Merc 470 Fuel Pump Problem?

[Eric 3.7LX Alpha 1]

If your definitely getting a new pump... I'd be tearing my existing one apart. Check it out, if it is the diaphragm that's torn, Terry had a link to a diaphragm kit for one of the pumps that fit the 470, as an option....

And IF I was stuck with the new pump cause gas went thru it... and they don't take it back......

I think I'd break it apart and compare the two diaphragms side by side.... maybe the good one may find a new home in the one that fits the engine

 

[SDSeville]

If your definitely getting a new pump... I'd be tearing my existing one apart. Check it out, if it is the diaphragm that's torn, Terry had a link to a diaphragm kit for one of the pumps that fit the 470, as an option.... And IF I was stuck with the new pump cause gas went thru it... and they don't take it back...... I think I'd break it apart and compare the two diaphragms side by side....

I think that diaphragm kit was only for the older model pump. I will check again. Funny you mention comparing the diaphragms. I just came inside from removing the new pump and was thinking the same thing - wondering whether I could just put the new diaphragm in the old pump. I wouldn't care that I spent $200 on a diaphragm. I just want it to work.

 

[SDSeville]

Just took the old pump apart as Eric suggested. The diaphragm actually looks OK. I got a new pump because gas was going up the overflow hose and into the carb. Here are some pics of the inside of my pump.

http://i859.photobucket.com/albums/ab160/GJR3594/photo1-2.jpg

 

[SDSeville]

Does this look bad?

http://i859.photobucket.com/albums/ab160/GJR3594/photo2-2.jpg

 

[bfjou812]

It looks like the rubber is dry rotted and cracked around the metal part of the diaphragm to me. This is strange I replaced the pump on my 470 and had none of this problem with wrong pump ,etc. I guess I got lucky? Hope you get it straightened out soon .

 

[ktbarrentine]

Yep.... my failed diaphram looked identical to yours. Good ol' ethanol fuel!!!

 

[stonyloam]

You know, I can't believe that diaphragm is anything special. Bet they used them in many pumps, just need to match the size. Is there a number stamped on it?
Found this on breezeworks, I knew I read it somewhere. Try the spacer 27-43186 and check the pressure, if 3-6 should be OK. http://www.breezeworks.net/cgi-bin/M...urnPage=Search The one in the photo looks pretty thick, so if the new ones are thiner, I guess ou couls stack a couple. Good luck.

 

[SDSeville]

There are no numbers on the front. Do you know how to remove the diaphragm from the pump so I can check the back? I can't figure it out.

 

[stonyloam]

Can't help you there.

 

[SDSeville]

The new pump (8M0073435) seems to work great. Ran great on muffs for about 20 min with no flooding. Will try her on the water this weekend.

I noticed a couple differences on the new pump (8M0073435) compared to the 1st one (861676A1) I got.
1. I could move the arm down by hand if I pushed real hard. I could not get the arm on the 1st pump to budge.
2. The thick gasket I got with the new pump is made out of what appears to be wood instead of cork (like the 27-43186 I received with the 1st pump). When I tightened the 1st pump to 20 ft lbs, the cork gasket compressed quite a bit and was no longer the 3/16" it was originally. The new gasket did not compress at all.

Thanks for the help everyone!!

 

[Eric 3.7LX Alpha 1]

Nice!
Did you get stuck with the wrong pump or they take it back?

 

[SDSeville]

Nice!
Did you get stuck with the wrong pump or they take it back?

I called Mercruiser before I took the pump back. They approved the return and gave me a reference number to give the shop. With the reference number, the guy at the shop gave me no problems at all. He took the old one and ordered the new one. He still didn't really believe the pump might be bad, but didn't care since Mercruiser approved it.

 

[ktbarrentine]

Duplicate (deleted post)

 

[stonyloam]

Hey SD, glad it worked out, you are off by one 0 in your number, should be 8M0073435 FYI. go enjoy the summer!

 

[SDSeville]

Hey SD, glad it worked out, you are off by one 0 in your number, should be 8M0073435 FYI. go enjoy the summer!

Ooops. Thanks Terry. I edited the number above.

 

[SDSeville]

Well, I got caught up with work and was finally going to get the boat out yesterday. I was warming her up at home just to make sure everything was still running smooth and I noticed that she was idling very rough. Seemed to run fairly smooth above about 1750 RPMs, but ran real rich at anything lower. Would barely stay running at 1500 and would die about 15 seconds after I dropped her down to about 1,000 RPMs. I checked the fuel pressure and it ran at 11-12 PSI (hadn't done with the new pump yet because I had borrowed the tester from AZ last time). Ran much better than when I had the other pump with 15 PSI, but not acceptable.

I really don't understand why things like this are not simply plug n play. Going to get a low pressure electric pump in the next couple days and move on. I need to get this thing running right for a week long trip to Lake Mohave in 11 days.

 

[olazabel]

plenty of carter pumps on ebay that are an exact match. just have to read the descriptions carefully

 

[SDSeville]

I haven't seen any Carters with the same straight arm as the original. The electronic pump seems easy enough. Local Mercruiser dealer has conversion kit with the pump, oil pressure switch, and plate for where the old pump was for half the cost of the mechanical pump. . Although I could probably get that one wrong also.

 

[stonyloam]

Hey SD, does the kit have a fuel pump relay? If not you probably should use one. Let us know the brand and how it works out.

 

[SDSeville]

Hey SD, does the kit have a fuel pump relay? If not you probably should use one. Let us know the brand and how it works out.

Thanks for the suggestion Terry. The kit does not have a relay. I will be sure to purchase one. The shop says the pump is 3 to 7 PSI. Does that sound ok? I thought it was supposed to be 3 to 6.