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  1. #1
    Seaman Apprentice
    Join Date
    May 2008

    Default how to properly check timing on 97 merc 5.7

    97 mercruiser 5.7
    i have a overheat problem and i was gonna check the timing on it cause ive went thru most other options...
    How do i do it? i have never done it before. what kind of timing light should i purchase does it need to have timing and advanced timing ?

  2. #2
    Fleet Admiral HT32BSX115's Avatar
    Join Date
    Dec 2005

    Default Re: how to properly check timing on 97 merc 5.7


    You just need a "regular" timing light. but I would also start with another known gage to verify that you really are overheating...

    If it's a 97 it's probably a Thunderbolt V ignition system?

    It will have to be put in "BASE" mode before you check the timing.

    You set the timing at idle rpm 10* BTDC while in the base mode. The service manual indicates how to put it in base mode.

    Here's the specs.

    There should be a wire hanging off your distributor. It's PUR/WHT in color. It may have a little rubber or plastic plug in the end to insulate the connector when not being used.

    You ground it which places the ignition into "Base Timing Mode" Then set the timing the "normal" way. You can also adjust the carb idle mixture and idle rpm too.

    Don't forget to lift the wire from ground after you're done.

    The service manual outlines the procedure. Evidently that service manual is not on Boatfix. If you don't have one it would be a good investment if you're planning to do your own work or you want to know what's going on when someone else does it.

    Now having said all that, timing is not frequently the cause of overheats in a boat engine. You might want to check the raw pump, and raw water system for debris from a previous raw water pump disintegration or other source and the pump itself for problems. Also check for good water thru the manifolds/risers, thermostat, and circ pump etc.

    Maybe you checked all that stuff...


    73 de Rick
    I use xxx oil and have never had a problem........
    1987 FourWinns 211 Liberator, 7.4L- Bravo III installed by ME,
    Formerly OMG 460 King Kobra powered
    1947 Stinson 108-2 Station Wagon
    , Franklin 6A-335B. Hartzell CS 2-blade prop
    All PM's cheerfully answered! Please ask tech questions in the appropriate forum so everyone's included

  3. #3
    Honorary Moderator Emeritus Don S's Avatar
    Join Date
    Aug 2004
    Western WA.

    Default Re: how to properly check timing on 97 merc 5.7

    Nothing in that tech manual for the TB5 Rick. In the real world, I always liked those tech manuals. All the good info, without all the step-by-step procedures.
    Below is the link to the OEM #17 manual for your engine. Look at page 4B-19 for timing and carb adjustment procedures.
    Don S.

    Please, no PM's (Private Messages) regarding boat/engine problems.
    That is what the forums are for.
    Only forum/moderator issues will be answered in PM's.

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