Logo
FULL SITE MENU

Dating a mariner

D

Dingus

New member
Not what you think....I have looked at the tables and I am not 100% certain I know what year and country my Mariner 25 was made in.

serial number is 6634733

tag does Not say made in Japan

color is matching gray on lower and upper with multicolor stripes under the Mariner name, mostly shades of orange

I think it is a Belgium made 1985, maybe a 25M, not sure of the sub model designation.

Just bought it used, it has sat for a couple of years. I have not fired it up yet.
 
Not made in Belgium - Belgian serials start with 9, 7 for Canadian and 8 for Australian.

That was a US built Mercury Mariner, almost certainly a "25 XD" in the Mariner flavour (which may have been called a Marathon model) built late in 1985. More than likely one of the last to run off the presses before they started building the "new" 86 models which carried the alphanumeric production (serial) number - 0A1xxxxxx etc.

1985 models very often do not show up in the standard serial charts. Some had the old style production numbers and some the new - neither of which were charted very well.

Irrelevant in this case - treat it as an 85 or an 86 when looking for parts. They were identical in any event...
 
Seeing different info for plugs, Seloc manual has different for 85 vs 86 both different than PO had installed. What do you suggest?
 
From factory these shipped with an L76V surface gap Champion however, Champions did not take full advantage of the power of the ignition system on these motors (and surface gaps tend to work their best on warm engines running at higher rpms - so not particularly suited for the "portable" (25 horse and under) line).

In the later 80's Merc changed the recommendation on these to a "gapped" NGK BP8H-N-10 gapped at .040" (which is what I would personally run).

If you wish to run the surface gap plugs I would still make the switch from Champion to NGK. An NGK BUHW would be the equivalent of the Champion L76V.

Why not Champion?

Champions were originally designed to run on OMC ignitions which only put out about 75% of the power you get from a Merc Thunderbolt 4 ignition. Merc's originally fired Autolite sparkplugs (which lost so much market share to Champion that Merc had to make the switch for a few years to get what they needed for their new motors). The resistance on the Champions is better suited to the 50'ish thousand volts you get from the (weaker) ignition. The NGK's like the (almost) 80,000 volts that the T4 ignition kicks out so you get better cold weather/cold start and idle performance from them (but to be fair, both run fine on a warm engine at higher rpms).
 
Back
Top