Mercruiser 5.0

[Dailyhazin88]

Hey I have a ? I have a 1989 stingray with the mercruiser 5.0 an the block mounted fuel pump is spraying fuel out of the vent on the back that leads up to the back of the carb.. Is my pump bad? What is this vent for?

 

[alldodge]

Yes you pump has ruptured the internal diaphragm.
The vent tells you the diaphragm has reptured

 

[Dailyhazin88]

I'm looking at getting the sierra marine replacement pump. What do you think?

 

[alldodge]

Sierra will work, not a fan but they work

 

[Dailyhazin88]

Tell me what u no about sierra? I've got another ? I recently just rebuilt my carb because I was getting gas in the crank case. Well I put the carb back on an it's still doing it I adjusted the float to factory specs. My ? Is could my fuel pump have been the problem all alone?

 

[alldodge]

My opinion
Sierra quality control is not the best. They build stuff in most cases like the OEM but not always exactly like the OEM. The stuff that won't meet OEM requirements are sold to aftermarket

 

[Dailyhazin88]

I got another ? I recently just rebuilt my carb because I was getting gas in the crank case. Well I put the carb back on an it's still doing it I adjusted the float to factory specs. My ? Is could my fuel pump have been the problem all alone?

 

[alldodge]

The fuel pressure might be to high. Anything above 6 psi can cause the issue. Being a 1989 you should have 2 gaskets and one plate between pump and block. The thick gasket and plate reduces the stroke, and thereby reducing the pressure the pump puts out

https://www.mercruiserparts.com/bam/subassembly/31835/1014/120

 

[Dailyhazin88]

Ok I didn't no that! Well I'm gonna order me a new pump an see what happens. Unfortunately I just changed the oil an it's completely ruined now so I get to change that again is there another brand fuel pump that you would recommend?

 

[alldodge]

I would buy this one
https://www.ebay.com/itm/Mercury-8M...338?_trksid=p2349526.m4383.l4275.c10#viTabs_0

 

[Dailyhazin88]

Hey thanks alot gonna order it tonight!

 

[76SeaRay]

Just remember that you need a line from the fuel pump vent to a carb inlet in case it ruptures again so that the leaking fuel doesn't spray into your bilge but is fed back into the carburetor for safety.

 

[Dailyhazin88]

I just replaced that ol girl with a brand new line. I hadn't never seen a vent line on a fuel pump like that thought it was kinda crazy but it makes sense. Do you concur with what dodge said on those fuel pumps? Just wanna get something good being as everything for a boat is high as a garraffis tale. I've seen babe reviews on sierra an the mercury quicksilver. Which I no how parts can be. Get a brand new part an it be bad...

 

[76SeaRay]

I don't know about the one alldodge recommended but older users on here generally know by experience. I did a lot of research for my scratch build 5.7L GM and went with a Carter Fuel Pump (manual marine pump not the auto version). It's very solid and high quality built. For critical components (like the fuel pump), its best to get high quality and reliability even if you have to pay more...

 

[Dailyhazin88]

Well I agree 100% on that. You get what u pay for. An being the family an I are gonna be on this boat when I get done. I sure don't wanna be stranded cause of a cheap fuel pump...

 

[Searay205]

many times when a fuel pump fails (engine driven) like yours it will also leak fuel into the crankcase. remember the fuel pump is driven by a lever driven by the camshaft so if diaphragm fails gas goes everywhere. Change your oil. the vent should be tubed to carb so it floods carb out and stalls engine when it starts to leak and boat don't go boom

 

[Dailyhazin88]

Hahahaha that's a good way to put it.. well when I fired the boat up last week when I was running it I noticed my oil pressure was going down so I shut the engine off immediately. So my first thought was the carb because it's old an I didn't no about the age of the internals. So I rebuilt it an put everything at factory specs an changed the oil. Well today I go an fire it up an with the new vent line from fuel pump to carb when it fired up I noticed gas coming from that vent from the pump an I wasn't sure so I ran it maybe another min an she was flooded. Pulled the dipstick an of course it had gas in it again brand new oil. So I was kinda frustrated about that but oh well. I'm gonna get me a pump an change that oil again.....

 

[Scott Danforth]

Original fuel pump is a carter. Not only less money than the sierra junk, its not sierra junk