Help finding year of Mercruiser engine!

[Jibabadebadido]

So I bought a 2002 Four Winns with a swapped engine. The mechanic who inspected it said that it was an omc cobra 3.0 with a mercury outdrive. Basically I want to find the year of the omc engine so I know year to look up for parts. Currently I am changing the spark plugs.

Unfortunately there isnt a sticker for a model number. These photos are all the numbers I could find...

Edit: Started in the Omc forum and was moved in here. Got most of my answers (I will be needing to buy Merc parts for it and not omc) but it might be cool knowing if anyone else uses an omc block with everything else, including the outdrive, Merc??

 

[Scott Danforth]

With the 3.0, very little changed over the years. Spark plugs same for all except the efi 3.0

 

[Lou C]

Right, the only things that may vary were the ignition system (Merc Vs OMC) and the carb. I wonder if whoever swapped the engine in, re-rigged it with the distributor, intake/exhaust manifold and the carb from the original Merc engine. If so then just follow the Merc specs for that year. The grey paint is a good clue that it was originally an OMC Cobra power plant. Volvos made during the joint venture time period (94-98) would also be painted that same color.

the intake/exhaust manifold, what color is it? If grey, then its the OMC one, if black its the Merc one unless someone painted it grey to match the engine.

 

[Jibabadebadido]

With the 3.0, very little changed over the years. Spark plugs same for all except the efi 3.0

Ok, well that's good then! I just got confused when I looked it up and they gave two different plugs for the year. Currently it is using the rv15y4 but 3 of them are pretty black with carbon and the fourth is pristine so I was figuring out if they were the wrong plugs before I start trouble shooting other problems that may have caused it. [h=1][/h]

 

[Jibabadebadido]

Right, the only things that may vary were the ignition system (Merc Vs OMC) and the carb. I wonder if whoever swapped the engine in, re-rigged it with the distributor, intake/exhaust manifold and the carb from the original Merc engine. If so then just follow the Merc specs for that year. The grey paint is a good clue that it was originally an OMC Cobra power plant. Volvos made during the joint venture time period (94-98) would also be painted that same color.

the intake/exhaust manifold, what color is it? If grey, then its the OMC one, if black its the Merc one unless someone painted it grey to match the engine.

Yeah they did such a good job equipping it with mercury parts that I thought I was buying a murcruiser engine when I bought it so I definitely over paid for an older engine. I guess as long as it runs well then I don't care.

I believe the exhaust manifold is black with chips in it that show gray underneath. Hmm I wonder if someone painted it to look different. Do you mean follow the merc specs for that year to find the spark plugs or for other parts?

Here are some photos of the engine if it helps!

 

[Lou C]

Looks like they used the Merc valve cover. The valve covers were different because the Merc one used has bosses on it for the shift/accel linkage attachments, whereas on the OMC they used a standard valve cover and a bracket for the Cobra shift linkage/ESA. On the intake/exhaust manifold, it is likely a Merc piece because the original OMC ones had 'OMC' cast into it. Only thing I see that I don't like is the buggered up carb fuel line nut and the overtightened nut for the flame arrestor.
The distributor looks like an OMC piece (Prestolite), judging by the grey color. Is it a points or electronic distributor? This is one thing for sure you need to find out as the points/condenser are a regular maintenance item. If this is the case, you would have to use the OMC specs for setting the points. The plugs should be the same, but there can be differences over the years.
If you have an OMC points distributor:
point gap: 0.019" (0.5mm) dwell 31-34*
timing (regular gas, 1*BTDC, premium gas 4*BTDC)
plugs: ACMR43T or Champion RV8C gap, 0.035" or 0.9mm

 

[Jibabadebadido]

Looks like they used the Merc valve cover. The valve covers were different because the Merc one used has bosses on it for the shift/accel linkage attachments, whereas on the OMC they used a standard valve cover and a bracket for the Cobra shift linkage/ESA. On the intake/exhaust manifold, it is likely a Merc piece because the original OMC ones had 'OMC' cast into it. Only thing I see that I don't like is the buggered up carb fuel line nut and the overtightened nut for the flame arrestor.
The distributor looks like an OMC piece (Prestolite), judging by the grey color. Is it a points or electronic distributor? This is one thing for sure you need to find out as the points/condenser are a regular maintenance item. If this is the case, you would have to use the OMC specs for setting the points. The plugs should be the same, but there can be differences over the years.
If you have an OMC points distributor:
point gap: 0.019" (0.5mm) dwell 31-34*
timing (regular gas, 1*BTDC, premium gas 4*BTDC)
plugs: ACMR43T or Champion RV8C gap, 0.035" or 0.9mm

Wow, that is a ton of great information for me thank you! Unfortunately half of this stuff I don't understand but thats why I am hear to learn xP i will make sure if i see an omc on the exhaust manifold or not and I'm glad you told me so I can figure out the carb file line nut and flame arrester issues. Also I will have to figure out the distributor question as well as I don't know the answer to it but like you said I will need to know for the future.

That's good information on the plugs too, hopefully I will get it figured out. I don't even know if it's from the 80s or 90s. Like I told Scott the ones that are in there now champion rv15y4 but three of them are black with carbon and one looks brand new so I questioned if they were the correct ones

Thanks for the info though!

 

[Bondo]

The mechanic who inspected it said that it was an omc cobra 3.0 with a mercury outdrive. Basically I want to find the year of the omc engine so I know year to look up for parts. Currently I am changing the spark plugs.

Ayuh,..... Welcome Aboard,...... If this boat has an Merc Alpha drive on the back of it, it's a Mercruiser driveline, Not an OMC,....

You oughta be searchin' for the Mercruiser serial numbers to buy parts for it, Not OMC,....

In yer pictures, it Appears, somebody used an ole OMC, Long Block, to replace the original,....
Only the Long Block,..... Forgetabout OMC,..... saved yerself the headache,....
Verify it's got an Alpha drive, 'n I'll move yer thread to the Merc forum,.....

Yer spark plug problems Could be that the carb is runnin' too rich, blackin' the plugs,.....
Is the clean plug the aft plug,..??
If so, look for a leakin' riser gasket at the manifold,....

The spark plug, AC Delco MR43T should be the plug for that motor,....

 

[Lou C]

The only thing I'm seeing that might be relevant to tune ups, and might still be OMC, is that distributor. Take off the cap and see if it looks like this inside, if so its not the Merc electronic distributor and you have to use the specs I gave above. Seein' the grey paint on it made me think its still the Prestolite, or a Delco....OMC used Prestolite, Delco and Mallory, the 1st 2 used screws to hold the dist cap on, the last used clips...at least that's what I see in my OMC shop manual....

 

[Jibabadebadido]

Ayuh,..... Welcome Aboard,...... If this boat has an Merc Alpha drive on the back of it, it's a Mercruiser driveline, Not an OMC,....

You oughta be searchin' for the Mercruiser serial numbers to buy parts for it, Not OMC,....

In yer pictures, it Appears, somebody used an ole OMC, Long Block, to replace the original,....
Only the Long Block,..... Forgetabout OMC,..... saved yerself the headache,....
Verify it's got an Alpha drive, 'n I'll move yer thread to the Merc forum,.....

Yer spark plug problems Could be that the carb is runnin' too rich, blackin' the plugs,.....
Is the clean plug the aft plug,..??
If so, look for a leakin' riser gasket at the manifold,....

The spark plug, AC Delco MR43T should be the plug for that motor,....

Thanks for the welcome and the information!

Yeah it's definitely a merc drive. I am assuming one of the owners cracked the original block and replaced it as cost effective as they could.

Yeah I figured the black plugs would be just a minor adjustment to fix but it's actually the front most plug that is in perfect condition. Now there is a possibility that he could have changed only that one before the winter and its only been ran once since I bought it from the mechanic who took a look at it. But I will definitly look at the riser gasket, thank you! And knowing the spark plugs help me out a lot!

Here are photos just for reference...

 

[Jibabadebadido]

The only thing I'm seeing that might be relevant to tune ups, and might still be OMC, is that distributor. Take off the cap and see if it looks like this inside, if so its not the Merc electronic distributor and you have to use the specs I gave above. Seein' the grey paint on it made me think its still the Prestolite, or a Delco....OMC used Prestolite, Delco and Mallory, the 1st 2 used screws to hold the dist cap on, the last used clips...at least that's what I see in my OMC shop manual....

Hmmmm interesting so I pulled it off and it does look different. So then it is a merc part? Haha thanks for figuring this out with me!

 

[Bondo]

Yeah it's definitely a merc drive.

Ayuh,..... Then I'll move this to the Merc forum,....