Merc. V8 305 Identification Help

[eztiger12]

Hi,

New to this site, but it's been of great help so far.
To make a long story short, I'm new to the boating world but off to a bad start. I bought a boat with a cracked block.

I'm now trying to identify the exact model, year and pedigree of the block so I can rebuild it and shop for a new block.

This is the information I have in hand:

The boat is a 2355 Bayliner 1995
Mercruiser v-8, 305, 5.0 L engine.
With an Alpha 1 out drive

Owner manual says the serial number of the engine is: H 4-50B100HS
0F418744

This is the exact way it's written on the manual.

I found an Id plate on the engine (Rear sbd side) with F418744.
Block is stamped on the middle of sbd side with the #627.
Block is stamped in the front with the #638
Block is stamped at the rear of the port side with #5L SGI.

I cannot find anything that matches up at 100% to perfectly Identify the engine in order to find another block.

I've gone through this site as well as many others........
Please do help.....I'm loosing hope....
Thanks in advance to anyone that replies......

 

[Bondo]

Re: Merc. V8 305 Identification Help

0F418744

The Merc erial # says it's the original motor......... A 1988 to 1995 305 Chevy....
So,.......
What Exactly is the Question.........

Any 305 Block built After 1986 will Fit.....
A 305 Block built Before 1987 will have Flywheel Coupler fitment issues.....

 

[Don S]

Re: Merc. V8 305 Identification Help

Your present engine also has roller lifters and a single piece rear oil seal.
PS: That engine was manufactured in Sept. 94

 

[eztiger12]

Re: Merc. V8 305 Identification Help

Holy smokes

How did you guys figure that out so fast......can you please explain how you get all that information from the serial number I supplied.....I've been at it for days.

All the input you guys can give me is appreciated, I'm not a mechanic but a great DIY er. Good with cars but this is my first boat.......

I've also read something about rotation.......how do I know if it's standard or reverse........?

I was planning to find a block and just swap the tin on it.........so any advise is excepted.

Should I be looking at certain upgrades while I'm at it........don't want to spend a fortune though................


Another question.....can I remove the engine without removing the external stern drive........I did purchase a Seloc manual but it's not always clear cut.


Thanks a lot
Don S and Bond-O

 

[Don S]

Re: Merc. V8 305 Identification Help

Other than the year, you can go to Mercury Parts Express click on Parts for Mercury Marine Products punch in your SN and it will take you to the parts breakdown. Then just follow the SN breaks to get the right stuff.

I worked for a Merc dealer and have the year info.

 

[180shabah]

Re: Merc. V8 305 Identification Help

I've also read something about rotation.......how do I know if it's standard or reverse........?

It is standard rotation, counter rotating engines were used on twin engine setups.

...Should I be looking at certain upgrades while I'm at it........don't want to spend a fortune though................

Vortec cylinder heads will really wake that engine up. Or, since you are replacing the block, now is the perfect time to install a 350 instead, they are the same engine, just more cubes, and substantially more power.

OR

You could do both, swap in a 350 with vortec heads for an honest 300hp when fead with a 4bbl.

Of course, any power increases will require gear/prop changes to compensate.

Another question.....can I remove the engine without removing the external stern drive........I did purchase a Seloc manual but it's not always clear cut.

Get rid of that seloc, it is crap. The factory service manual will tell you that the drive must be removed for engine replacement.

Here is a free Online Manual for your drive

Good luck,
John

 

[eztiger12]

Re: Merc. V8 305 Identification Help

Thanks to both Don S and 180Shabah...

My delema is a cracked engine block (on the port side).........
I had a friend (mechanic) come over today and confirmed my initial findings...

The block is definately cracked, but it seems to be an external crack. The engine starts and runs very strong and smooth.
From our findings, there is no water in the engine oil.........

The crack has already been covered with epoxy, I imagine by the previous owner. The epoxy job was very poorly done and is now leaking water through the epoxy (I should say pissing water).

I'm planning to remove the epoxy (don't know how hard that is going to be) to find out the size of the crack. Since the epoxy patch is approx. 6" x 3", (it starts right after the front engine mount and ends right before the rear freeze plug) it is hard to tell how big or long the crack is
.
My gut feeling is that it is beyond repair..........

Now for the upgrades if I have to change my block.........................

180Shabah........you suggested to go with the 350........
Would I be able to swap all the tin parts from my 305 onto the 350 or would I have to replace certain parts?
If so, which parts would have to be replaced?

Would the 350 fit in without modifications ?

By the way.....thanks a lot for the manual John

 

[180shabah]

Re: Merc. V8 305 Identification Help

The 305 and 350 use the same(different cylinder bore diameter) block, ALL of you accessories will swap without modification. Just don't use an engine older then 1988, you will have to replace your flywheel, coupler and starter if you do. Also, you will not want to use the 305 heads on a 350, they increase compression ration too much. So either get a long block, make sure to get the larger heads if you do upgrade to a 350.

 

[eztiger12]

Re: Merc. V8 305 Identification Help

John you've been of great help......

I've been working on the boat today......and finally cleaned the epoxy off the block not only to discover a crack but a gash.....

John

If I understand well, I can drop a 350 in there as long as it's 1988 and earlier (newer).
I also understand that my 305 heads won't fit on the 350......I was planning to find a block with heads, pistons, cam...etc.

Can I but my 305 intake and carb on the 350?.
My carb is a 2 bbl ........would that be stupid to do or would I still get good performance out of a 350 with a 2bbl?
WOuld there be a difference between a 305 2bbl and a 350 2bbl.

If a 4bbl is the only way out on the 350.....what could a 4bbl cost?

You also mentionned.... "Of course, any power increases will require gear/prop changes to compensate".

I have no problems with changing the prop but have no idea how to change the gears...that might just be a little much.

Can I get away by putting in a 350 with a 2 or 4bbl and keeping my gears and prop or just changing only the prop?

My Alpha one indicates 165 gears if that makes sense.......it's on the left of the serial number....I figures it might be the gear ratio.

Sorry for all the questions

 

[Bondo]

Re: Merc. V8 305 Identification Help

Ayuh,........
You could run the 350 on your present Carb,+ Intake,.....
But,.......
If you throw the few hundred bucks at a 4bbl,+ matching intake,.......
Your Smile will be Much Bigger when it's Done......
And,......
If you up-grade to the Vortec Heads,..... You'll need a new Intake anyways.......

The 350s usually run a 1.5/1 gear ratio,....... so does many 305s...
With the 165/1,...... You might get by with a 25" prop,.....
Or you'll have to Regear the drive....

 

[Bondo]

Re: Merc. V8 305 Identification Help

Ayuh,......

 

[180shabah]

Re: Merc. V8 305 Identification Help

What Bond-o said