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Need Help Decifering ID Tag on Sterndrive

7

79' Slickcraft

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I have a 79' 5.7 OMC with Model #983816 and Serial# J352479. Im trying to order some parts and a service manual but when i put these numbers in, Im struggling trying to find info. Am i missing something? The numbers came off an ID tag on the side of the outdrive. I couldnt seem to find any other info stamped anywhere.
 
I have a 1976 5.0 OMC Ford 302, and the model number has 6 digits 990231and an M = #990231M, which is what I used to find my parts on this website. Also, your model number is lower than mine, which seems strange as it is 3 years newer. My engine serial # is W524031, which is similar in letters and numbers, and I believe the W stands for Winsor, where it was made. Yours is a 1979 Ford 351. You may look again or try punching in an M or something.
Just a guess.
 
You also may need the horsepower, which yours is probably 235 hp for a Ford 351. Also, like on mine, the boat is a 1977, but the motor and drive are 1976.
The engine serial number is usually in back, on top, just ahead of the intermediate unit, and is printed on a metal tag, which may be painted over. look for the tag and rub some paint stripper on it. You said it was J352479.
 
Neal Franson said:
You also may need the horsepower, which yours is probably 235 hp for a Ford 351. Also, like on mine, the boat is a 1977, but the motor and drive are 1976.
The engine serial number is usually in back, on top, just ahead of the intermediate unit, and is printed on a metal tag, which may be painted over. look for the tag and rub some paint stripper on it. You said it was J352479.
Click to expand...
Yea, that and the model number were stamped on a metal tag but its on the outdrive, not on the engine.
 
I asked Grok what the J stood for in your serial number, and he told me:

In the context of a 1979 Ford 351 marine engine with the model number J352479, the "J" likely indicates the engine type as a 351 Windsor (351W) V8 with a 2-barrel carburetor, as this was a common configuration for Ford marine engines during that period. Ford supplied 351W engines for marine applications, often used by manufacturers like Mercruiser or OMC for boats. The 351W was preferred in marine use due to its reliability, widespread availability, and performance characteristics, such as a 4.000-inch bore and 3.500-inch stroke, producing around 200-250 horsepower depending on the setup.

The "J" in the model number aligns with Ford’s VIN or engine code conventions, where it typically denotes a 351W with a 2-barrel carburetor in marine or vehicle applications. The 351M (Modified) was less common in marine use but not impossible, so the "J" could theoretically point to a 351M in rare cases. However, marine engines in 1979 were predominantly 351W-based due to their established use in boating applications. The remaining digits, "352479," are likely a serial or production number for the engine.

To confirm whether it’s a 351W or 351M:
  • Check the engine block casting number: Look for a code near the starter or on the block. For example, "D9AE" or "C9AE" typically indicates a 351W, while "D7TE" or similar might point to a 351M.
  • Intake manifold width: Measure the intake manifold. A 351W has a narrower intake (about 10.7 inches), while a 351M is wider (around 12.5 inches).
  • Thermostat housing: On a 351W, it’s on the intake manifold; on a 351M, it’s on the block.
https://grok.com/ sign up for free.
 
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Opps I was wrong. It is a GM engine. I asked Grok your original question and he said:

The 1979 5.7L OMC (Outboard Marine Corporation) engine with model number 983816 and serial number J352479 is a V8 inboard or stern-drive marine engine, commonly used in boats during the late 1970s and 1980s. Based on the information available, here’s a detailed overview of the engine:


General Specifications​


  • Engine Type: 5.7L V8, 4-stroke, gasoline-powered marine engine.
  • Displacement: 5.7 liters (350 cubic inches).
  • Horsepower: Typically rated between 175-250 horsepower, depending on the specific configuration and application (e.g., stern-drive or inboard). For 1979 OMC applications, it’s often closer to 190-225 HP, but exact output depends on the carburetor, ignition system, and other components.
  • Bore and Stroke: Approximately 4.00 inches (bore) x 3.48 inches (stroke), standard for a small-block V8 of this era.
  • Fuel System: Likely equipped with a carburetor (commonly a 2-barrel or 4-barrel Rochester or Holley, depending on the setup). You can verify the exact carburetor model for your engine at sites like Flying Fish Carburetors for remanufactured options.
  • Ignition System: Typically uses a points-based or early electronic ignition system, located under the flywheel. Accessing it requires removing the flywheel from the crankshaft’s tapered shaft.
    https://www.leeroysramblings.com/OMC%207.5hp%201980-1983.html
  • Cooling System: Marine water-cooled, using either raw water (drawn from the environment) or a closed-loop system with a heat exchanger, depending on the boat’s setup.
  • Applications: Used in OMC stern-drive systems (e.g., OMC Cobra or Stringer drives) from 1975-1979, and sometimes into the early 1980s for 3.8L to 5.7L configurations.

Model and Serial Number Details​


  • Model Number (983816): The model number indicates it’s a 1979 OMC engine. OMC used a coding system where, prior to 1979, the last two digits of the model number often denoted the year. After 1979, they switched to a letter-based system (e.g., “INTRODUCES” where each letter corresponds to a number). For 1979, the model number aligns with the production year, confirming it’s a 1979 model.
    https://www.leeroysramblings.com/OMC%207.5hp%201980-1983.html
    https://www.leeroysramblings.com/omc_model_code.htm
  • Serial Number (J352479): The serial number is unique to the engine and helps identify the specific unit for parts ordering or service records. The “J” prefix is typical for OMC/Johnson/Evinrude engines, but it doesn’t directly encode specific details like horsepower or shaft length without further context.
  • Identification Location: The model and serial numbers are typically found on a 1” x 2” aluminum ID plate riveted to the left-hand side of the transom mount bracket (looking forward). If the plate is missing, check the soft plug on the upper rear right-hand side of the engine block, where the model and year may also be stamped (though this practice was more common up to 1979).
    https://www.leeroysramblings.com/OMC%207.5hp%201980-1983.html
    https://www.crowleymarine.com/d/tech_article/locating-omc-model-numbers

Key Features and Characteristics​



Maintenance and Repair Resources​


 
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I have lots of manuals but not a 79. I do have a 1980 service manual it deciphers outdrive numbers. They all start 982XXXX, so the number you found is indeed an outdrive #.

My model number cross reference book from 2005 shows all I/Os from 73 thru 80 use a number system that starts 9902XXX.
Now because your boat is supposedly a '79..... especially if an early build boat, it could have a left over engine. And if a late build, maybe has 1980 engine? Regardless, the service manual and parts book use the engine model # not drive model #.

As far as I remember, the data plate was located near the starter but you are taking me back 45 years or more.

It appears 79 was the transition year from Ford to GM. There was a Ford 250 & GM 185, 200, 230 and 260.
Is your engine GM or Ford? I'm thinking GM because the Ford 351 was marketed as a 5.8 but I don't think boat engines went to metric until later 80s. Maybe you're just using 5.7 out of habit?

You do indeed have a 78 or later mechanical shift lower unit?
 
Neil, your buddy isn't always correct. For example, he says points are located below the flywheel. That is an outboard not an I/O.

I dug a bit deeper and 1981 only used an alpha numeric system starting with 3 digit hp then a series of letters. For example, 120FTHRCIS.
In 1982 they went to a liter designation. For example, 252FPHRCNC. 1st 2 digits were liter, in this case 2.5 (in other words the 120hp) The 3rd digit was always a 2 or 4, so that must be the carburetor size.

The INTRODUCES system only applied to outboards, never an I/O.
 
Droid, you have real experience and intelligence that we all don't have, and Grok's intelligence is artificial, by definition.
It seems to be a GM 350, but I couldn't find the number on this website. All the numbers started with 9902.
 
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As well as in my BRP published model # guide.
Yes. I think its a 350 & not a 351. But there is the remote possibility.
 
Yes but we are old. The GM/Olds/Chevy engine lawsuit was late 70s. After that, they became GM.
I'll bet lots of readers have no idea what I'm talking about now. Or when we talk about dwell or carburetors for that matter.
 
There is a GM marking stamped on the upper intake manifold. I also do know that it is a 4 barrel Rochester carberator and on the the top of the outdrive where my oil fill screw is located there is another nameplare that says "OMC 5.7L". Thats the only reason I say its a 5.7
 
Seems something has gotten swapped out. So, I asked my friend Grok this question and got this answer:

How can I verify the model number and serial number of what appears to be a 1979 OMC 5.7 GM outdrive which the motor or the outdrive may have been swapped out?

Verifying the model and serial number of a 1979 OMC 5.7 GM outdrive, with the possibility of a swapped motor or outdrive, involves locating identification plates, decoding the numbers, and accounting for potential mismatches. Since you’ve specified a GM 5.7L engine, I’ll tailor the process to focus on that engine type and the OMC Stringer 800 outdrive typical for 1979, while addressing swap complications. Here’s a concise step-by-step guide:

1. Locate the Identification Plates​

Find the model and serial number plates or stickers on the following components:
  • Outdrive: Check the port (left) side of the outdrive, upper or lower gear housing, or bell housing near the transom. For a 1979 OMC Stringer 800, the plate is often riveted or stamped here.
  • Engine: Look for a plate on the GM 5.7L (350 cid) engine block, typically near the starter boss, valve cover, or flame arrestor. GM engines have the distributor at the rear, confirming it’s not a Ford.
  • Transom Assembly: Inspect the intermediate housing or transom mount for additional plates, as some Stringer models have identification here.
Note: Plates may be rusted, painted over, or missing (especially if swapped). Use a wire brush or solvent to clean illegible plates. If no plates are found, the outdrive or engine may have been replaced.

2. Decode the Model and Serial Numbers​

Interpret the numbers to confirm the outdrive and engine details:
  • Outdrive Model Number: For a 1979 OMC Stringer 800 paired with a 5.7L GM, expect a model number like “982436” or similar (per prior data). The Stringer 800 was standard before the Cobra (introduced 1985). Numbers starting with “58” or “985” (e.g., 584APLRGD) indicate a later Cobra outdrive, suggesting a swap.
  • Outdrive Serial Number: Often starts with a letter (e.g., “W” or “T”) followed by numbers (e.g., W217061). Serials are less critical for parts lookup but help track origin.
  • Engine Model/Serial: GM 5.7L engines have a casting number on the block (e.g., 3970010 for 350 cid) and a serial on the plate. The serial may include a year code, but it’s not always reliable for swaps.
  • Year Confirmation: A 1979 Stringer 800 should lack Cobra-specific codes (e.g., AMH, RGD). If the model resembles a 1985–1993 Cobra, it’s a replacement.
Example:
  • Model “982436” = Stringer 800, likely 1979, compatible with 5.7L GM.
  • Model “584APLRGD” = 1991 Cobra (5.8L, post-1985), indicating a swapped outdrive.

3. Account for Swapped Components​

Since the motor or outdrive may have been swapped, check for mismatches:

Engine Verification: Confirm it’s a GM 5.7L (distributor at rear, 350 cid). If it’s a Ford 5.8L (351W, distributor at front), the engine was swapped, which may affect outdrive compatibility.
  • Outdrive Compatibility: The Stringer 800 uses a 1.5:1 or 1.41:1 gear ratio for 5.7L GM engines. A Cobra outdrive (post-1985) has a dog clutch and different shift cables, indicating a swap. Check prop shaft splines (15 for Cobra, fewer for Stringer).
  • Visual Clues: Stringer 800 outdrives have a tilt mechanism and no cone clutch (unlike Cobra). If the outdrive looks like a Cobra or Volvo Penta SX (post-1993), it’s a retrofit.

4. Cross-Reference with Resources​

Use the numbers to verify details:
  • Crowley Marine: Enter the model number (e.g., 982436) for Stringer 800 parts diagrams.
  • Sterndrive.info: Offers model year charts and exploded views for OMC outdrives.
  • MarineEngine.com or iBoats Forums: Post numbers and photos for community help.
  • 1979 OMC Manual: A service manual for Stringer 800 drives can confirm model codes, but beware of GM/Ford mislabeling.

5. Practical Steps​

  • Clean Plates: Use a wire brush to reveal faint numbers.
  • Document Numbers: Record model/serial numbers from outdrive, engine, and transom. Note the boat’s HIN to confirm the hull year (1979).
  • Check Gear Ratio: Ensure the outdrive’s gear ratio (1.5:1 typical for 5.7L) matches the engine to avoid performance issues.
  • Consult a Mechanic: A marine mechanic with OMC experience can inspect the transom assembly and clutch type (Stringer vs. Cobra) if numbers are missing or mismatched.
  • Parts Lookup: Use Crowley Marine or Southcentral Outboards for parts, but confirm the model before ordering (e.g., upper gear set, seals).

6. Challenges​

  • Missing Plates: Swapped or refurbished outdrives may lack OMC plates. Look for secondary stampings or consult a pro.
  • Obsolete Parts: OMC’s 2000 bankruptcy makes Stringer 800 parts scarce. Try eBay or salvage yards.
  • Swaps: Pre-1988 5.0L/5.7L outdrives are interchangeable, so a 5.0L outdrive could be paired with your 5.7L engine.

Recommendation​

If you find a model like “982436” and a GM 5.7L engine, it’s likely original to 1979. If the outdrive is a Cobra (e.g., “584” codes) or the engine is a Ford, it’s a swap—verify gear ratio and compatibility. Post numbers/photos on iBoats or consult a mechanic for clarity. Share any numbers you find, and I can help decode them further!

Which essentially says to ask Droid.
 
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