1968 Mercury 1250ss pistons

[TomSawyer]

I am trying to find 2 good used pistons to fit the motor mentioned above. Serial # 2397885. I have called all the salvage yards on the sticky in this forum, no luck. I have tried oldmercs.com and a new one without rings is $250. I am hoping someone in Iboat land has some they can part with. Also what years/models used these pistons? Thanks in advance.

 

[194269]

Re: 1968 Mercury 1250ss pistons

That piston is used only in the '68 &'69 1250's, have you tried some of the after market suppliers such as Seria (NAPA stores).

 

[TomSawyer]

Re: 1968 Mercury 1250ss pistons

Thanks for the advice. I tried Napa, no luck.

 

[Faztbullet]

Re: 1968 Mercury 1250ss pistons

To my knowledge no one makes a "aftermarket" piston for this engine....

 

[cbone]

Re: 1968 Mercury 1250ss pistons

It makes me wonder if pistons from the 1969 125 mercs or 1970 115 mercs would work. the 1968 piston was the only year they made it, which tells me there were likely problems with them, why else would Merc reengineer a piston for the sake of 1 yr. They went from a convex high rise to a concave high rise. I can't believe they reengineered the block as well and I believe the 115 block is identical. Also of note is they changed the timing from 34 btdc to 23 btdc between the 1968/69 125 and the 1970 115 merc which is is a 30% adjustment, very significant, makes me wonder if this was because of detonation problems on the 125. I have read in forums that on the 115 merc there was even recommendations to go to 20 btdc because of the changes in gas octane.

 

[Faztbullet]

Re: 1968 Mercury 1250ss pistons

There was no problems as the engineering changed. The blocks went to a "direct charge' design. This feature is on the transfer side of the engine starting with the C-shaped piston deflector, shape of transfer ports, dividers/splitters on/in the transfer covers/channels. The Direct Charge system was produced on the Merc800 in 1969 and later model inlines. (1970 1350/1150 engines)

 

[cbone]

Re: 1968 Mercury 1250ss pistons

Does that explain why they changed the piston design on the 125 between 1968 and 1969? Was direct charge introduced on the 1969 1250? It makes no sense for profit reasons to make changes for the sake of change if everything is good for the sake of a model year. Why wouldn't they just wait till 1970 when the 125 merc became the 115 merc. Who knows.

 

[Faztbullet]

Re: 1968 Mercury 1250ss pistons

It makes no sense for profit reasons to make changes for the sake of change if everything is good for the sake of a model year.

It was changed as due to the fact the engine had better low end punch,more hp could be made and better fuel mileage plus they tore the Johnrudes up.(more sales!!!!)

 

[194269]

Re: 1968 Mercury 1250ss pistons

There is no difference between the production 68" and 69" 1250 piston design, it was a two year model and a very good engine. Maybe you are thinking of the 1250 BP which was a racing engine and did use the Direct charge design. The only production 1969 Direct charge engine was the Merc 800, a four cylinder. The 1969 1250 and the 1970 115/135 use different blocks, very little is interchangeable between the two.

 

[cbone]

Re: 1968 Mercury 1250ss pistons

I was basing the piston change assumption on the online parts manual, they are different part numbers between 69/69 on the 125. 3512A vs 3560A-6.
Ya I guess it makes sense to go to direct charge if it will sell more motors, my 68 was always pretty good out of the hole though.

Question, what could cause water to be behind the fuel pump between 3 & 4. I mean I took it off a couple years ago and there
was water in the larger fuel pump hole. I put all new gaskets in the head but it always seemed like number 3 was running wet, and missing, steam cleaned. Swapped plugs problem stayed with 3. Coincidentally it was that piston that had a compression of 30 and the rings were ceased which is why I am here. I have the block disassembled, can't see any cracks anywhere and filled it with water to see if there were any visible leaks, none. Maybe I need to retorque the rear head bolts. Engine seemed to have a milky mixture coming out the exhaust like water and oil mixing. The block also had one stripped mounting bolt (the ones that mount the block to the base) from the rear, back left second bolt in. That particular bolt hole has very little female thread, I have had that heli coiled and the bolt is back in. Comments?

 

[cbone]

Re: 1968 Mercury 1250ss pistons

I'm sorry guys, I just had a thought, I might be hijacking this thread, should I start another? And Tom Sawyer, I have found 2 new ones, they want 200 a piece, I talked em down to 150. I have also found a guy that says he has some used ones at 50 a piece. I'm going the used route first with 6 sets of rings. Once I have mine I will let you know my contacts if you still haven't found any. I have been scouring the net for a month to find them, scarce as hens teeth.

 

[TomSawyer]

Re: 1968 Mercury 1250ss pistons

I'm sorry guys, I just had a thought, I might be hijacking this thread, should I start another? And Tom Sawyer, I have found 2 new ones, they want 200 a piece, I talked em down to 150. I have also found a guy that says he has some used ones at 50 a piece. I'm going the used route first with 6 sets of rings. Once I have mine I will let you know my contacts if you still haven't found any. I have been scouring the net for a month to find them, scarce as hens teeth.

Thanks I found some here locally. 50 bucks each. I guess I got lucky.

 

[cbone]

Re: 1968 Mercury 1250ss pistons

Thanks I found some here locally. 50 bucks each. I guess I got lucky.

Mine were $60 with rods attached