1991 ?? Mercury Force - Fuel streaming from prop while priming

[Theoutdoorsman]

?? 1991 ?? (Serial Number is no longer legible)
Mercury Force 70 hp history:

I acquired this outboard recently, and I'm trying to get it running properly. (Service Manual on hand.) It was terribly difficult to get running initially. Found the timing to be off a little bit. Reset timing, and she ran/started much smoother. Then the fuel bulb was becoming mushy at an idle, while underway, and she'd stall out if/when idling for any length of time. Replaced the squeeze bulb, and the problem persisted. I then rebuilt the fuel pump. Now the motor is flooding, and a stream of fuel will exit the prop area when the squeeze bulb is used to prime the system. I removed the carb, and made certain the float was level with the carb body, just to rule out a stuck float, but the problem persists. Is it possible I've rebuilt the fuel pump incorrectly, or could it be the diaphram in the primer solenoid is the culprit? Thanks for any and all responses in advance.

 

[Theoutdoorsman]

I've since pinched off both lines coming from the fuel primer solenoid, and fuel will still come out of the prop when squeezing the bulb. I'm at a loss here ...

 

[racerone]

I would say you need to look at the fuel pump.----From a 1000 miles away I think there is a ruptured diaphragm.----Easy fix here.

 

[Theoutdoorsman]

I'll tear it down again, and see what it looks like.

 

[Theoutdoorsman]

I would say you need to look at the fuel pump.----From a 1000 miles away I think there is a ruptured diaphragm.----Easy fix here.

You were 100% correct! Not just one diaphragm, but both had ruptured. Now .... why? The diaphragm's had ruptured where they met the housing surfaces. I can only assume I over-torqued the bolts when installing. Would you say that's a fair assessment?

For clarification, both diaphrams install to the outsides of the pump housing. Not behind the gaskets .... correct? Both failed diaphragm's were installed brand new (sierra part # 18-7817)

 

[WinnerCougar74]

I had a 1 month old diaphragm rip on me. I was told a cough or backfire can cause it. Fortunately I bought a lot of them knowing that they are a weak point on these motors. I also had fuel running down the exhaust leg. I though it was a float needle that was stuck open but I was wrong. It was the ripped diaphragm. I am glad they are easy to replace. I only use REC gas so it wasn't the ethanol that ruined it. I wish there was a better fuel pump out there.

 

[puffitu]

Yup over torquing will actually cause them to rupture; speaking from personal experience

 

[jerryjerry05]

You can double up the diaphragms if worried about rupture.
Bought a boat with twin 88/85hp Forces.
BOTH motors had double diaphragms.
The old owner said he was an avid offshore fisherman, as much as 80-100 mi off shore. He wanted to make sure the pumps didn't fail????

 

[WinnerCougar74]

Really great suggestion I'll be doing that.