Last year for 4.3L Mechanical Fuel Pump?

warrenmudd

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When I bought my 1992 Bayliner 2252, the PO (Previous Owner) said it had a completely rebuilt, but one year newer, engine. The cowling serial number decal shows the Engine SN as 0D807679, the Transom ID as 0D694614, and Sterndrive SN as 0D731120. One issue I have: the boat is 90 minutes north at the marina for the summer, so to do any maintenance I have to plan a day off work to get there. I went to chase some fuel issues down, and to my surprise I spy a mechanical fuel pump (Mercury Marine flange ID M60315) that is obviously showing it's age. I think I found my fuel delivery problem.. While this is the proper mech fuel pump for a 262 V6, it isn't for a 1992 or 1993 engine. So, I'm wondering, what was the last year they put a mech fuel pump on the 4.3L Alpha One engine (262 V6)? And what would that last serial number be I wonder? Serial Numbers.jpg
 
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achris

More fish than mountain goat
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Your engine by that serial number is a 1992 (I edited your post to put the right number in, hope you don't mind). And the parts diagram shows an electric fuel pump. If you have a mechanical pump, then the last year of those was also 1992, but ended with serial number 0D714106. Yours was one of the first to have electric. But, what your seeing means at some stage the block has been replaced, and with one of the previous generation. By the serial number you should have a Gen II block (don't get a V6 gen II mixed up with an Alpha One Gen II sterndrive). But by seeing a mechanical fuel pump, you have a Gen I block. And no, it's not possible for someone to have put a mech pump on a Gen II block. The Gen II blocks were cast with no fuel pump mounting.

HTH,

Chris...........
(Another possible reason is the company who installed the engine put the wrong tag on. Have a look at the actual engine serial number tag and verify that number. If there's no tag, then ^^^ may be your answer. The tag is above the starter motor.)
 
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warrenmudd

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Okay, phase 2. I have now determined that the PO repowered my boat rebuilding a 175/4.3L Alpha One lower end (block), and then reinstalling all of the upper end stuff from the original (0D807679) Gen II engine. So I'm calling my pedigree as two engine serial numbers (0D714106 for the lower end, 0D807679 for the upper).

I have triple checked the timing. 8 deg. BTDC at idle, off the timing mark scale (goes up to about 12 deg) at 2000RPM, so the timing seems to be advancing.

The mechanical fuel pump looked older than me, so I replaced it with a new unit. 3 hour pretzel-man ordeal trying to keep the little internal pushrod depressed uphill into it's bore while simultaneously inserting the pump lever into the impossibly small opening. Wish I had that electric fuel pump, despite the cost.

All 3 of the fuel filters (fuel filter/water separator, fuel pump internal filter, carb inlet screen) are pristine clean. I have not specifically checked the fuel pressure while running, but I have confidence it is well within specs (new fuel pump, no restrictions, clean filters).

Engine starts immediately and idles very smoothly when warmed up. It actually idles pretty smoothly while warming up. It runs good and strong out of the hole, and runs smoothly right up to 2700 RPM for cruising (about 22 mph). It will run all the way up to 3000 RPM, but after 10 seconds or so it will start to intermittently miss and hesitate. Won't go above 3000 revs at WOT. I haven't checked the throttle linkage to see if there is any restriction, not sure how to adjust that if it's possible. Advice on how to check it?

I'm thinking now it is in the ignition. I think if it was fuel or carburation it would affect the lower rev performance, which seems pretty solid. But I'm clueless as to how to troubleshoot the Thunderbolt system.

Any clues?
 

warrenmudd

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I thought of that, but just last year installed a completely new vent system including a Racor LG100. It previously only had a straight-thru vent line with only a loop in it to try to catch overflow! So I'm reasonably sure the vent line is open all the way. The symptoms were the same before and after the Racor was installed.
 

achris

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Easiest way to determine if it is an ignition system is to have someone else drive the boat while you hold a timing light on the timing marks... If it's electrical, you'll see it. But to me, it sounds fuelish.... Especially as it is so rev specific. What carb, Weber or Rochester? Webers are real simple to pull apart and clean/reset. Rochesters, not so much.

Chris.....
 

warrenmudd

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Not a Weber. Maybe either Rochester or Mercarb. I'll be able to check next weekend. I also went ahead and bought a new coil, fairly cheap, easy to install, and one less thing to diagnose or worry about.
 

warrenmudd

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Update: suspicious of the coil, I bought the correctly indicated new part, a Sierra 18-5438, which seems to be the coil for almost every Mercruiser of this vintage. The old coil came out, and it looked as old as the fuel pump I replaced. But when the new coil was installed, the engine would start right away and then immediately die. Try again, start and die. Many times. So, out came the new coil and back in went the old. Rochester carb I think, how do you tell? Kind of running out of ideas here...
 

Bondo

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But when the new coil was installed, the engine would start right away and then immediately die. Try again, start and die. Many times.

Ayuh,..... Is there Power at the coil's (+) terminal, when it dies,..??
 

achris

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Rochester carb I think, how do you tell? ...

How many idle mixture screws? One=Mercarb, 2=Rochie..... (I assume since you think it could be a Mercarb that we are talking 2 barrel, not 4)....

Here's how the options were.
4.3LX was a 4barrel engine, either Weber 9600 or Rochester Quadrajet.
4.3L was a 2 barrel engine, either Mercarb or Rochester (see above on how to distinguish)...
 
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