some questions regarding an old merc 3.0

[Lars0ne]

Hey hello.
i'm new to this forum, i've tried to search, but did not find what i was looking for.
since i'm from sweden i hope u guys will accept some miss spelling and grammar faults.

last summer i bought an old boat with a merc 3.0 or atleast i think it is. Serial 4481451.
i have : 2blocks 1head 2 carbs 2 mainfolds one stainless 3sets of headbolts 2 waterpumps and so on.
i found that i have one valvecover to 120hp merc and one 140hp but only one cylinder head.
for your information both blocks have the same castnumber. Is there any way to tell if the cylinder head fits a 120 or 140 merc?

the engines was stripped to bare blocks and put i boxes along with all the other parts. i've orderd all gaskets and rebuild kits i could find for the 3.0 engine so i hope it is a 3.0 hehe. i will try to make a semi serious rebuild of the engine since it will cost me a fortune to make a complete rebuild. since it's not that long boating season here in sweden and mainly fresh water (non salty) the engine is hopfully not that worn.

im looking for all info that i can find on stuff that is different the 2 engines apart.

since we have metric bolts in swe i'm wondering on difference on UNC and UNF standards aswell. i know google is a good way but i've put alot of effort to register and writing this so i might aswell ask here.



Lars from Sweden

 

[Don S]

Re: some questions regarding an old merc 3.0

Here is the OEM service manual for those engines. There are specs on all the engine parts in section 8 of the manual.
http://www.4shared.com/document/3AHpVLYw/Service_Manual_02.html

 

[Bondo]

Re: some questions regarding an old merc 3.0

Is there any way to tell if the cylinder head fits a 120 or 140 merc?

Ayuh,.... The difference in blocks is the diameter of their Bores,....

The heads don't care, 'n will fit either motor...

 

[Lars0ne]

Re: some questions regarding an old merc 3.0

Ayuh,.... The difference in blocks is the diameter of their Bores,....

The heads don't care, 'n will fit either motor...

thats the kind of answer im looking for. simple and clean.

no difference in valve size or carb? both using the rochester?

you wont get rid of me now.. got tons of beginner questions about this engine.


Thanks
Lars

 

[achris]

Re: some questions regarding an old merc 3.0

...since we have metric bolts in swe i'm wondering on difference on UNC and UNF standards aswell. ...

UNC = Unified National Coarse, UNF = Unified National Fine

As far as naming the thread form, metric uses the pitch of the thread and imperial (UNC and UNF) uses TPI (Threads per inch)..
So with a metric thread the pitch is the distance between each thread, the higher the number the coarser the thread.
With imperial it's the opposite, the higher the number the finer the thread. The number is how many threads per inch (1 inch = 25.4mm)
Another major difference is that unified bolts (and nuts) are in 1/16" (about 1.6 mm) steps, usually starting at 3/16".

As an example, a 1/4-20 is UNC, 1/4-28 is UNF. That means the bolt is approximately 6mm with a thread pitch of 1.27 (UNC) or 0.907 (UNF).

Unfortunately for you metric and imperial nuts and bolts are not interchangeable, so you are going to need to learn a whole new system. UNC and UNF are the USA system for nuts and bolts, the UK also has their own system, BSW and BSF, and we haven't even begun on pipe-threads yet

I have a pocket book that I have scanned to PDF that has all this information, and lots more. If you'd like a copy, pop me a Private Message (PM)..

Chris.........

 

[Lars0ne]

Re: some questions regarding an old merc 3.0

haha thanks Chris.
why are you so stubborn bout inches, makes no sens!

 

[achris]

Re: some questions regarding an old merc 3.0

haha thanks Chris.
why are you so stubborn bout inches, makes no sens!

I'm not being stubborn about inches, I'm happy with either metric or imperial. But if you're working with imperial systems you absolutely must talk inches. Most imperial bolt sizes do NOT have an exact metric equivalent, and none of the thread pitch do...