Crankshaft nurling on two piece rear main seal engine. nurling goes oppisite direction. Fire order std. 18436572 counter 12756348.
     
  8. fallguy
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    fallguy Senior Member

    ...that should tell you everything...

    except if the fella bent a rod trying to start an engine with lots gas in the wrong places...
     
  9. sdowney717
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    sdowney717 Senior Member

    inboards.

    yes firing order tells that, but it is not noted anywhere on the motor. From what I have been reading one uses gear driven camshaft, other uses chain driven, that allows the distributor to turn the same direction on both. I am also reading all GM distributors turn CW, meaning he must have put the wrong starter on. Unless the people saying that are wrong.

    Only a few velvet drives allowed either rotation to be used full time without switching the oil pump.
     
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  10. fallguy
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    fallguy Senior Member

    I'd probably contact a starter shop. Play dumb and ask them what starter to use and which way it goes..
     
  11. Scuff
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    Scuff Senior Member

    Couldn't they have just used a cam ground for the counter rotation? If it bent a rod or two it should still start and run.
     
  12. fallguy
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    fallguy Senior Member

    It won't start if the starter is reversed as it appears.
     
  13. DogCavalry
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    DogCavalry Soy Soylent Green: I can't believe it's not people

    Have you confirmed direction of rotation for this engine? Look at the cam/crank connection, if no better way suggests itself.

    I was going to suggest taking off the valve covers and look, but compression test is a lot easier. If it's cranking but not firing, you should be huffing out a lot of gas. Valves stuck open would blow back through the intake. Valves working you'd be pumping fuel/air mix out the exhaust. Obvious stuff I know, but that's troubleshooting. Systematic elimination of possibilities.
     
  14. sdowney717
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    sdowney717 Senior Member

    Yes, marina parts guy sold him the wrong rotation starter. I have a couple other threads on boat forums going about this.
    It was a re-learning experience for me.
    He has ordered a CW starter from Amazon for $60 less than the local boat store.
    He can still use the wrong new starter on his other starboard engine as it must spin LH and would use a CCW starter.
    1984 Mercruiser GM 350 engine no start, not even trying to fire - The Hull Truth - Boating and Fishing Forum
    1984 Mercruiser GM 350 engine no start, not even trying to fire | Boating Forum - iboats Boating Forums
     

  15. sdowney717
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    sdowney717 Senior Member

    He was totally lost and still is in a way about his engine. His engine broke couple months ago. And it takes a lot of time to figure out what other people have messed up, like being sold the wrong starter. That had me stuck for a week. All I had was like a few hours of free time to help him per week. But now I understand what happened, means I can also make it run again.
    Being reverse rotation means fire order differs, and since I move distributor, will have to static time to 8* ATDC on the crank, ATDC as it is turning the other way.

    TTaxi has a lot of good info, has helped me out before.
    ============================================
    To answer your question about RH engine firing order specifically :

    "The firing order for a ( in this case RH 5.7L 350ci) Chevy marine engine that makes a reverse rotation is 1-2-7-5-6-3-4-8 ."
    It is the opposite of the standard rotation firing order, but still in CW sequence on the dist. cap from #1 post. Rotor must aim at the #1 cyl dist. cap electrode post when engine Cy. #1 /front port side is TDC on the compression stroke.

    --------------------------------------------------------------------

    These are twin inboards with standard LH and opp .RH engines , ( not both same rotation engine as has been the case with I/O's for a very long time. )
    As noted a few times above, both the standard /LH/ CCW ( as viewed from the flywheel end toward pulley end) -rotation GM 350 C.I./5.7L engine and the opposite/RH CW rotating engine should have CW-turning distributor shafts.

    If, as you say, your RH-rotation engine's dist. shaft is turning CCW, you have the wrong rotation starter installed and that can suck sea water ( or muff/hose water ) into the cylinders and hydrolock them and cause serious damage. Don't crank it any more and get the right starter . Depending on mounting position (pinion gear forward, or aft end) , the correct starter for that RH engine could beeither RH or LH as viewed from the starters gear end.

    The ARCO Marine catalog has a really helpful diagram to guide you to choosing the correct rotation starter for your engine.
    Look carefully at the illustration on page 28. https://www.marineengine.com/parts/arco-marine-parts/catalog/ARCO-Marine-Catalog.pdf
    Note the circular arrows denote engine rotation only , not the propeller rotation !!

    Apparently your series 71c or possible 72c Velvet Drive transmissions likely have 1.88-1 or 1.91:1 reduction and those models have reverse output to the prop shaft, so as on my twin 5.7L I/Bs with VD 72c 1.99:1 gears, the standard LH rotation engine is on the stbd side of the boat and the prop on that side turns RH clockwise which is reverse of engine rotation. If they are Velvet Drive 71c ( or 72c) transmissions with those specific reductions, the propshafts for both the LH and RH rotation engines will turn opposite of engine crankshaft rotation. Your presumably-still-starting and -running standard LH/CCW engine will make that obvious when put in Forward gear and the RH prop spins CW as it should .

    So - for the no-start engine on your boat's port side which apparently is a RH engine with LH/CCW prop , use the engine shown at the top right side of the illustration on p. 28 to match the starter orientation and determine whether you need a LH or RH starter.
    Or ... just get the opposite rotation starter from what you have now. Ignore engine rotation when actually buying the starter.

    Hope you don't have water in the cylinders yet. If not, your engine should start a lot better turning the correct way.

    It a very good thing you mentioned the dist. rotor rotation and ....eventually also mentioned these are twin MIE I/B s , not a single engine or I/Os , and that you have Velvet Drives and that the starter apparently has been replaced since it has last started, to see your problem.

    Suggest you check prices for both ARCO Marine and DBElectical starters that fit.
     
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