Mercruiser Fuel Pump Old vs New Design

[runninfarmer]

I recently purchased a boat with a mid 80's 2.5L mercruiser. The previous owner says it needs a new fuel pump. I could rebuild it or replace it. I looked on boats.net for parts and there's an old design and new design listed here: http://www.boats.net/parts/search/Merc/Mercruiser/1985/01209005/parts.html. What is the difference between the two designs? Should I buy the new design if I decide to replace the whole pump? Thanks for the info and help!

 

[SDSeville]

The site didn't come up for me. Take yours off (s/b only 2 bolts and the hoses) and compare to the pictures. ...or better yet, rebuild yours if a kit is available.

 

[alldodge]

These links should work
Old Design http://www.mercruiserparts.com/Show...0&bdesc=FUEL+PUMP+AND+CARBURETOR+(OLD+DESIGN)

New design http://www.mercruiserparts.com/Show...0&bdesc=FUEL+PUMP+AND+CARBURETOR+(NEW+DESIGN)

 

[runninfarmer]

Thanks for the links. If mine is old design, do I need to stick with the old design? Are the two designs interchangeable? If so, would the new design be better, dependability-wise? I think I've found rebuild kits for the old so can I always just do that to save money.

 

[Fishermark]

I rebuilt my old pump - it was easy to do. The kit part number is 49089. But if you want to buy a new pump, I am pretty sure either one works with no problems.

 

[alldodge]

Thanks for the links. If mine is old design, do I need to stick with the old design? Are the two designs interchangeable? If so, would the new design be better, dependability-wise? I think I've found rebuild kits for the old so can I always just do that to save money.

Didn't answer the question because I would be guessing, sure was hoping some of the experts could advise but looks like no one showed up. I'll send a PM to a few I think can help, hopefully they can come in and advise

 

[Bondo]

But if you want to buy a new pump, I am pretty sure either one works with no problems.

Ayuh,.... I have to agree,.... Ya might run into issues with fittin's, 'n the clocking of 'em,....

 

[Fun Times]

Ya might run into issues with fittin's, 'n the clocking of 'em,....

Personally I'd try to stay with what you had if it seemed to work without issues due to there's a low and high volume fuel flow fuel pump... Plus from I could find, some of the older modeled "newer designed" high flow pumps seemed to have heat issues causing vapor lock which required Merc to come up with a water cool fuel line kit which is know longer available. < That may have been resolved though with the later part number 8M0073435.
http://www.ebay.com/itm/MERCRUISER-WATER-COOL-FUEL-LINE-KIT-NLA-PART-NUMBER-32-17870A2-/150996829007
http://www.boatfix.com/merc/Bullet/87/87_12.pdf

Though it's not accessible online, In 1986 Merc has a service bulletin titled High volume fuel pump to fit 120/140/2.5/3.0 liter sterndrives.

So it appears it would fit, just not sure what the bulletin says or if you need a kit to make the fuel lines work with it or not. Should you decide to give the new one a go, you may need to have a Merc dealer check on service bulletin # 1986-11 B before ordering.

Let us know what you decide, good luck.

 

[runninfarmer]

Thanks everyone for the info. I've mainly worked with outboards so this is my first inboard to play with. Sounding like getting a rebuild kit for the old design might be the best option.

 

[fishrdan]

If you have an old style pump, stick with the old style pump...

I tired a new style pump on my 140HP Mercruiser and the gasket barely covered the block cutout. And while the engine did run with the pump to some degree I had issues with fuel starvation and other weird behavior. I was under the assumption that the pump arm was hitting the cam in a different position and either not getting enough stroke or too much, so I replaced it with the correct old style pump and all of the weird problems went away.......

Airtex makes that pump, so does Carter, if you can find one. Rebuilding as fishermark is possible, if you can find the kit. I couldn't when I was having fuel pump problems and scrounged up a new Carter. One thing about rebuilding the pump, make sure all the steel parts inside the pump are not rusted due to water in the fuel. Rusted parts could cause an over pressure situation...

Fishermark did the rebuild kit come with all the internals (IE: metal parts) or just the gaskets and rubber parts?

 

[Fishermark]

I don't believe it came with any of the metal parts - only rubber. My pump was in really bad shape and had been sitting for a long time. But I was able to get it apart and cleaned up. The metal pieces I was able to re-use. It's been a year or two ago... so my memory is getting fuzzy on the specifics. The good news is I always take photos since my memory is bad. That helps me put things back together!