TIMING A V-6 MERCURY
by Dave Raymoure

 

This article generally paraphrases the Mercury Manual on timing 2.4 and 2.5 V-6 motors. The adjustment is the same for carbureted or EFI motors. The intent is to explain the adjustment procedure used to set the maximum and primary pickup timing. You may need to modify the timing values used as examples based on your motors specific timing requirements.

There can be some differences between motors with stock flywheels and those with lightweight fly wheels. Degree markings are not always present on the lightweight ones. My stock steel flywheel has markings in one-degree increments around the specified settings – my light one has no markings at all. If your flywheel does not have the specified timing marks you need, at idle or maximum timing, it is possible to determine the location and mark the flywheel. You need to measure the circumference of the flywheel in inches, and divide by 360. This will give you the distance in inches on the circumference of the flywheel that is equal to 1 degree of timing. Using the TDC mark, and the 25 degree mark discussed below, you can add or subtract the distance needed to mark your specific degree location.

For this example we’re going to assume your max timing spec is 25 BTDC, primary pickup spec is 8 degrees ATDC, and that you do not have a timing advance module. If you have a timing advance module it must be disconnected prior to timing, and your max. timing value will be less than 25 degrees. You will need to check the specification for your particular motor for the correct timing values.

The only tools you will need are open-end wrenches, a Phillips screwdriver, and a timing light. You will also need an adaptor that will screw into a sparkplug hole and a dial indicator with an actuating rod long enough to extend through the adaptor and pick up the piston movement. The photograph below is an example of one machined from a bar of aluminum.

  

Make sure the trigger link rod adjustment is correct. It should be 11/16 (.688") from the CENTER of the rod before the bend, to the contact face of the locking nut.

 

If you have the timing slide pointer on the flywheel cover, loosen the two screws so it will slide left and right.

If you do not have a pointer, make one from a piece of wire and attach it to any bolt or bracket available. The pointer must point to the edge of the flywheel so it can be aligned with marks on the flywheel, and be stiff and secured well enough so it won’t move while the motor is cranked.

Remove all sparkplugs so you can turn the flywheel by hand. I ground all plugs also just to make sure the switch boxes do not get damaged.

Insert the dial indicator and threaded adaptor into cylinder #1 sparkplug hole.

Turn the flywheel clockwise until the dial indicator indicates top dead center. Turn the flywheel slightly back and forth to verify TDC. There will be a "dead spot" where some flywheel movement will not result in movement of the dial indicator. I use the center of this area as TDC.

If you have TDC ( 0 degrees) indicated on the flywheel, adjust the pointer to align with this mark. If TDC is not marked on the flywheel, make a mark on the flywheel and align the pointer with the mark. White paint works well, so does white correction fluid or a fine paint pen. Just make sure the mark is as thin as possible, and will be visible in the flash from a timing light. This is the place to be creative. I’ve used white paint that makes too wide a mark and gone back with a black fine point sharpie marker and narrowed the line. Whatever works for you. Some people use a punch and hammer, but personally, I would be concerned about even a light impact load to the crank and upper bearing.

Tighten the timing pointer slide screws, if applicable. Continue turning the flywheel clockwise until the pointer points to 8 degrees AFTC. Mark the flywheel at this location also. Remember, if your flywheel is not marked you will need to calculate the distance on the circumference that equals 8 degrees and use that distance from TDC to mark the flywheel.

Turn the flywheel counter clockwise PAST .150" before top dead center – maybe .200"to .250" or so. Carefully turn the flywheel clockwise again and stop at .150"BTDC. This removes any slop and insures the piston is approaching TDC from the same direction as in normal operation. .150" BTDC is equal to 25 degrees BTDC.

If there are degree markings on your flywheel the indicator should be pointing at 25 degrees. If you have a 25 degree mark and the pointer is close, but not aligned, adjust the pointer so it does align. If there no markings, put another mark on the flywheel aligned with the pointer. This will be the maximum spark advance timing mark. It’s best to make this mark unique from the marks at TDC and 8 degree ATDC.

Make sure the battery is fully charged.

Remove the dial indicator and adaptor, and install the spark plug in cylinder #1. Leave the other plugs out so the motor will spin at a higher cranking rpm.

Hook up timing light to cylinder #1

Disconnect the throttle cable from the throttle control lever.

If you’re using a remote starter, one connecter goes to the small solenoid post with the yellow wire with red tracer. The second connecter goes to the large terminal with the heavy red cable from the battery. If you are not using a remote starter, you’ll need a second person to turn the key while you open the throttle and hold the timing light.

 

SETTING MAXIMUM TIMING

Loosen the lock nut on the maximum spark advance screw.

Turn the motor over while holding the throttle control lever at wide-open position so the maximum spark advance screw is against its stop. With the timing light, the pointer should align with the 25 degree (.150") BTDC mark on the flywheel. If it does not, screw the maximum spark advance screw in or out until the pointer is aligned with the mark while cranking.

Tighten the lock nut on the maximum spark advance screw.

 

 

SETTING IDLE TIMING

Loosen the lock nut on the primary pickup screw

Turn the motor over while holding the throttle control lever closed so that the idle stop screw is against its stop. The pointer should align with 8 degree ATDC mark on the flywheel. If it is not, adjust the primary pickup screw in or out until the pointer aligns with the 8 degree ATDC mark while cranking.

Tighten the locknut on the primary pickup screw.

 
 

This section features articles written by you guys.  Submit whatever you would like - as long as it applies to HydroStreams, motors, trailers, or towing vehicles.  Please send it to me in a form where I can just insert it into this page (some kind of Word processing document would be good).  It would be a good idea to check with me first to make sure nobody else is working on the same topic.  Everyone please consider writing an article and sharing some information that will help out your fellow Streamers.

 


[ Home l About I.H.R. l History l Models l Registry l Members' Pictures l Feature Article l Tech Talk ]
[ Literature l Events l Top Guns l Guest Boat l Classifieds l Video Gallery l Racing Corner ]
[ Prop Slippage Program l Animated Videos l Screen Savers l HIN Decoder l Links l Contact Mark ]