CRD
New member
I have spent hours trying to find out what the serial numbers mean on my Mercruiser 3.0 inboard engine. Can anyone help please?
BLOCK 3.0L 4CYL RO
051077N
168391
BLOCK 3.0L 4CYL RO
051077N
168391
Mercruiser 3.0 Serial numbers
- Thread starter CRD
- Start date
Andy Cox
Member
Hi CRD
They don't look like valid numbers.
Every Mercury / Mercruiser product has historically used a code beginning with a digit, followed by a letter followed by six digits, so it would look like 0L123456 or later models, I think post 2007 ish would be 1A123456 etc.
The serial number is located in two places. On a label on the black plastic flame arrestor cover and on a small ally label riveted to the block just above the starter motor. the label on the flame arrestor cover has a habit of wearing out and becoming illegible.
If neither of those numbers are there, an idea of the age of the engine is likely to produce at least a serial number range. What sort of age is it?
I suspect the numbers you are looking at are probably GM numbers of some sort.
Hope this helps.
Andy
They don't look like valid numbers.
Every Mercury / Mercruiser product has historically used a code beginning with a digit, followed by a letter followed by six digits, so it would look like 0L123456 or later models, I think post 2007 ish would be 1A123456 etc.
The serial number is located in two places. On a label on the black plastic flame arrestor cover and on a small ally label riveted to the block just above the starter motor. the label on the flame arrestor cover has a habit of wearing out and becoming illegible.
If neither of those numbers are there, an idea of the age of the engine is likely to produce at least a serial number range. What sort of age is it?
I suspect the numbers you are looking at are probably GM numbers of some sort.
Hope this helps.
Andy
CRD
New member
Thanks Andy, that makes a lot of sense. The engine is about 3 years old and those numbers came off a paper label which is still stuck to the block.
The original numbers are still on the flame arrester so I can use those when ordering spare parts. The original number are:
It is raw water cooled but I am planning out a sealed system using large copper tube
The original numbers are still on the flame arrester so I can use those when ordering spare parts. The original number are:
It is raw water cooled but I am planning out a sealed system using large copper tube
CRD
New member
Thanks Andy, that makes a lot of sense. The engine is about 3/4 years old and those numbers are on a paper label still stuck to the side of the block.
The original number is 0D 56........ Can't remember exactly. The original numbers are still on the flame arrester so I will use them for any spare parts.
I am drawing up plans to turn it from raw water cooling to seal block useing large diameter copper pipe 4-6 inches for the outer tube of the heat exchanger. It seems like a good engine but being cooled by sea water horrifies me!
The original number is 0D 56........ Can't remember exactly. The original numbers are still on the flame arrester so I will use them for any spare parts.
I am drawing up plans to turn it from raw water cooling to seal block useing large diameter copper pipe 4-6 inches for the outer tube of the heat exchanger. It seems like a good engine but being cooled by sea water horrifies me!
QBhoy
Well-known member
Andy hasn’t it nailed above. Usually on the air filter cover or near starter motor. The latter, certainly being the case on the other GM V engines at least.
QBhoy
Well-known member
What are you needing to know anyway. Just in case anyone can help.
It’s a 3.0 litre 4 cylinder and 135hp in most recent form and much older versions being 140hp. Usually mated tk am Alpha one gen 2 leg most recently, previously gen 1 and pre Alpha before.
Great reliable engines and good on fuel. Slightly harsh in refinement but do the job and found in many many many boats all round the world.
It’s a 3.0 litre 4 cylinder and 135hp in most recent form and much older versions being 140hp. Usually mated tk am Alpha one gen 2 leg most recently, previously gen 1 and pre Alpha before.
Great reliable engines and good on fuel. Slightly harsh in refinement but do the job and found in many many many boats all round the world.
Bigplumbs
Well-known member
There are literally thousands of these engines that are raw sea water cooled. It will be fine as it is
Andy Cox
Member
CRD, you may find these pics helpful.
They show the different components used in the two cooling systems.
To help you carry out the work itself, you'd find a Clymer or Seloc workshop manual useful as they both contain cooling flow diagrams for both systems to help you understand them.
In fairness though, as Bigplumbs has already said, there are a LOT of these GM engines out there, 4cyl, 6 cyl and 8cyl and if properly looked after they will go on for ever. However, with the raw water cooled set up you need to consider the manifolds and exhaust risers as consumable items, requiring regular checking and replacement probably every 8 - 10 years or so.
Andy
They show the different components used in the two cooling systems.
To help you carry out the work itself, you'd find a Clymer or Seloc workshop manual useful as they both contain cooling flow diagrams for both systems to help you understand them.
In fairness though, as Bigplumbs has already said, there are a LOT of these GM engines out there, 4cyl, 6 cyl and 8cyl and if properly looked after they will go on for ever. However, with the raw water cooled set up you need to consider the manifolds and exhaust risers as consumable items, requiring regular checking and replacement probably every 8 - 10 years or so.
Andy
CRD
New member
Thank you Bigplumbs I will leave it as it is, and basically "look after" it
CRD
New member
Thank you for all your advice and the diagrams are great!
CRD
New member
Yes you are right, it is mated to an Alpha 1 gen 2 leg The unit is about 3 years old so should have a lot of life in it yet then?
QBhoy
Well-known member
Certainly. Keep her well serviced. Oil and filters every year and fresh drive oil too. Check those bellows religiously every year and replace every few years. Especially if left in the water.
Maim problems with these are through lack of maintenance. The exhaust can rot through and allow water into the engine.
If not winterised properly the blocks are well known to freeze and crack. There are many out there with dodgy liquid metal repairs on the block after such a thing.
Get the right prop to have it in the Rev range recommended, so there’s no stressing the wee thing. Don’t like over pitch load on the engine and don’t like over revving with too little pitch.
Every one I’ve ever heard usually has a slight ticking noise from the top end valve gear. Don’t worry about it. They just do that.
Always found that the rock oil MP4 oil does a great job of smoothing them out, over the oem quicksilver 25-40 oil. This stuff tends to loose its blend easily compared to the rock oil 15-40.
Keep her frequently serviced and it will outlast the boat. Still omenty of these around from the 70’s and 80’s.
Maim problems with these are through lack of maintenance. The exhaust can rot through and allow water into the engine.
If not winterised properly the blocks are well known to freeze and crack. There are many out there with dodgy liquid metal repairs on the block after such a thing.
Get the right prop to have it in the Rev range recommended, so there’s no stressing the wee thing. Don’t like over pitch load on the engine and don’t like over revving with too little pitch.
Every one I’ve ever heard usually has a slight ticking noise from the top end valve gear. Don’t worry about it. They just do that.
Always found that the rock oil MP4 oil does a great job of smoothing them out, over the oem quicksilver 25-40 oil. This stuff tends to loose its blend easily compared to the rock oil 15-40.
Keep her frequently serviced and it will outlast the boat. Still omenty of these around from the 70’s and 80’s.
QBhoy
Well-known member
What boat is it on ? Always been amazed at their ability to push along boats you’d never imagine they would.
Bigplumbs
Well-known member
For information mine is on a Fletcher 19 Sports Cruiser. I can get about 30 knots and she is quite a big boat for a 135 hp engine
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CRD
New member
The boat, I am told is a bit of a classic, Tremlett 21 Sportsman built at Topsham near Exmouth.
