Help with 25 HP Short Shaft 2 stroke

OldMercsRule · Oct 15, 2008

Hi folks I have a 25 Merc 2 cylinder 2 stroke engine Serial number 08223063

#1 What year is this engine?

#2 I lost the lower cylinder, (spark) and I swapped the wires from the switch box (Merc Part # 339-7452A7) to verify both coils fire and both plugs fire which leads me to the spendy switch box, (I think).

Arggggggg!!

If one cylinder has no fire and the plug wire, coil and plug works (from the signal for the top cylinder) is it the switch box (as I think it is) or could it be something else?

Thanks for the help. JR

DutchMerc · Oct 15, 2008

Re: Help with 25 HP Short Shaft 2 stroke

I think you've already guest the answer... You are looking for a new switchbox now. Since the type you have is probably the type with the srewed-on connections, you might have to replace some wire's also...The newer type has fixed wire connexions, but is fully compatible.

OldMercsRule · Oct 15, 2008

Re: Help with 25 HP Short Shaft 2 stroke

Thanks do you know the year? USA model. JR

OldMercsRule · Oct 16, 2008

Re: Help with 25 HP Short Shaft 2 stroke

Bump.

I have looked every where to attempt to find out the year of this engine.

I think it is a US engine but I really don't know that for sure as I bought it used two years ago in the Seattle area.

The serial number is 08223063 on the engine bracket. I saw (somewhere) that Auzzie #s may have been up there in that range.

There is a date that was hard to read on the engine (or a part on the engine), that looked like 6/1981.

The switch box (that looked origional) was 339-7452A7 and I found a Sierra switch box with the older style wires (instead of the nuts) part number SIE18-5777 that supposidly replaces 339-7452A15, A19. (doesen't mention 339-7952A7).

How can I find out what year this thing is?

I have searched all the obviuos places on the net.

Thanks in advance to anyone willin' ta help me. JR

Sea Rider · Oct 16, 2008

Re: Help with 25 HP Short Shaft 2 stroke

[QUOTE
How can I find out what year this thing is?

I have searched all the obviuos places on the net.

Thanks in advance to anyone willin' ta help me. JR[/COLOR][/QUOTE]
...................................................................

The year is relative as they don't vary much/anythig in years...

Is your engine like this, pi?on/shaft tiller ?

santeelooking · Oct 16, 2008

Re: Help with 25 HP Short Shaft 2 stroke

call a boat motor repair shop they have books with all the serial numbers and can tell you the year just by looking in their books

santeelooking · Oct 16, 2008

Re: Help with 25 HP Short Shaft 2 stroke

call a boat motor repair shop they have books with all the serial numbers and can tell you the year

Laddies · Oct 17, 2008

Re: Help with 25 HP Short Shaft 2 stroke

OMR, I think your number starts with OB no 08 and thats why you can't find the year so that would make it a 1988.

OldMercsRule · Oct 17, 2008

Re: Help with 25 HP Short Shaft 2 stroke

Sea Rider said:
[QUOTE
How can I find out what year this thing is?

I have searched all the obviuos places on the net.

Thanks in advance to anyone willin' ta help me. JR[/COLOR]

...................................................................

The year is relative as they don't vary much/anythig in years...

Is your engine like this, pi?on/shaft tiller ?[/QUOTE]

Thanks for the pics.

No that one looks newer then mine. This engine is tiller with the shift in the tiller. (I bit hard to get used to fer an old Johnyrude fan). That is a dangerous feature of black boat anchors, that I'm finally used to now. Easy to swamp a boat if ya only have one functional brain cell that learns old habits n' resists new tricks, (haven't swamped it yet).

I have two other 25 HP Merc 2 cly 2 stroke short shafts that run perfect.

A 1989 Canadian one that looks similar and acts similar to this one (except the round choke prime), and a 1996 that looks a bit different, (Cowling), but acts very similar to the other two engines as well.

Both of the other 25(s) have a round choke knob that ya twist clockwise to increase engine speed fer a cold start and pull out fer a raw fuel prime which makes them start very easy in cold weather.

This one has a square choke knob that pulls out with two positions one fer slightly faster idle, (still slow cornpared to the other two engines), and farther out fer choke.

In fact the fast idle is nowhere near as easy as the two later model engines. Which leads to harder cold starts.

Once started, it ran very good prior to the one cylinder losing the fire.

When I changed plugs I found that the previous owner has installed surface gap plugs which I replaced with the cornventional NGK plugs the other two 25s use. Hope that didn't blow up me switch box.

That is why I'm tryin' ta find the actual year of this engine so I can verify the standard plugs are what is used before I install the new switch box n' potentially blow it up again.

I know the 1996 uses the bolt type switch box, not sure about the 1989 yet; which I plan to look at when I get back up to the lake.

Thanks again!

OldMercsRule · Oct 17, 2008

Re: Help with 25 HP Short Shaft 2 stroke

Laddies said:
OMR, I think your number starts with OB no 08 and thats why you can't find the year so that would make it a 1988.

Purdy sure it is 08 not OB: Bob, as I was aware of the alpha neumeric carp Mercury did ta trick ol' farts like me. I will look again much closer with a maginfyin' glass when I get up there again ta double check.

I also am purdy sure of the 6/2/1981 date on a part (or the engine itself).

Hard to know if that is origional date from something from the factory, but me bet is: it is!!!

I note that the previous owner discornnected the red button kill switch in the center of the tiller handle to the switch box.

I have not yet verified that kill switch is bad, but I will.

The other toggle kill switch is on the starboard side of the powerhead and werks fine, (instead of at the base of the power head), as the two newer engines are.

Thanks fer yer help. JR

OldMercsRule · Oct 18, 2008

Re: Help with 25 HP Short Shaft 2 stroke

Sorry ta bug you fellers with me problems here.

I think I solved the spark plug question.

Looks like the late 1970s n' earlier 20 HP Mercs used a surface gap plug, and every Merc 25 from 1980 on (which seems to be when they were introduced) uses the NGK BP8H-N-10 @.040 gap which is what I put in the beast prior to the switch box blowin' up.

The NGK site helped sort this out fer me.

I think the plug issue is now solved and the prior owner may have used 20 HP surface gap plugs, (which did werk fine), prior to me changin' plugs. (I guess if it ain't broke don't mess with it, eh)?

Anybody here own a 1980-1987 25 HP Merc, (or have real specific knowledge of em)?

#1 Is the choke control ya pull out square?

#2 Is the second of the two kill switches, (the first one is in the center of the end of the tiller), on the starboard side of the power head?

How do you increase the idle engine speed at cold start?

(My 1989 and 1996 25 HP choke corntrol is round and twists ta increase idle speed, and the second kill switch is in the center facing the boat at the base of the power head).

Thanks in advance to any owner of this vintage engine who cares to help me sort this out. JR

Help with 25 HP Short Shaft 2 stroke

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