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OMC 260 Inboard, identification and Fuel Pump replacement.

Dav Yag

Dav Yag

New member
I have a boat that I'm trying to get the engines running on. I'm pretty sure the fuel pumps need to be replaced, but I'm having trouble identifying the right part to order, as I'm not 100% sure of the engine type and each engine actually has a different fuel pump currently installed. I also want to make sure I'm installing properly for safety, but I am a novice.

Q: Why do I think it's the mechanical fuel pumps?
A: Neither engine has run regularly in years, and won't turn over now. And I found I can get running if I bypass the fuel filter and pump lines, with a portable tank directly into the carb on the starboard side. On the port side I just poured some gas directly into the carb and it kicked in for a sec.

Q: What do I know about the engines?
A: They have OMC 260 clearly labeled on each. Other markings I can find are: "GM-2", "340234", "Firing Order 18436572". The boat came with an OMC Inboards service manual. The manual covers many models, but I found one page listing V-drive models where a previous owner penciled in arrows indicating Starboard -> Model 260 #990326A and Port -> Model 260 #990330A (also numbers for Transmission OMC Part and Warner Part). I feel like that's my best Rosetta Stone discovery.

Q: What do I know about the fuel pumps?
A: The port side engine has the marking Carter 0-3000, and it has what I think is the vent for the fuel safety discharge, if I understand such things correctly. But it is not hooked up to anything(!!). The starboard side fuel pump has no marking other than 40991 on it. That one actually looks the same color blue paint as both engines, so I suspect it might have been the original. It does *not* have an outlet for rupture discharge like the other one. The port side fuel pump is colored differently in addition to having a different body style. Neither engine's flame arrestor has a connector for a fuel line discharge as far as I can tell.

I *think* what I need to do here is
1. Get a marine replacement for Carter 0-3000 for both (so more like the port side)
2. Figure out how to properly hook up that rupture/discharge outlet

I've already ordered a wrong fuel pump once, because I was confused about the engine (at the time I thought it was a Chrysler sadly). I was trying to use ChatGPT to help figure this stuff out, but I've given up on that. It happily agreed that it was a Chrysler despite giving it the "GM-2", "340234" info above. I'm hoping the smarter intelligences here can help make sure I'm on the right path....

For some reason I can't successfully add photos here, but I can add a YouTube link, so I made a slide show that depicts: the starboard engine, a few shots of the starboard fuel pump removed, and a final shot of the port fuel pump still mounted).

 
Resize your photos to < 1Mb.
You might have to have 6 posts before adding photos is allowed, I think it’s an anti spam measure.
 
Hi Dav, I am not a pro, but I have had a lot of experience with my Ford 302, which there are many threads below. It looks like a Chevy 305. See the YouTube link to see if it looks about the same. You didn't mention the year, but this is a 1981,
I have had best results with the carter fuel pumps - I have gone through 4 of them, most were like your starboard side ones that never seemed to give enough pressure - the pressure should be about 5-6 psi from the pump.
The discharge tube should be clear marine tubing, I believe 1/4" going to the carb, which there should be a nipple there for it. If not, perhaps could be through the flame arrestor. If you see fuel in this line, your fuel pump diaphragm is broken, so probably doesn't matter where it goes. It could just go to a reservoir, so it doesn't create a fire hazard.
You also mentioned that it wouldn't turn over, which sounds like a starter problem. I have been through 4 starters as well, and if you have the old- style starter, I recommend upgrading to a PMGR starter for better torque and uses less amps. The wiring is slightly different, but not complicated. May also be the solenoid, which I have been through 6 of them, or the wiring connections, which may need to be cleaned up.
 
Best thing to do is find out what model number your OMC engine is and get a factory shop manual. You can still find these & it’s very helpful. I replied to your YouTube link, you need a Carter marine fuel pump for a Chevy small block V8.
 
Dav Yag said:
Q: Why do I think it's the mechanical fuel pumps?
A: Neither engine has run regularly in years, and won't turn over now. And I found I can get running if I bypass the fuel filter and pump lines, with a portable tank directly into the carb on the starboard side. On the port side I just poured some gas directly into the carb and it kicked in for a sec.
Click to expand...
Let's get our language straight.....
Above you write....
"A. Neither engine....and won't turn over now"

In my opinion "turn over" is an expression that should be clarified & theneliminated from this discussion.

Now my question....
Do the engines crank when you select the key to start? I assume yes they do because next you say they start if you bypass the pump & pour fuel direct into engine.

Neil above in post 3 assumes "turn over means "crank" & believes you have a starter problem.
 
Do the engines crank when you select the key to start? I assume yes they do because next you say they start if you bypass the pump & pour fuel direct into engine.

Neil above in post 3 assumes "turn over means "crank" & believes you have a starter problem.
Click to expand...
Sorry, yes bad terminology on my part. Both engines crank when turning the key, but they fail to actually start running (except when I was bypassing fuel line components).
 
Looks like I can upload photos now. Here are some more of the carburetor and current flame arrestor. Not clear yet where the fuel pump discharge tube would go into this, but I'll dig into the Rochester QuadraJet docs I can find....

And yeah, louc, I am expecting a carb clean/rebuild is likely coming up next as well.

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It's 7 deg F with light snow & all my reference materials are out in my shop with the geat turned off. So I did my best quickly.

Your engines are indeed 1975 models. Apparently, Marine Engine parts look-up doesn't include straight inboards.
 

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Fuel pump item #25 is P/N 980865. I do not see the tube to carb that you are refering to. That is about the vintage they began showing up on engines. But I don't know exactly when.

I'm having issues attaching pics today. Will try to add others in following posts.
 

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Last pics, Microfische cards & cover of model year book. I believe I'm the only guy on the block with these references.
 

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OMC GM engines don't seem to show the fuel pump overflow tube until 1978 models. So most likely yours didn't have them. I'd also guess replacement fuel pumps all are built with a hose nipple.
The function is to direct any fuel (there should be none) from the pump to the carb air horn so it doesn't fill the bilge with fuel. Depending on how big the leak is it may or may not cause any running issues. A huge leak could vary well flood the engine. So long story short, you could install a fitting into the flame arrestor as a retrofit. I don't see a good place in your pics to install to the carb air horn without blocking flame arrestor installation.
 
The boat is a 1977, but the manufacturer probably had some older engines to get rid of. So, Droid has confirmed that it is a 1975 GM and it's a straight inboard without any outdrives, correct? Droid has helped me a lot.
I see a barb on your first big picture, which needs to be connected to something, or capped. Not sure exactly what it is. Connecting it to the fuel pump discharge tube will essentially cap it. Or direct it so you can see it and use an overflow reservoir, see link:

Amazon.com: YANMAR OVERFLOW TANK/RESERVOIR YM1602,1610, 1702, 1802, 1810, 2020, & MORE! : Automotive

Buy YANMAR OVERFLOW TANK/RESERVOIR YM1602,1610, 1702, 1802, 1810, 2020, & MORE!: Reservoirs - Amazon.com ✓ FREE DELIVERY possible on eligible purchases
www.amazon.com
 
Droid’s photos (microfiche, how cool!) show OMC part 25 #980865

Google searching on that led to
  • this Carter M61073, which looks like it might work, although the rupture discharge barb and the other in/out fittings seem slightly differently positioned. Maybe that doesn't matter as long as the hoses can connect?
  • Or the Sierra 18-7268
But I can’t find any modern fuel pump so far that matches exactly from #980865. There are ones that looks similar enough perhaps, but then they list what they match its never an exact match. For instance this 18-7268 from this website says it matches 981650 but nothing about the 980865.

Given that I already have two different fuel pumps on the engines, it seems obvious that there are multiple that *can* match, so maybe I shouldn’t be very concerned with an exact match? Like as long as it is an Sierra 18-7268 match and has the rupture discharge barb, and is rated ~5-6 PSI, that’s good to try? How hung up should I be on finding an exact trail from 981650? Particularly since that was probably the original one that didn’t have the modern rupture-discharge outlet.

Even for the possibilities above, prices seem vary widely, I presume cheap ones are not worth the hassle?

As best as I can tell there’s no specific stampings on the carbs beyond the Rochester QuadraJet, but ChatGPT seems convinced it is an 800 CFM model.

Also
- Discharge line: will get 1/4” clear to either to the arrestor if I can figure that out, or at least to a temp reservoir like Neal pointed to.
- will start looking into PMGR starter if I have any starter problems come up!

I appreciate all the help here!
 
If it was mine, I'd go to a later pump, probably the 18-7268. Uses the same gasket & push rod.
If you can adapt the steel line from the original cartridge fuel filter assembly great. If not, dispose of it & install a Sierra spin on assy 18-7848-1 (or Mercury/Quicksilver 35-802893A4 or Q4). You may need to fabricate a mounting bracket. I'd move the whole assy to somewhere convenient but it must be higher than the top of the tank so it doesn't syphon/leak or spill/dribble when you remove the element for replacement. Use USCG type-A fuel line.

As for the carb end of the overflow discharge hose, without putting eyes on it I can't say.
Ist question is there room between the flame arrestor & engine cover for a 90deg hose barb fitting. In other words, say maybe 1" clearance?

A 1/4" 90 degree barb with 1/8NPT threads could be adapted to the flame arrestor but the aluminum is too thin to thread. An aluminum plate would need to be added. Not insurmountable but it depends on your skill level & access to materials.

I'd be hesitant to drill & tap the carb top. I'm not sure if it's thick enough to thread. Maybe, but IDK without a micrometer to measure. Also, it needs to rotate to thread in & maybe there is no clearance? Perhaps find a later engine OMC/MerCruiser, probably doesn't matter & see how the factory did it. I don't remember, it's been 22 years since I ran anything that new.
 
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It looks like a barb in the big picture at the bottom of the carb near the numbers for the intake manifold - looks a little rusted.
Just make sure the pump has the short rocker arm, as the longer is for a Ford. The only reason it would have to go to the carb is just to see it easily and to have an outlet for the fuel to go somewhere so you can see it in the line. Unless the barb in the picture is actually just a plug, or something, I would put it there, or the reservoir mounted on the other side of the engine, so the tubing drapes across the engine or somewhere you can see it easily.
 
That is one on the 2 idle mixture screws. Other is out of view behind the fuel line.

A slow fuel leak from the pump to a reservoir would most likely not cause runability problems & so go unnoticed until it overflows into the bilge.

By returning the fuel to the carb it will be burned or in the event a bigger leak, cause runability (running rich all the way to flooding out). But no fuel would flow into the bilge.

Your link is a coolant overflow reservoir.
 
Yes, it is a coolant reservoir, but it is vented and hopefully it would never be used until you replace the pump. I remember seeing dedicated fuel pump reservoirs but couldn't find one quickly on Amazon. I believe they exist.
 
The new style fuel filter is a good idea, with all 3/8" line and connection fittings. You can see my new filter in the lower right corner with the new bracket I made for it to move it out to the corner there, as it was much bigger than my old one. It also separates any water from fuels with 10% ethanol, which is all we can get in Southern California without paying $10/gal. It is a large Sierra 18-7866 filter and here is a link to the all 3/8" connection base:

You can't really see the clear tubing, but it connects to a barb near the larger metallic fuel line high up on the carb and would just leak into the carb. Your fuel filter should also have all 3/8" MPT fittings with the four-barrel carb and that much horsepower. I have a lot of upgrades with an estimated horsepower of 240 to 270 HP. I could never get enough fuel until I upgraded to all 3/8". It always seemed fuel starved. I remember I had the hardest time finding a fuel pump with 3/8" fittings. Mine for Ford may have been M6696 but am not sure.
I had to go to Summit racing products. Here is a link to one - it doesn't say if it is 3/8" fittings but is for a marine GM 305 or 350 (5.0/ 5.7L). Maybe you can start from there and perhaps call them up. Most common is 1/4" MPT fittings. Some can be drilled out.

Ford 302 4.jpg

see at www.sport-fishing-friends,com
 
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Droid said:
That is one on the 2 idle mixture screws. Other is out of view behind the fuel line.

A slow fuel leak from the pump to a reservoir would most likely not cause runability problems & so go unnoticed until it overflows into the bilge.

By returning the fuel to the carb it will be burned or in the event a bigger leak, cause runability (running rich all the way to flooding out). But no fuel would flow into the bilge.

Your link is a coolant overflow reservoir.
Click to expand...
I have an original marine Quadrajet on my 1988 OMC 4.3 and the nipple for the overflow hose is on the left side front of the carb. I’ll see if I can find a pic….its just to the left of the fuel inlet
 
the attached PDF shows where mercruiser had rochester put the SIGHT tube fitting...thats where the hose from the fuel pump goes if the main pump diaphragm fails. The fitting dumps into the primary bore. Most everybody uses a piece of TYGON hose for the sight tube...you want something that allow you to see if fuel is present in the line...

If you opt for putting a fitting into the flame arrester, make sure the fitting is positioned so that any fuel delivered will enter the primary bores...I'd had to modify a few to keep them from rotating...
 

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Yes that’s exactly how mine is. The other thing I noticed is the bowl vent. The one on the OP’s looks like the standard auto version vent. On mine it has a reverse angle cut to it so if the bowl overflows it is directed to the primary bores. I have seen some that were fitted with J-tubes like on a Holley marine carb but not sure if that was OEM marine.
 
On the vent tubes, most I've seen have been slashed cut, with the low open end towards the primary bores, but have seen a couple straight (though they could have been 4GCs...its been a while). I don't think it matters much as long as the flame arresters are fitted...
 
Hi, all. So I got my new fuel pump, the Carter M61073. The old barb fittings for the 5/16" hose lines are pretty gunky and aren't coming clean even with a wire brush. So I figure I can just get some new fittings, but I'm afraid of getting the wrong parts. The Carter info page clearly states that the inlet/outlet ports are 1/4" NPSF, but in my web searching on what barbed fittings to buy, I'm seeing a lot of NPT which as I understand is a completely different system. Do you know what parts I should be ordering that will fit into this fuel pump and provide a bard for the 5/16" hoses?

Also, the inlet/outlet ports are in slightly different positions than either of the old fuel pumps. I presume that doesn't matter much as long as the hoses can connect, but I also heard that you can "re-clock" fuel pumps. Do you think it's worth doing that?

BTW, I managed to bend the pushrod so I had to pull that out for replacement too 😅. Hopefully I'll be making less mistakes by the time I get around to rebuilding the carbs!
 
get the 1/4" NPT male threaded adapters you need - they will fit fine. Also recommended is a teflon based thread sealer on the pipe threads - I prefer locktite PST.

Need for "Reclocking" is driven by the specifics of the installation - as long as there is no interference and things dont leak, you should be good to go.

Since the steel fuel line was removed and rubber hose used to replace it, at a minimum, make sure it is A1 rated hose at a minimum and secured along its length...
 
The main thing with rebuilding Quadrajets is it is tricky to remove the air horn, and you have to really clean the idle air tubes. Then when putting it back together, be careful with the primary and secondary metering rods....
Quadrajet rebuild, @ 37 years old!.jpg
 
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