Question for the Merc anoraks

9D280 · 11 June 2009, 12:40

Your starter for 10:

I have a clamshell with a late 80s / early 90s set of decals on the lid.

Having dismantled a sizeable chunk of it, what I find hints that it's an early 80s "650" machine, and based on a few trawls round Ishop's microfiches, (They are American, so may not match what we were buying in Europe back then) I reckon the engine could fall into one of three serial number ranges (the original ID has long gone).

4382057 THRU 4571651
7073473 THRU 7087822
9112989 THRU 9135824

Having compared a good chunk of the powerhead & major components of the leg & gearbox, I cannot find any differences in part numbers for the major components.

So, the question - are these three series of numbers all for the same engine, but with different decals? or were there more subtle changes that triggered the number series change? - or was it just a different Model year?

If there were subtle changes, what were they - I'd like to make sure this rebuild has all the changes Merc made for maximum reliability!

Nos4r2 · 11 June 2009, 13:03

Pass.

You need to take a trip to Iboats and ask one of the merc engineers there if Turbodiesel doesn't know.

chewy · 11 June 2009, 13:19

Mines a 60 clamshell, serial number 9416020

Turbodiesel · 11 June 2009, 13:29

Without going through all the part numbers! They will be very similar between all those serial numbers. Sometimes you find that the engines built in the US have different spark plugs or something weird like that. The Powerheads gearboxes and major components will be the same. They do running chages quite oftern so the serial number breaks could just be for those. But without looking at all the part numbers its hard to say what the changes are.

9D280 · 11 June 2009, 13:36

Chewy,
It's one of them but with red instead of brown stripes. I have it in m head that the brown came before the red stripes.... But then I also have to assume that my case is original and not a replacement for one that went swimming or was broken by a gust of wind when being removed.....

Turbo,
Yeah., that's what I started on, and as you say none of the major components seem to differ. I was kind of hoping some knowledgable person might be able to save me a couple of long boring evenings with the "minor" components......

uncle al · 11 June 2009, 14:04

when you set up these clamshell 60hp you need to be carefull because if you dont you can cause detonation basically W.O.T=19 degrees BTDC, fuel/water preassures as per the service manual and prop the obm for 5,800rpm@W.O.T

9D280 · 11 June 2009, 14:14

Al,

Thanks. I am aware of the detonation issues with these engines, I had heard 15 BTDC is a good place to aim for to guarantee no devastation - 19 is presumably the edge of the proverbail cliff?

Water pressure - when I got it the plastic outlet fitting was missing. Needless to say one of them is on my shopping list! Any idea what the story is with the later "no thermostat" ones? Was that a reliability improvement? (is it worth me looking for a replacememnt cover to suit & ditching the 'stat?)

uncle al · 11 June 2009, 14:21

set WOT 19 btdc ! NOT 15 @WOTwe have not heard of any problems at that setting there was a castting problem i think it was the earlier obms but i am not sure it was a long time ago thermostat
again i cannot remember.
to be flippant why not buy some chain and just use it as an anchor?

9D280 · 11 June 2009, 14:35

OK, thanks. I can't remember where I heard / read that.....

Anchor? where's the fun in that?

Main reason (apart form the rebuild entertainment) is that it's a super light 60 (only 5Kg heavier than my Suz 30!) and with a boat of a similar vintage & a 110KG transom limit.....

uncle al · 12 June 2009, 13:41

the fun in converting it to an anchor is the big splash when it goes overboard ,as you may have guessed it is not my favourite obm

9D280 · 15 June 2009, 10:29

Yeah, they do seem to have a bit of a "marmite" effect on people!

On the plus side, they are a marvel of weight reduction & compactness. On the down side, those very features make them a pain in the **** to get at anything to service it! I also can't believe how "random" the fasteners are - Both my Japanese machines I could service with a couple of sockets and a crosshead screwdriver. This Merc I needed 3 sockets and a spanner just to drop the gearbox, and don't start me on the epic of getting the carbs out......

Right now, the weight (or lack of same) is the reason I am keeping it going. Hopefully I won't be under the lid too often once it's back together!