merc 25 Powerhead switch...

bnjtown

Cadet
Joined
Jul 1, 2009
Messages
26
hey everyone,

I have a question about what the easiest course of action for a repair is.

I recently purchases a 1999 merc 25 with a blown powerhead (pretty common for that year...) for parts. The motor is essentially brand new condition wise as far as paint, shallow water parts, hood, lower unit.

I also have a 1992 25 that the lower unit is really pitted and banged up. excellent powerhead though. My question is that is it easier to switch the powerhead to the newer much better condition component motor that has electric start or is it better to switch the lower units and electric start components...? This would include swapping the tiller handle to.

I know this sounds a bit dumb but i was given this motor and believe that using my good powerhead in one way or another is probably the way to go. It is off an XD merc and is in my opinion a better and more easily rebuildable (when the time comes) engine, as it does not have to be sleeved to be properly fixed.

Please let me know if this idea seems completely ridiculous.

Thanks for helping
 

Faztbullet

Supreme Mariner
Joined
Mar 2, 2008
Messages
15,937
Re: merc 25 Powerhead switch...

The 1992 if it goes south is junk as its a chrome bore block and would need sleeving where the 1999 is a Mercosil block and can be bored up to .040 oversize...fix the 99 if possible.
 

bnjtown

Cadet
Joined
Jul 1, 2009
Messages
26
Re: merc 25 Powerhead switch...

Are the blocks on the xd motors not factory sleeved?
 

Faztbullet

Supreme Mariner
Joined
Mar 2, 2008
Messages
15,937
Re: merc 25 Powerhead switch...

Nope.. the 88-94 model 18-25hp is a aluminum cylinder with a chrome nickel finish,one scuff or overheat and its time to install a sleeve. The 95 and up use a Mercosil block , a material which is boreable and needs no sleeve but uses a tempered alloy piston and ring(sort of like a B&S tiller engine) and you cant mix and match pistons between the two blocks..
 

bnjtown

Cadet
Joined
Jul 1, 2009
Messages
26
Re: merc 25 Powerhead switch...

ok, got ya. I went ahead and dropped the motor off at the engine shop today. Hoping all it needs is maybe a set of rings as when we pulled it apart there was not scuffing or burn marks. Motor set for a while without being run so maybe one was just stuck.. Will know more about it tomorrow.
 

bnjtown

Cadet
Joined
Jul 1, 2009
Messages
26
Re: merc 25 Powerhead switch...

also does anyone know where to find a good service manual for these motors? i would like to find a factory one but im having a little trouble running one down in the little looking i have done. So far all i have seen are manuals covering 20 - 75 or larger. It seems they would sacrifice some detail on 25's in order to cover all these motors
 
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