Timing and fuel for 1976 Mercury 1500

[powertower]

For about 20 years or so I had the timing set on my 1976 Mercury 1500 at 30 degrees advance and ran premium fuel, premium oil, octane boost and lead supplement. The motor ran very strong with no apparent problems. Last season the water pump starts to seem weak so I take it to a local marine shop to get it replaced and decide to get the carbs rebuilt and a tune-up at the same time because I have not done anything but change plugs for 20 years. They set the timing to 21 degrees and give me a lecture on only using regular octane fuel, no octane boost, etc.. First of all I hate being talked to like I am stupid and second the motor runs like crap. Big bog on the hole-shot and less top end. I go back to the shop and want the timing restored to 30 degrees but they won't go beyond 21 degrees so I contact 3 more shops with the same line "21 degrees is what the manual recommends and we will not set any higher because of liabilities, etc., etc., we don't work on motors that old, etc., etc.." Now I am really pissed off - I take in a boat running perfectly well and now it is a piece of ****. I finally find a small shop just starting out and have them dyno the motor. Surprise, surprise - the timing is now adjusted to 27 degrees and the carbs are re-adjusted to lean them out a bit. I just had the work done and have not had a chance to run the boat yet but when I do it will still be premium fuel with octane boost and lead supplement. I bet it runs a heck of a lot better than at 21 degrees. Come on, the motor is a 1976 and does not owe me anything - I don't care about extending the life, I just want it to run as it was meant to - strong hole shot and 50+ mph on the top end.<br /><br />Any comments or suggestions?

 

[mellowyellow]

Re: Timing and fuel for 1976 Mercury 1500

welcome aboard mate,<br />wrenches in question r doing what MERCURY has told<br />them to do... MY 71 115 tower ran like a scalded<br />dog with 87 octance and no additives... coincedence maybe?<br />good luck,<br />M.Y.

 

[powertower]

Re: Timing and fuel for 1976 Mercury 1500

If the timing change and carb adjustment solved the problem I will try running on 87 octane with no additives. If I don't need them then I won't use them. I just assumed they were doin me some good.

 

[sorrydog]

Re: Timing and fuel for 1976 Mercury 1500

Those originally had a max timing of 23. A merc service bulleton later said to use 21. Use 87 at your own and your #3 piston's risk. Same for advanced timing.<br />I think in the racing days of that motor they would run high octane fuels with that much timing, but I don't know because I wasn't around back then.<br />Did the shop check your flywheel timing marks? <br />I'm surprised it had lived- is your boat really light?

 

[hohnstadt]

Re: Timing and fuel for 1976 Mercury 1500

Sorrydog - your last comment intrigues me because I just bought a '69 merc 500 and turns out its #3 piston is fried (other 3 look fine). What does 87 octane have to do with the #3 piston?

 

[ZmOz]

Re: Timing and fuel for 1976 Mercury 1500

You shouldn't run 87 octane in these motors with 10 degrees timing. If you run 87 on 27 degrees, you're almost guaranteed to need a new $1000 powerhead. If you think about it, for a full tank of gas the difference between premium and regular is only a couple dollars.