2006 Mercury Optimax 150

[Younce]

New here, been looking for a good forum and finally joined. I have a 2006 Optimax 150 with a fuel problem. About a month ago after we were gone for over a month on a trip out west I went out to the Marina to check on boat , tried to start , turned over good then seems to slow a bit, first thought was fuel problem , I didnt have many tools on me so I just tried a couple of things one which was unscrew the filter and check to see if it was dirty ( just looking for anything) seemed very clean , then read a few forums and determined the bat was low so I charged it for several hours , finally cranked . I think when I first cranked I might have flooded but non the less have taken the boat out a couple of times, did notice it ran about 2 mph slower and a few rpms less than previous , . let it set again for a week and went out this Sat ( Oct 6) tried to crank turned over good but wouldn't crank, checked spark on one plug , had spark, checked what I assume is valve for fuel on top of port side fuel rail had zero pressure after cranking , checked the other valve below on the same rail had pressure ( not sure how much with no gauge on hand did spray a bit of moisture out but tried a few more times no moisture but had pressure, never had any pressure on top valve ( I assume fuel valve) disconnected line to low pressure pump and was pumping good , High pressure pump makes a sound like its running at least it is vibrating, also I removed the brass drain on the vst and had clean fuel run out. I suspect a bad high pressure pump .Wondering if any of you have bought any of the after market pumps you find on amazon other sites, dont mind spending whatever on this but like anyone else I wouldnt mind saving a bit but only if it is a reliable pump. Thanks Darin

 

[Chris1956]

Gee Darin, Those motors are pretty complex, with 2 electric fuel pumps, a mechanical fuel pump an air compressor and all the electronics.

It could very well be one of the fuel pumps, but they are pricey. I would recommend a through diagnosis by someone with the twin pressure gauge system and diagnostic computer. I think it will save money in the long run.

 

[Younce]

been wrenching on about everything since around 1973 but this thing is complex and you are right need diagnosis . I did call a guy here in SC that will come out to boat, $75.00 for visit , $100.00 hour for any work done and was thinking about letting him come ,A couple of things he said kinda makes me wonder, I told him what i had done as far as checking pressure on fuel and air , I said I checked the fuel pressure on top of rail ( port side) and then checked the schrader valve further down on the same side and he alluded to there not being a valve there , forgot his exact words but he said air was on the other side, well this valve in question will build up pressure each and every time I run starter and let out air so I am a bit confused but am convinced it is an air valve. also he said he might not be able to tell if the pump is bad using his equipment which I understand from some of my past experience on autos which would lead to a possible lengthy trial and error . Again I dont mind getting a better opinion but I can do the same thing as far as determining if pump is bad . I am thinking before I get him out I will try on my own to determine if the high pressure pump is ok. Ive already determined the low pressure pump is working , putting out a good steady stream , as is the other pump while cranking engine, the problem is somewhere between those pumps and the final output of the high pressure pump. Still not totally schooled on this motor but can at least check a few things that are obvious. Still wondering if I need a pump are these after market pumps ok,

 

[Younce]

I removed the vst, both pumps seem to be working well ( strong flow) vst was really clean, no trash anywhere screen on high pressure pump clean as well . When I removed the 7 screws that hold the top to the bottom of the vst the screws were not very tight , barely had to turn them to remove . All this and no pressure at fuel rails, is there a pressure reg that could be clogged between high pressure pump and fuel rail?

 

[schematic]

Pinch off the fuel return line and check if fuel pressure returns while cranking.
also check the sleeve seal on the outlet of the high pressure pump....

 

[Younce]

Thanks, will do this evening.

 

[Younce]

schematic, I worked late so Didn't get to reinstall vst but did put it back together, As far as the outlet seal on the high pressure pump , I suspect you are talking about the small rubber one that fits on the pump outlet tube and not the larger donut ( aprox 1 1/2 inch diameter) . If it is the small seal then gotta say it is pretty bad shape, hard and cracked . Not sure what it was suppose to originally look like but this one is tubular on the end actually going into the small exit tube of the vst housing and the other end is sorta conformed to the shape of the pump , kinda mushroomed so to speak . The pics ive seen of this seal are all just a small tube aprox 3/4 inch long with perhaps a 1/4 or 5/16 inside diameter and maybe 1/2 or a bit less outside diameter. I know I have to get a new seal but still want to install and try what pinching the return tube If I dont find a seal today. Now , just to clear up something , when I mentioned to the mobile mechanic I spoke to on the phone that I had checked for fuel pressure and air pressure ( without gauge) he responded that the port side schrader valve was for air, I explained to him there was a schrader valve sticking strait up on the top of the portside fuel rail and about halfway down the same fuel rail there was another schrader valve pointing in a rear direction. He seemed to disagree, but i promise it is there and there is no schrader valve on the starboard side fuel rail. After looking on Manualslib I see that they show a pic of a fuel pressure port on the starboard side and it is a schrader valve and they show an air pressure port on the top of the port side fuel rail but no other schrader valve below like I have. Now the reason I assume the valve on the top of the port side fuel rail is fuel ( and this is where I might be wrong), back when I first had starting issues a few weeks ago I had no tools with me on that day but I did remove the cap on the schrader valve at the top of the port side fuel rail and I am sure I got a spray of fuel , but after reading some other post , perhaps i got a spray of air with a bit of fuel and this whole time I have assumed this was a fuel valve, but the thing is when I crank the engine fr a bit , i get air coming out of the lower valve on the port side but get nothing on the top valve on the port side.

 

[schematic]

. If it is the small seal then gotta say it is pretty bad shape, hard and cracked . Not sure what it was suppose to originally look like but this one is tubular on the end actually going into the small exit tube of the vst housing and the other end is sorta conformed to the shape of the pump , kinda mushroomed so to speak

if that seal leaks, you may have low/no fuel pressure. Of course a bad pump or supportive wiring will also cause no fuel.
You need a repair manual and gauges to check properly. This is not a simple sytem..

 

[Younce]

Here is the seal from the high pressure pump. When I first pulled this I assumed this seal was normally shaped like this but after looking at several pics on various sites I realized this was not the way this seal is suppose to look. I believe what happened was the last person whom installed this , allowed it to slide down the pump outlet nozzle a bit too much and when they pressed the pump upward into the housing it went into the small cast tubular housing it is suppose to fit in just barely enough to seal but it was pressed against the top of the pump and it actually has marks where it conformed to the exact shape of the area it contacted on the top of the pump. I saw that the new factory seal is basically a short piece of tubing. I couldnt find a seal on Sat so I made one out of some fuel line. I cut it a bit longer than the what the factory allowing it to be pressed into the housing but not allowing it to slide down as this one did . It work perfect and now I have a running engine with a reading of 90 on fuel pressure and 80 on air.

 

[Younce]

BTW, I have to say I am not impressed with this motor as far as some of the engineering if you wanna call it that. First of I previously has the ole floppy belt which took out the alternator bolt so I installed a new belt and new tension spring but it still has a bit of a flop and I believe the problem is there is too much space between the alternator and the compressor pulleys and there should be an idler puller between.I have replaced belts, tensioners, water pumps etc..... on all sorts of autos and trucks and rarely have I seen a run as long as this especially with a small belt . Also I noticed several post concerning the tension spring and the broken boss on the top of the block , again this is pretty poor engineering . Several folks have had to try to tig weld a new boss on the block to remedy this but if mercury had just made this boss a bit thicker it probably would have not become an issue . The high pressure pump set up is a bit weird . As you know the pump is inside the vst and relies on the top and bottom half of the vst being screwed together with the aids of a rubber bushing at the bottom of the pump and also at the top ( larger seal where pump housing is squeezed into) along with the afore mentioned seal that simply fills in the gap of the pump discharge nozzle and the housing of the vst which leads up to a final brass nozzle where you attach the output fuel line for fuel delivery. I think they could have had the final fuel line attach directly to the pump , perhaps a longer nozzle end on the pump itself where it would exit the top of the vst with a seal replaceable right there from the outside and you could attach the fuel line there as well or perhaps an external high pressure pump that sets outside the vast housing , could be done and still perform. Still have some other gripes concerning this motor but these are some observations that come to mind . I have this motor running good now and will be selling it in the near future and getting a 4 stroke . Gotta say not too impressed with Mercury.