1999 Optimax 150 fuel question

KOBELKA2277

Cadet
Joined
May 23, 2008
Messages
17
Hello,
I have a 1999 mercury optimax 150 hp. I have been having trouble with it not idling. Very rough and stalls often. It runs above idle like a dream, smooth and powerful. I changed the plugs which looked fine, I changed the fuel filter with no results. The other day I did 2 things and the problem seemed solved. It sat and idled smooth for an hour. The two things that I did were check all fuel line joints for snugness and got air out of the fuel line which seemed trapped, the primer bulb seemed inflated with air not gas, which I corrected by removing the fuel line at the engine and then pumping the bulb for a while into a can to remove air. Then I noticed at the back of the engine there are 2 black rectangular stacks with fuel lines going to them and three electrical plugs on each one having # 1, 3 and 5 the other having 2,4 and 6. I assumed that these were something to do with the pressurized fuel delivery as they had air chucks on the tops of them as you would see on a tire to fill with air. I removed the black cover and depressed the center pin and a small gasp of pressurized air came out. On the one on the drivers side of the engine when depressed a squirt of gas came out. Then I started the engine on mid range rpm's and again depressed the centers of the air nozzles while running. The passenger side one blew out a continual mist of mostly air with a mist of fuel and made the engine run rough like starved for fuel. The drivers side nozzle blew out pure pressurized fuel hardly any air if any. Back I went to the passenger side nozzle pressing it letting air escape thinking fuel would eventually come but it didnt.
To make a long story short I put it back together and that is when it idled perfect for about an hour. Then I shut it off again and went back an hour later and right back to not idling again.
Today I changed the fuel lines and primer bulb and still idles rough.
Does anyone know if both the air nozzles on the tops of those 2 stacks when depressed should blow out fuel mist or pure fuel and what might be the cause.
Thanks in advance
kobelka
 

woody66912

Senior Chief Petty Officer
Joined
Jul 12, 2008
Messages
690
Re: 1999 Optimax 150 fuel question

you have a air side and fuel side on each fuel rail.if you have fuel in the air side you may one three things failed the tracker valve fuel pressure digphiam or air pressure diaphiam really the only way to diagnose this is with a duel set of gauges with a dump valve so you can dump one side at a time to check for air in fuel or fuel in air.lets hope you dont have a failed fuel pressure regulator diaphiam as this part is not replaceable you will have to replace the hole port side rail. these rails are flow checked by the E.P.A. so mercury has to follow there giude lines. iv'e replaced 4 of these so far this year at a cost of 800.00 some bucks parts only.
 

KOBELKA2277

Cadet
Joined
May 23, 2008
Messages
17
Re: 1999 Optimax 150 fuel question

Hi Woody,
Would any of those cause my engine to idle terrible but run strong and smooth thru the rest of the rpm range including full throttle.
Thanks
 

woody66912

Senior Chief Petty Officer
Joined
Jul 12, 2008
Messages
690
Re: 1999 Optimax 150 fuel question

absolutely this engine gets so little fuel at idle and is metered so lean that any extra amount will cause a rich condition at idle. if it's a very small pin hole then at wot it will burn the extra amount.
 

woody66912

Senior Chief Petty Officer
Joined
Jul 12, 2008
Messages
690
Re: 1999 Optimax 150 fuel question

if you think you can handel it remove side chaps and remove starboard side rail remove tracker vavle cover and inspect if ok then remove port side rail set on bench and remove lower cover this is fuel regulater be aware it's not easy to reinstall cover but at this point you got nothing to loose.
 
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