470 MCM Mercruiser fuel pump?

Status
Not open for further replies.

IceWater

Seaman
Joined
May 30, 2010
Messages
60
Took the boat out on Saturday and it would stall during both acceleration and deceleration it would also idle rough and die when trolling. Then it would work fine for 10 minutes. When I got home I checked the fuel filter and it was dry. I'm thinking I need a new fuel pump?
My next question is how difficult is it to replace the manual fuel pump with an electric?
 

Bondo

Moderator
Staff member
Joined
Apr 17, 2002
Messages
70,465
Re: 470 MCM Mercruiser fuel pump?

Ayuh,... I'd sooner think you have a restriction, Upstream from there....
 

IceWater

Seaman
Joined
May 30, 2010
Messages
60
Re: 470 MCM Mercruiser fuel pump?

You thinking in the fuel tank? I'll check that, but shouldn't there have been fuel in the filter? It shouldn't be draining back past the pump? The return line is on the other side of the carb.
 

EddiePetty

Lieutenant Junior Grade
Joined
Aug 25, 2008
Messages
1,008
Re: 470 MCM Mercruiser fuel pump?

You thinking in the fuel tank? I'll check that, but shouldn't there have been fuel in the filter? It shouldn't be draining back past the pump? The return line is on the other side of the carb.

Okay, ICEWATER......I'll bite. What kinda carb'ed 3.7 has "The return line on the other side"?

If you would disconnect the flexible fuel line on the suction side of the mechanical and splice in a temporary fuel supply, you could isolate your problem to correct side of the pump.

I gotta agree with the 'ol BondO.
 

half_wolf

Recruit
Joined
Jul 5, 2010
Messages
4
Re: 470 MCM Mercruiser fuel pump?

On top of that... the mechanical fuel pump is not hard to change and not that expensive.. I got a new sierra marine replacement on ebay for about $70.00. For my 470. I would just stick with the mechanical.
 

IceWater

Seaman
Joined
May 30, 2010
Messages
60
Re: 470 MCM Mercruiser fuel pump?

When I look at me carn there is a metal line from the fuel pump to the carb which unbolts to reveal the fuel filter. Directly across from the fuel filter there is a flexible rubber hose that goes back to the fuel filter. Is that rubber hose not a return line? Perhaps I'm confusing the fuel return system on my C15 CAT with a gasoline system?
 

zbnutcase

Commander
Joined
Sep 19, 2009
Messages
2,055
Re: 470 MCM Mercruiser fuel pump?

No not a return line, its there in case of pump diaphram failure to direct fuel to dump into carb, not the bilge
 

IceWater

Seaman
Joined
May 30, 2010
Messages
60
Re: 470 MCM Mercruiser fuel pump?

Ok, that makes sense. I thought it was a return line because I have only seen a second line used as a return line.

I'll run the fuel pump tests next time home Ande take it from there. If I do go with a new fuel pump I'll probably just stick with a manual' but I will add a water separater.
 

EddiePetty

Lieutenant Junior Grade
Joined
Aug 25, 2008
Messages
1,008
Re: 470 MCM Mercruiser fuel pump?

When I look at me carn there is a metal line from the fuel pump to the carb which unbolts to reveal the fuel filter.

IceWater.....you ARE aware that there is another fuel filter inside that little metal can on top of your fuel pump...aren't ya'?
 

IceWater

Seaman
Joined
May 30, 2010
Messages
60
Re: 470 MCM Mercruiser fuel pump?

Eddie Petty,

I didn't check the filter on the pump, regardless, my original question was whether or not there should be fuel in the filter in the carb? I don't know much about boats at all, that's why I ask. I know a lot about trucks and a lot about 1960's Fords , but boats are very different.
No one has answered whether or not there should have durl in the carb filter? I think there should; a boat isn't that different than a 1967 Cougar.
 

Bt Doctur

Supreme Mariner
Joined
Aug 29, 2004
Messages
19,093
Re: 470 MCM Mercruiser fuel pump?

There was a TSB saying to remove the carb filter because of restriction.With a filter on the pump and/or a fuel/water sep filter ,it`s all you need.
 

IceWater

Seaman
Joined
May 30, 2010
Messages
60
Re: 470 MCM Mercruiser fuel pump?

Please excuse the spelling, I'm using my BlackBerry and it has a mind of it's own. Durl should be fuel and carn should be carb.
 

nola mike

Vice Admiral
Joined
Apr 22, 2009
Messages
5,023
Re: 470 MCM Mercruiser fuel pump?

Eddie Petty,

I didn't check the filter on the pump, regardless, my original question was whether or not there should be fuel in the filter in the carb?.

Yes, there should be fuel in the filter. And in the carb. The answers were that there are other things to check before assuming that the pump is the problem.
 

IceWater

Seaman
Joined
May 30, 2010
Messages
60
Re: 470 MCM Mercruiser fuel pump?

But, isn't the lack of fuel in the carb filter a sign that the fuel is leaking back past the fuel pump? Where else can it go? No signs of leaking.
The most common answer on replacing the manual pump with an electric - provided the fuel pump needs replacing - is to just replace it with a manual' so that's what I'll do.
 

nola mike

Vice Admiral
Joined
Apr 22, 2009
Messages
5,023
Re: 470 MCM Mercruiser fuel pump?

But, isn't the lack of fuel in the carb filter a sign that the fuel is leaking back past the fuel pump? Where else can it go? No signs of leaking.
Not sure what you mean. No fuel at the carb only means you aren't getting fuel to the carb. For any reason, including a fuel pump. Or empty gas tank. Or clogged upstream filter. Or...whatever.

The most common answer on replacing the manual pump with an electric - provided the fuel pump needs replacing - is to just replace it with a manual' so that's what I'll do.
Ok. Then, if that doesn't work, you can troubleshoot your problem...
 

IceWater

Seaman
Joined
May 30, 2010
Messages
60
Re: 470 MCM Mercruiser fuel pump?

Not doing anything until I jbow what the problem is, that's why ask.
I didn't have time to go through the manual and do the fuel pump test, but I was hoping to get a few clues from the few things I did do before I had to hit the road.
 

IceWater

Seaman
Joined
May 30, 2010
Messages
60
Re: 470 MCM Mercruiser fuel pump?

Finally got a few minutes today to run a test on the fuel pump and guess what? I need a new fuel pump.

First thing I did was to remove and inspect the fuel filter in the fuel pump...not good...

IMG_0780.jpg


IMG_0782.jpg


After that I removed the fuel line from the tank to the pump; it's worse, yet wasn't leaking..yet.

IMG_0788.jpg


IMG_0789.jpg


IMG_0791.jpg


I'm sure this was the original fuel line.

IMG_0792.jpg
 

IceWater

Seaman
Joined
May 30, 2010
Messages
60
Re: 470 MCM Mercruiser fuel pump?

Next I tackled the fuel pump diagnostic test outlined in this:

IMG_0778.jpg


The first test I did, with the new fuel line, was using a jerry can for a gasoline supply and a second jerry can to measure the out put...there was next to none, a slow, inconsistent, small stream of fuel after about 7 seconds of the engine turning over. She's toast. Clearly the engine was using it's own vacuum to pull fuel through the line. I should have had to row home. Dumb luck that I didn't.

IMG_0795.jpg


To be sure the pump was beyond hope, I ran another test, this time with the boat fuel tank for supply and also with the fuel pump filter removed. Same result.

IMG_0796.jpg



I am ordering the parts from I-Boats, the least I can do after they provided this incredible forum which has saved me thousands in repairs. They are also much cheaper than purchasing a fuel pump here in town. The local Mercruiser dealer wants $450 plus taxes which are another 10% on top! Welcome to Canada, eh? I-Boats want $116 plus shipping and exchange, so maybe $150 Canadian delivered to my door. Pretty simple math.
 

IceWater

Seaman
Joined
May 30, 2010
Messages
60
Re: 470 MCM Mercruiser fuel pump?

Took about a week, but the new fuel pump arrived - thank you iboats! - and then it took another week before I got home to put it on. There were a couple of small snags, the biggest being that the fuel intake fitting from the old pump would not fit into the new pump, just wasn't going to happen, So I took part of the old pump and put it onto the new pump: Success!

New Pump.
IMG_1067.jpg


Out put fitting. Clearly it has been blocked off for a very long time, but not the most significant problem.
IMG_1069.jpg


This was the big problem with the fuel pump. it is obvious that fuel has been leaking past the diaphragm for sometime. There is far too much corrosion in that spring for it to be a recent leak.
IMG_1083.jpg


Installed.
IMG_1074.jpg


Well, that is one problem fixed, now to replace the oil lines from the trim pump to the gimbal housing; leaking like a sieve. Oh, joy!
 
Status
Not open for further replies.
Top