Greetings,

First I'd like to introduce myself. Just a humble boater, I wrench by day and drink by night. I've turned my wrenches now for roughly 8 years. I've seen some stuff, I fixed plenty of cars but now that it's my own boat I wanna see what everyone else's opinion is with my boat.

I have a 2001 Baja 272 with a single 502 MAG MPI. Completely stock. I was taking the Mrs. out the other day and the engine had very low power and was making a popping noise. After bringing it down to an idle, the engine stalled and would start/stall out immediately. I've recently done plugs/wires/cap/rotor/fuel filter/oil pressure switch. She ran good all last year, no complaints really. I tested and found my fuel pressure to be at 0 psi. Thinking my brand new fuel filter may be bad a tried a new filter, wix brand, and found that even though I can hear the fuel pump making noise, the new filter isn't filling with fuel.

I now have questions lol
1, does my Gen 6 502 MAG MPI have a threaded or non-threaded fuel pump. I apparently have a quicksilver reman engine. I cannot seem to find my engine serial # tag, I think it's missing. I've looked long and hard trying to find any info on this motor but at this point its a best guess. Near as I can tell, I have a GEN 2 cool fuel non-VTS fuel system.

2, Anyone ever done a fuel pump on one of these boats? It doesn't look fun.

3, Anyone have any other advice for me as far as more things to test? Sounds to me like a great place to start.
AC. I'm thinking Sierra marine 18-35433. Anyone had any luck with some of the cheaper pumps I'm finding on amazon?

Thanks, any input is appreciated. If I can't figure out which pump I need, threaded or non-threaded I guess I'm gonna have to tear 'er down before I can make a fuel pump purchase.

If It helps here are a couple photo's of the cool fuel pump/cooler assy. This should be the same as your as mine was off a 2000.

502 Cool fuel

I don't see any on that link? Attachments to the post, hotlinked, embedded pictures??

Idk sorry to be a debby downer but I didn't see any responses to my post so I gave up and took it to the shop. I'm literally an ASE certified dealer driveability technician so its kinda frustrating for me. Just don't have the time to mess with it really.

Thank you so much for your reply though, I appreciate it!

Its not the filter, but might be the antisiphon valve or the pump. Before you buy a pump, get a gas can and a longer piece of fuel line. Stick the fuel line in the gas can and other to the filter.

This is your motor
https://www.mercruiserparts.com/502-...i-gm-502-v-8-1

The cool fuel model is tough to do but hardest part for most is getting at it. There is a plastic cover which snaps off, then two nuts and washers that hold the pump and cooler in place. The pump should be threaded on the filter end and just O rings on the other. There is a pin (item 9) on the O ring side that gets removed to then be able to remove the fuel line

The cool fuel module
https://www.mercruiserparts.com/bam/...31912/4854/100

There is also a little screen that sits under the regulator, if it gets plugged it can affect fuel flow.

There is also a little ball that sits on top of the fuel pick up in the tank. It can stick and limit the fuel flow.

Also, the simplest is to dump out the fuel water separator. Leave it loose while you reprime the fuel system. That is the simplest and should be done first.

I have two cool fuel setups from my boat. I ditched and went A1000, boost reference regulators with my prochargers. I would be willing to sell you a pump if you want.

Does the 502 have a manual fuel pump?

I prefer electric fuel pumps by far to the manual ones.

You only ever have so much cranking with the batteries. Using the batt to just crank and fill the carb fuel bowl is a poor design in my view.

Having 2 pumps for 1 engine in parallel, set up and plumbed as a backup, is great and easy insurance for reliability.

For a twin engine setup, having a 3rd spare pump would prob be sufficient.

There is a saying in the military when dealing with explosives.

2 is 1, and 1 is none.

Talking about dets in C4 type applications, and reliability.

Well I ended up taking the boat to the shop. They found I needed a fuel pump, u-joints, 2 injectors, 8 spark plugs, bilge pump and found my compression was low(ish) with a few cylinders at 110psi and 30% leakage from intake valves meaning it'll need the top end refreshed.
I decided to ride out the rest of my boating season and have the heads redone next year. It runs amazing now, fresh ignition tune-up components, the 6 injectors were flow tested and cleaned, 2 replaced. It wasn't cheap in the slightest. But it's fixed.

Merc injectors or Amazon/ chinese ?

There is a lot of info from "BUP" on here about flow testing/cleaning injectors and the aftermath if you do a search

I would redo the compression/leak down test at end of season again. If U did a lot of cranking trying to figure things out that may effect the results? Also best to have engine warm from a days outing.