1989ish Merc 454 fuel pump
 

Guys,

Next puzzle…..

So last year, we sold our ‘89 Rinker 236 Sport Cuddy to some friends of ours; their first boat. It came stock with a Merc 454 carb engine, no idea of the model. It had had some work done to it prior to our ownership, bored .060” over, mild cam, Edelbrock intake and carb, etc. I replaced the Edelbrock 650 automotive carb with a Holley 750 marine carb. Again, don’t remember the model, but it has jet plates, not screw-in jets. I had also installed a fuel pressure gage with the new carb. We had it running pretty good. Anyhow….

Last weekend, while rolling onto the throttle to take off, he noticed a bit of a sag, or hesitation, which was new. The next day or so he hooked it up to the hose and ran it in his driveway. He noticed that, at idle, it had ~6lbs of fuel pressure, but that dropped to 4.5-5lbs at about 2K RPM. Thinking the fuel pump had gone soft, he ordered what he thought was a replacement. When it arrived, he pulled the fuel pump off, only to realize two things: He’d bought the wrong pump, and that there was apparently supposed to be a spring on the pump pushrod, and it’s now gone.

I know this is a stab in the dark, with damned little to go on, but…..

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Is this pump supposed to have a spring, presumably to hold the pushrod against the cam? If so, where would it have gone? He’s worried about the possibility of it floating loose in the oil pan, and I honestly don’t know one way or the other.

Would an electric conversion be a viable fix? I know there are pumps with built in regulators and block off plate available. Just not sure if it’s always an option.

Thanks. Brad.
(937)545-8991

Very lengthy for a simple question. Lol. The fuel pump arm keeps pressure on the rod and there is no spring in between. Also pretty difficult to get anything other than oil between the rod and block.

Brad,
I have never heard of a Chevy fuel pump having a separate "spring" to hold the pushrod against the cam. The spring in the diaphragm assembly does that. It just looks like a generic Chevy marine fuel pump. Which one did he buy and what is "wrong" about it ?

Look at a Carter pump. You might have to turn the housing to get the inlet and outlet where you need it.

https://www.summitracing.com/parts/crt-m60501

Yup, should be spring under the arm. Not on the pushrod.

https://cimg5.ibsrv.net/gimg/www.off...0043e22f8.jpeg


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SB,

So, I guess the question is, where did the spring go? Is it laying harmlessly in the bilge? Or is it bouncing around inside the crankcase, looking for trouble to get into?. That's the million dollar question at this point.

Also... Would he be better off going electric?

Thanks. Brad.
(937)545-8991

I'm assuming your talking abt the anti-float spring under the lever attached to the fuel pump.
The pushrod goes thru a "tunnel" and there's not a lot of clearance around the sides. Don't think that spring could get past the pushrod. Its most likely laying in the bilge.

I'm running these pumps with an adjustable fuel press regulator.
https://claysmithcams.com/ppf-11-1-b...cal-fuel-pump/

Fuel press is rock solid all the time. Unfortunately, seems they are out of stock at the moment.

ZZ,

Yes. The anti-float spring under the actuator lever is missing, and the friend's biggest concern was where it went. It sounds like there is nothing to worry about. Good news. He's already got a proper replacement on the way. It'll just be a matter of putting it all back together and taking it for a spin. Don't kow if we've solved the sag/hesitation thing that kicked all this off, but it may not have been a real to begin with. We'll see.

Thanks. Brad.
(937)545-8991

if there's a plate that the fuel pump arm goes through ? the spring may be laying in the bottom where the plate bolts to the block, see if you can fish it with a magnet or hook


https://cimg8.ibsrv.net/gimg/www.off...2f8a6a9d98.jpg

Anyone know how to remove the fuel pump arm after pin removal. There’s part of the casting in the way. Sure it’s there for a reason but looked at this thing long enough.

Guys,

So, new fuel pump is in and hold really goo fuel pressure. But....

The boat still has a slight sag, or hesitation, if he gets into the throttle too heavy at take-off; like a ski pull. Boat runs fine, otherwise. My guess is an accelerator pump issue, but I'm a rank amateur at best. Any solid guesses? Places to start the trouble shoot?

Thanks. Brad.
(937)545-8991

Could be. Btw:What kind of carburetor ? Quadrabog or Webber ? Edit: I just saw year, 89, so Prob quadrajet unless replaced over the years.

SB,

Holley 750 Marine. Don't remember the exact model, but it has the jet plates instead of thread-in jets, if that helps.

Thanks. Brad.
(937)545-8991

If new issue, Two likely areas are the red silicone nipple under the acc pump diaphragm and the needle and it’s area under the pump squirter.

It has a plates for the primaries and secondaries?? The only time I've seen a plate is used, it was for the secondaries on a vacuum advance carb and that would make it a 4160

Griff,

It very well could be. That sounds about right, as far as the jet plate goes. I bought the carb several years ago, probably '12 or '13, and haven't even thought about it since getting it dialed in initially. It was a "new" used unit from Ebay. It had supposedly been mounted but never primed. I remember it didn't smell like gas when we unpacked it. But it's been many moons since then. I'll ask.

Thanks. Brad.
(937)545-8991

Just now reading, I didn't think it was the fuel pump. 4.5 lbs of pressure is more than enough for a mild 454. If it ran good last year, and has issues now, suspect ethanol deposits unless it was run with ethanol free religiously. Probably has some trash in it.

TomZ,

Too late. 😁 He's pretty happy with the nice consistent 7lbs he's got now.

He's gonna pull it in the next couple weeks and take it to a local carb shop for a once-over. His boating season is over, for reasons of lifestyle, so he's getting it ready for winterizing and fixes/repairs for next year. The carb shop is dedicated shop that only works on carburetors. He's got a couple of shop engines he tests and tunes carbs on. He refuses to work on them in their vehicles, though, which is odd, but he definitely knows carbs inside and out. The initial hope was to get it figured out before the end of the season, but I guess we got on it too late. 😐😒

Thanks. Brad.
(937)545-8991