Some tech questions Mercury T2 ??

[Droll-l6]

Got a Mercury T2 that's going tru a looong term restoration, slow progress at the moment but it's going forward...
Got 99.5 % ft the part's needed but I got some questions..

http://www.drolsum.net/t2rest/images/ak_t2_5.jpg

Planed to use some 2-ring high dome power port pistons from Sierra but after reading a post at this forum some older concerns came up again.

Will the hole in a power port piston come in conflict with the center port on the T2 ?? , will of coarse work but with the lack of some power ? or ?

Tracked down some NOS Merc #9137A13 ( + .015" ) pistons just i case as they might be better performance wise ?.
http://www.boatracingfacts.com/forums/attachment.php?attachmentid=43405&stc=1&d=1311935624


Question #2
Got some NOS reeds for the T2, lately I have spotted some new reeds available for the engine ( CCMS ), would it be a good idea to purchase some new reeds for the engine ?.
Those NOS reeds I got are probably 30 years ++ old , unused but old ...


Arne Kjetil

[baldad45]

Arne the port itself will not be a problem , but the bevel on the piston edge above the port will change the port timing of the center port allowing it to open to soon. Glen :D:)

[Mark75H]

I agree with Glen, but don't think it will be anything you will notice

I don't think there is any problem with the reed material unless it has been left outside

[Droll-l6]

OK about the reeds :) as they are NOS some haven't seen daylight since they were put in the box at the factory, were just looking for an excuse to bye something new for the project;)

As for the pistons, I have already found me some 2-ring NON power port pistons...

http://www.drolsum.net/forum_images/pistons.jpg

From the left...

Mercury 745-6415A2, NOS .015" piston, are going to use these
Wiseco 3009P2 ( D-port MOD ? )
Sierra 18-4510 ( .015" ), I planed to use these pistons...
D.M.I D-7900 ( Persan )

Those other pistons are there just for the opportunity/comparison...

The 6415A2 piston I got here are probably the closest ( to the original ) piston I could find on the marked today ?
2-ring, high dome non power ported piston, square 1/16" thick rings, rectangular rings .

Those pistons were relabeled as 774-9137A13 as this were the number they were superceded to, but the 9137A13 are Half Keystone rings .....the 6415A2 uses rectangular rings.
Can't find any reference to where the 6415A2 piston originally were used ( got Midas ) ...

From the part manuals :

745-5220A1 are the one used in the T2x ( maybe the T2 too ?), STD .
745-5220A12 are the one used in the 650XS, STD.
745-5306A3 are the one used in the 650XS, .015 over.




So for further reference these pistons should work fine in a TII or 650XS ??


6388A3 2-ring highdome without power port STD bore,superceded to 9137A12
8899A3 3-ring highdome without power port STD bore, superceded to 9137A12
5220A2 3-ring highdome without power port STD bore, superceded to 9137A12
.
6415A2 2-ring highdome without power port, .015" over, superceded to 9137A13
9137A13 2-ring highdome without power port, .015" over
5306A2 3-ring highdome without power port, .015" over, superceded to 9137A13
8900A2 3-ring highdome without power port, .015" over, superceded to 9137A13
.
8901A2 3-ring highdome without power port, .030" over, superceded to 9137A14


Beware !!
Some of the non PP pistons might have been superceded to a PP piston, and some non keystone rings might have superceded to half keystone rings, Mercury parts lists can be a bit confusing at times :confused:....

Arne Kjetil

[R Austin]

Not all Mercury Direct charge pistons were created equally. The number after the A on Merc parts indicate a design change. The direct charge pistons in the beginning ran a clearance of .015, skirt to wall. After a few years of very hard starting and poor idleing chararteristics, Mercury just changed the piston O.D. without any notice on both new motors and service parts going forward. Hone cylinder and install a new piston, clearance became .007. Just measure skirts of all NOS parts to know that they are the same size.

[Droll-l6]

Not all Mercury Direct charge pistons were created equally ***.
Have found some reference to an Australian 1150 ( Ausi # 7010763 THRU 7112248 or 1973 > 1978 (http://www.ishopmarine.com/ishop/jsp/AsplIsmCcatViewBase.jsp?&lvlCode=4&pCode=C0002209&path=MM~A0000001~M0000094~M0000097~C0002209&isFromCMS=false&hideAdd2CartButton=&isStandAlone=&is4CmsShop=&reqln=Unknown&reqem=Unknown&reqph=Unknown&reqFor=29&req4Browse=1&docId=&docName=&isForSupStore=true&cCatFilter=MM&eCatSupFldr=supplier-050-025-MM))....

Compared the piston to a new Sierra piston ( only new .015" I got at the moment)..
Diameter at the skirt were identical
Diameter in the ring area were .010" bigger on the Mercury piston ( but they do use different ring designs )...

And the ring locating pins were right above the wrist pin on the Mercury piston, the Sierra piston had a slightly different location ( but could be due the fact it was a 2-ring half keystone ring piston...)

It would have been fun to have ALL the revisions # for THIS type of piston ( and WHY ), but I believe it would be extremely hard to find... got no real use for it ether ;) .

Can only Imagine some of the reasons for changing the number...

Changes in the metal
Design changes ( performance/endurance/easer production )
A change in the subcontractor
Different rings ( type/tolerance ).
Different measurements ( bigger/smaller clearance ++)

I would assume a slightly change in the ally for the locating pin would call for a new # :)


Arne Kjetil