What is 'special' timing procedure for '97 merc 4.3LH?

[jtw]

The sticker on my '97 Mercruiser 4.3LH with Thunderbolt Ignition says: Timing 10 deg BTDC (special procedure required). What is that special procedure? Is it difficult?<br /><br />I'm having some performance issues. Is there an easy way to tell if the timing is off? For example, can I mark the original distributor position, then listen to the effect on idle speed as I turn it a fraction of an inch?

 

[Elk Chaser]

Re: What is 'special' timing procedure for '97 merc 4.3LH?

No point in messing with the distributor unless you are actually setting the timing with a timing light. Moving the dist will change idle speed but not necessarily for the better of the engine.<br /><br />Not sure about the special procedure but I am sure it is something simple such as plugging a vacuum line.....<br /><br />The real question here is what are your performance issues? The timing is usually the last thing that needs to be checked if it has not been messed with.

 

[jtw]

Re: What is 'special' timing procedure for '97 merc 4.3LH?

The perfornance issue is low WOT RPM. The boat has the correct prop. I've already re-done most of the tune-up stuff. The timing was set by the same guys who gapped my spark plugs wrong and who didn't replace the distributor cap and rotor, even though the parts are listed on the receipt.

 

[navigator336]

Re: What is 'special' timing procedure for '97 merc 4.3LH?

Is the distributor a Delco EST one? If so, setting the timing requires a timing shunt which is just a plug that goes into the distributor which when a wire from it is touched to (as I recall) 12+, will freeze the computer module advance and allow you to set the advance to the correct number of degrees BTDC. It's easy, but you need the little shunt plug.

 

[DHPMARINE]

Re: What is 'special' timing procedure for '97 merc 4.3LH?

The engine needs to be put into 'base timing',and it does include a shunt,or wire.Not sure about to 12+ but could be. Some engines get grounded,others need two wires connected,some need something done at the shift interrupter switch.I just pull the manual and check for each engine/ignition/year and follow it.<br />You are welcome to stop by my shop and read it,but I suggest buying your own copy,so you'll have it.Generic manuals may cover this,but the original Mercruiser manual certainly does,at about the same price $30.00.<br />DHP

 

[jlshields]

Re: What is 'special' timing procedure for '97 merc 4.3LH?

jtw, you GROUND to put it in base timing mode. There should be a wire on the stbrd side of the intake manifold with a rubberplug in it. Pull that plug and ground it. There should also be a ground wire close by with a ring terminal on it. Use that. It must be put in base timing mode before you start the engine. I'm with DHP, get the manual. You fry the ECM and you're looking at some big bucks.