Belt driven raw water fuel pump assembly
 

Greetings all, looks like I’m into break out thousands again territory. I thought I had an oil leak but it seems to be coming from the belt driven fuel pump which I understand has gear lube inside with shaft bearings that go bad.

has anyone had any luck with the aftermarket replacements which are in the 200-300 range or is this a only buy Mercruiser 1,100 part?

has anyone had these pumps rebuild successfully?

Thanks
Duane

I know a guy that’s running the Amazon ones and not having any issues at all. I’m sure others will chime in.

https://a.co/d/09MU3B4K

one for the pro column!! Thanks.

I would definitely do some homework on this.

You don't have much to lose by trying one of those out. The real concern is the fuel pump. I keep buying the merc overpriced pumps, that start to leak within a year or 2 and they trash the seal on the sea pumps. I tear the fuel pumps down and cannot find anywhere they are leaking.

Love the translations
but that store has all kinds of things

these pumps can be rebuilt. I have done a few with good results. I have changed the bearings out to the 2RS style (double rubber sealed) that way i removed the rubber seal on the inside section of the bearings for oil to get inside and still have another seal on the outside of the bearing to help keep things inside the pump assembly. Sort of a double seal on each end of the shaft.

Helmwurst, I cant remember what the brand of pump it was but i have used a regular automotive fuel pump before...the only thing that different is how it leaks the fuel out in case of a diaphragm rupture. The standard auto version just has a hole to leak onto the ground since they are out in the open air. On a boat i have taken the pump body apart and drilled and taped the hole to install a nipple and ran a small 1/8" fuel line up tot he carb to dump into the engine in case of rupture...thats the way the old merc style pumps were done anyway...

^^^^ Wally that would be great if you remember what pump you used. I cannot believe Holley does not make one. The pumps I see on Amazon have a roll pin that holds the arm in place. I would NOT recommend one of those. Even the Carter's marine fuel pump has those, and we put those on a friend's boat last year and one failed in the first 2 hours. Wore out the roll pin and the hole to the point that the arm fell off when I removed the pump. The other engine pump was starting to show wear in the same area.
If you can, due you remember the part number of the seals that you used in the sea pumps? I could not find a cross reference to the factory seals and I like the idea of using a 2RS seal.

I honestly don't remember what fuel pump i used :( ...that was like 25yrs ago now....i want to say it was an Edelbrock pump i used but it may have been a holley just the same...sorry


https://cimg2.ibsrv.net/gimg/www.off...e805ef70e8.jpg
Old style pump
https://cimg3.ibsrv.net/gimg/www.off...8083c8e9a7.jpg
bearings for old style pump
https://cimg4.ibsrv.net/gimg/www.off...e4c83a418f.jpg
Inner seal taken out
https://cimg5.ibsrv.net/gimg/www.off...42578bf304.jpg
Seals for old style pump
https://cimg1.ibsrv.net/gimg/www.off...10e93d1232.jpg
Fuel pump style seawater pump
https://cimg2.ibsrv.net/gimg/www.off...45215843bc.jpg
Dust cap removed
https://cimg3.ibsrv.net/gimg/www.off...1adcdfe5e5.jpg
must remove retaining ring
https://cimg4.ibsrv.net/gimg/www.off...8658218f81.jpg
retaining ring removed
https://cimg5.ibsrv.net/gimg/www.off...5b073d82fc.jpg
Shaft assembly removed
https://cimg6.ibsrv.net/gimg/www.off...f16a36f46d.jpg
Shaft assembly taken apart
https://cimg7.ibsrv.net/gimg/www.off...e52ef31ac4.jpg
Drilled and tapped a drain plug for easier maint.


The bearings for the pumps with the fuel pumps on them....... i think are the same size as the non fuel pump style pumps. And i know those are the 6204 bearings cause i have a pic of them. I know those are 20mm ID for the shaft, 47mm OD and they have a 14mm Width
So i would take the pump apart and measure the old ones to be sure. Then get them in a 2RS version and just take out one of the seals on the inside where it will be filled with oil. You may need to clean out the bearing grease in there just so it doesn't cross contaminate the oil.
The actual seals i don't know what the part numbers are for those. I do have the part numbers for the old style pumps....there's 3 of them. the two small ones are a 7450 and the one large dust cap behind the pulley is a 7690
I really suck at taking pics consistently. I have a habit that when i start a project i just plow right through it without stopping to take pics and if i do i usually missed like 10 steps along the way! :D

Have you ever changed the gear lube?? It gets fuel diluted and over pressurizes.
The sea pump rebuild kits are on ebay, but you need a hydrailic press do it.

I already rebuilt my sea pumps and pre-lubed the bearings with this stuff that oil will never penetrate. This stuff is used on Dyno bearings. My pumps are also drilled and tapped for the relief tubes. My main issue is to find a fuel pump that will work w/o leaking into the oil reservoir. The lube is for the fuel pump arm bushing.

I know someone that has been running 2-$150 ebay pumps with no issues. I keep a spare eBay pump on my shelf for just incase.

Im fixing to buy a spare and keep it in the boat.

Thank you all for the knowledge and input especially the detailed break down with pictures, learning is occurring!!!!!

I honestly don't remember what fuel pump i used https://www.offshoreonly.com/forums/...lies/frown.gif ...that was like 25yrs ago now....i want to say it was an Edelbrock pump i used but it may have been a holley just the same...sorry

Walley, thanks for that. If i could find an automotive pump with the right arm to mount on the sea pumps, I would do it and modify it to vent to the flame arrestor. In addition to all of that, the Holley's have a larger in/out port which I would also like to have.

This is a new to me boat. I have not changed the lube, I just noticed after my last outing that lube had to be coming from that location. The over pressure would make sense. So if the pump isn’t squeaking it may not need a rebuild just a reseal and fresh lube?

If fuel is leaking into the oil chamber then its only a matter of time before it all goes south when there's no more oil in there to act as a lubricant. You may have gotten lucky and caught it early...so it may be just a quick re-seal and a new fuel pump and back in business...or you may get extra lucky and its actually just a bad seal so you can do seals and oil change and back on the water...just depends on whats going on.

Ok so it needs taken apart and replace all the seals at a minimum if it doesnt need new bearings and a new shaft. I think I’m understanding that part. Why would the fuel pump need to be replaced? Is that the seal thats failing and leaking into the oil chamber?

The fuel pump is causing the issue. It is leaking fuel into the oil chamber and causing the sea pump seals to fail.

Yes if you have the style of fuel pump that can be taken apart, you will see once its open that the arm of the fuel pump that rides on the cam in the seawater pump is connected to the diaphragm that pumps the fuel to the engine. Once that diaphragm ruptures it starts leaking....only problem is the orientation of the fuel pump on top of the sea water pump makes it leak into the chamber where the oil is for lubrication. So the entire oil chamber has to fill up with fuel before it will start to travel up that "overflow" tube up to the intake/air filter. Thats assuming all the seals hold up and don't leak before it gets up the the top.
I'd say probably 80% of the time the sea water pumps are shot cause the owners didn't know it was happening until its seizing the bearings from lack of lubrication :(
Others get lucky and catch it before any damage happens and are able to rebuild them for cheap :)

https://cimg4.ibsrv.net/gimg/www.off...dd472e3300.gif

https://cimg1.ibsrv.net/gimg/www.off...ed583c193.jpeg

I have rebuilt the three of mine with no problems i used an alternator bearing from a 70s dodge alternator parts store cost 7 bucks! seals are 6 bucks and it takes longer to get it off than to rebuild it! i will figure out the part numbers an repost!

A little update on the mechanical pumps. I spoke to a friend who I consider one of the best performance boat mechanics. The stuff he works on is above my pay grade, so I go to him when I am frustrated and cannot get a straight answer. I also make an appointment to not interrupt his day. "All fuel pumps leak. If they are on the block, they leak into the engine oil. If it is mounted to the sea pump, it leaks into the sea pump oil" "You change your engine oil every few hours or season, it gets rid of the fuel that leaked into it. Change the sea pump oil at least each season or more often if needed. With the pump being mounted down it leaks more. Running the merc pumps, put a drain hole in it to make it easy." "Or go electric. Solves the leaking fuel into the reservoir issue."
For me, I may just run the mechanicals one more year and figure out the electric conversion for next season.

May or May not help
I am sure electric pumps now are managed in a similar way in non electronic engines
But back in. 1990 my 1988 omc block took a powder
industry had switched to electric pumps
they had a simple setup
That let the pump prime for a few seconds with key on
Then it would not cone back on until alt was producing a charge
I could see you with a simple relay set up

i did have to install a fuel cooler in the cooling water loop
as that pump got fuel very hot...so much so it boiled a time or 2
maybe to much flashback
but hey i just thought out loud

https://cimg9.ibsrv.net/gimg/www.off...83db4b2ce1.jpg
If you guys want to run an electric fuel pump its actually quite easy. I drew this up for another member years ago...not sure where i found the part numbers for the oil pressure sensor and the mating connector from (off the internet obviously) but i know this works.
you don't need to have the push button (prime) option or the led indicator if you don't want to but they found it useful. And if you wanted to take it one step farther just install a switch on any one of the legs going to the relay and have a security feature where the pumps will never start up unless the switch is in the on/run position for the pumps to work. The boat will start and run off of what ever fuel is left in the carb bowls but after they run out she's dead in the water :D

Wally thanks for that schematic. I did not realize the oil pressure switch was 3 wire. That makes a big difference in things. And I like the idea of a primer button!

Depends on what its made for.....most are two wire though. ;)

SMP still makes the oil pressure switch. Your schematic was exactly what I needed. I just wanted a way to fill the bowls before cranking and that solves that. I could even put a switch in the bilge area and wire in the security feature. My routine is to check the oil and other fluids before the first start up. Hit the primer switch for 5 seconds after the last check, hop in the seat and hit the key. These things fire off cold with a single full throttle prime anyway.