470 timing question

[fmalott]

I going to tackle the timing today on my 1983 470 quick question the manual says 4 degrees BTDC but i converted to electronic ign. does the degrees stay the same for elec. ign.?

 

[Don S]

Re: 470 timing question

Yes, same timing. 4? BTDC @ idle rpm.

 

[fmalott]

Re: 470 timing question

THANKS Don S

 

[fmalott]

Re: 470 timing question

Finally got back to the boat not enough time in a day! i was reading the manual some more and i followed the instruction for checking the timing chain play all's good they say replace if an 1" or more play my chain measured 1/2". now for lining things up for TDC i lined up the markings and i'm going to use a straight edge to line up properly. Now the question i could not see the info in the manual, when you straight edge the marks is there no tension on the chain or is there tension on one side. i'm thinking the motor turns CW so should you have tension on the opposite side of tensioner for TDC

 

[stonyloam]

Re: 470 timing question

You should set the timing with the engine running, so static timing is just a guess anyway.

 

[fmalott]

Re: 470 timing question

got the motor running so far so good no leaks. got the timing set but at 4 degrees like the manual said it ran like crap hard to start adjusted idle mixture screws the 2 bbl had two of them with no luck still ran like crap BUT still ran. i turn the distributer until it was at 10 degrees and it ran and idled perfect i gave it a little throttle and there was no pinging being advanced. Now this test was done on the muffs i'm ready to test out on the water will i hear the pinging then being under load. What do you guys think?

 

[wrestling coach]

Re: 470 timing question

I have the same year and model as you. I converted to a Pertronix I system. Module, coil and wires. I went to NGK plugs and gapped them at .040". I inspected cleaned and lubricated the advance weights and springs in my distributor. After reading many posts about electronic conversions I set my timing at 6*BTDC. Mine idles smooth and runs strong. I think 10*BTDC is too far. I would be afraid of detonation. That can wipe out pistons over time. JMHO.

Dennis

 

[nola mike]

Re: 470 timing question

Merc changed their recs for timing on these engines--originally it was 8' BTDC. They went to 4, presumably fearing detonation. I'd certainly be hesitant to advance it to 10. And if it isn't running at 4', you have something else wrong. BTW, with the electronic ignition you're still getting the same firing "spacing" as with the points, so nothing changes there. Rotating the distributor just changes when the firing occurs (same as with points).

 

[ctriverhouse]

Re: 470 timing question

Initial Timing Specification
Change For All 3.7 Litre
(224 CID) Engines
The quality of todays fuels have changed considerably
over the last 5-10 years. Because of this, the 3.7
Litre and 3.7 LX Litre MerCruiser engine timing will be
set (by the factory) at 4 degree BTDC. The timing
specification will be unnoticeable in performance for
all practical purposes and allowing for more tolerance
to todays fuels.
It is suggested that when a dealer services one of the
following engines, the ignition timing be reset to 4 degree
BTDC instead of the original 8 degree BTDC. All
service manuals will be changed in the future to reflect
this timing change.
MIE 470
MCM 470
MCM 485
MCM 488
MCM 165
MCM 170
MCM 180
MCM 190
MCM 3.7 Litre
MCM 3.7 LX Litre

From 1987 service bulletin