Merc 150 wont take fuel (UPDATE)!!!

[LubeDude]

I feel like Im beating a dead horse, but here goes again.<br /><br />This is an 87 150 V6, Ive just had a stator replaced and before this I rebuilt the carbs, new fuel lines and filters, new fuel, new plugs. Compesion 120#s all the way across. Engine has allways not wanted to take throttle from Idle and still will not. If you stab it, it runs beautifully, never misses a beat and will run all the way back down to when the boat falls off plane and then it will die if you do not put the boat in nutral. It ocationally will cough or sneeze every ten seconds or so when Idleing in gear but you cannot give it any gas no matter how slowly you try unless you stab it all at once. This is driving me nuts!! Bulb is firm through all of this and it does not help to pump the bulb.

 

[ZmOz]

Re: Merc 150 wont take fuel (UPDATE)!!!

I assume it's been decarbed?

 

[LubeDude]

Re: Merc 150 wont take fuel (UPDATE)!!!

First thing I did last fall when I got it!<br /><br />What normally causes the coughing, sneezing issue?<br /><br />If it was a car with a carb, I would think it was an accelerator pump, but this has me really stumped.

 

[schaiss]

Re: Merc 150 wont take fuel (UPDATE)!!!

Isn't that engine fitted with an Idle Stabilizer Module? If it has one , it should be located on the top of the Port head. Sounds to me like the unit could be faulty, OR you may luck out (wiring issue). Check the wiring connections on it. The White w/ Black stripe lead and Red w/ White stripe leads should terminate on the outer switch box. The ground lead, if it is loose will cause the type of problem you are having.<br /><br />Best of Luck!

 

[Maximerc]

Re: Merc 150 wont take fuel (UPDATE)!!!

I have my 84 150 apart right now putting in Boysen reeds .. they make a lot of great claims .. supose to help with throttle response. and Idle better with out loading up. Don't know if your reeds might be weak?

 

[LubeDude]

Re: Merc 150 wont take fuel (UPDATE)!!!

I just got back from talking to my Mercury mechanic about this problem, He says that because it is coughing and sneezing that it means that it is lean at Idle, he suggested rejetting the Idle cercuit, says it will solve my problem ??? Worth a try I guess. I am right at sea level.

 

[KCLOST]

Re: Merc 150 wont take fuel (UPDATE)!!!

Lube, <br /><br />I can almost assure you that it is not an electronic issue, as your symptoms do not indicate or justify one... It's got to be fuel related in one way or another....<br /><br />Don't let the mechanic go crasy on the thing before he gets it fixed (ain't that the most helpful advice in the world?)... You never know who you might be dealing with...<br />However, he sounds like he's going in the right direction.....<br />A good cleaning may also be due... Seafoam might help, but that's only a possibility...<br /><br />Let us know.

 

[LubeDude]

Re: Merc 150 wont take fuel (UPDATE)!!!

Thanks KC, He aint gittin any more of my money, I know its nothing very serious, as the engine runs so good otherwise its almost scarey! <br /><br />I assure you, there isnt any crud in this engine anywhere, Its been decarbed and carbs cleaned and, and, and!! Ill do the jet thing and we will see. Only thing is the time to do it. Actually it is just a minor issue right now, as who eases into the throtle anyway? It takes off like a rocket and then you can pull it back if you want, I need to change props first, as I am now running 6,300 RPM at WOT, and that aint good. I do hold it down though, not looking to blow it up!

 

[gss036]

Re: Merc 150 wont take fuel (UPDATE)!!!

Check out this link, it will take you to a troublshooting chart for fuel problems. Maybe it will help you determine what your problem is. Sounds like a gasket problem or maybe reeds. I am not a mechanice by any means, just trying to offer a little help.<br /><br /> http://www.themarinedoctor.com/fuelproblems.htm

 

[LubeDude]

Re: Merc 150 wont take fuel (UPDATE)!!!

Thanks for the link Gary, I wondered where those guys went and didnt know about that forum.

 

[LubeDude]

Re: Merc 150 wont take fuel (UPDATE)!!!

I took the boat out this afternoon when I got home from work to try a different prop, I tried using the choke everytime it wanted to die, and I was able to keep it running at idle without sneezing if I pushed it in ever so often. I also tried to push it in while pushing the throtle forward slowly, and it did pick up without dieing, it wasnt smooth, as it was difficult to do, but it did take off slowly when it wouldnt have otherwise, now we just have to know why it is lean, Im wondering if the boat didnt come from somewhere like Colorado or something and maybe was rejetted for a higher altitude. The prop that was on it when I got it (a High5 23P) had a max RPM of 6,300. The prop I tried this afternoon is a four blade Turbo 14.25 27P, and brought the RPMs down to 5,400. The boat speedometer dosnt work very well, and seems to not go any farther than 57 no matter how much faster you go, I didnt have my freinds GPS with me , but the boat it runnung at least 60+, and what a beautiful roostertail, water preasure was good at WOT. Engine really liked the prop, it sounded really good.<br /><br />So, now what, do I rejet or???

 

[mellowyellow]

Re: Merc 150 wont take fuel (UPDATE)!!!

don't think it's a jet issue, but never know.<br />some guess's:<br />air infiltration somewhere in fuel system?<br />(pressure test system looking for leaks)<br />sticking float?<br />(tap on side of fill bowl sometimes unsticks)<br />when carbs were rebuilt were new floats/needles/<br />seats installed or was it just cleaned?<br />good luck,<br />M.Y.<br />edit/<br />adding this old post by VMAX:<br />I just had the same problem with my 140 horse, 6 cyl mercury. Turned out to be a weak fuel pump. I found out like this:<br />I put the muffs on in the driveway and primed the carbs with the bulb until hard. Then I disconnected the hose to the carbs and installed a 1 foot hose to the pump outlet and ran it to a plastic bottle.<br />I then started the engine and let it run on the fuel in the float bowls at about 1000 rpm (idle speed) until it died (about 20 to 30 seconds). When the engine died, I measured the fuel in the bottle at about 3 ounces, which probably would not be enough to fill the three float bowls up again. I then reasoned that the engine burned fuel faster then the pump could replace it and I disassembled the fuel pump. I checked both check valves and they were OK, but I found that the pump is built with a sandwich of two identical gaskets, with the diaphram in between them. One of the gaskets was installed upside down, which caused a vacuum leak to one of the two chambers in the pump. After reassembling the pump properly with new gaskets and diaphram, I performed the same fill-the-carbs and run-the-fuel-out test, and this time I had about a quart of fuel. Way more than I thought it would take to run the engine at higher speed. The interesting thing about my running problem, was that the motor pumped enough fuel to idle, and if I could coax it into the upper RPM's it would pump OK, but it couldn't pump enough in the 1500 to 3000 range to accelerate normally. I hope this helps you in some way. John

 

[randycc58]

Re: Merc 150 wont take fuel (UPDATE)!!!

lubedude, Have you inspected your reed valves for chipping, warped, or broken?

 

[wilde1j]

Re: Merc 150 wont take fuel (UPDATE)!!!

LubeDude, I think you've answered your own question ... it's lean running at idle that's causing the "sneezing" and don't underestimate the possible result ... burned piston(s), scored cylinder walls, etc. if allowed to persist. If carbs are clean, start looking for cracked or broken hoses connected to crankcase or other sources of air leaks into the crankcase and sources of fuel restriction (trash at pickup screen, etc) and air leaks into fuel lines. Reeds are a very unlikely cause. Good luck!

 

[LubeDude]

Re: Merc 150 wont take fuel (UPDATE)!!!

I did every test I could think of and looked everywhere for an intake leak of somekind, I sprayed carb cleaner all around the base of the intake and carbs and noticed no difference in idle. I actually took the place where I bought the boats word for it that the fuel pump was replaced, but yesterday I took it apart to look at it, It didnt look very good, and there was a new one in a box of stuff that came with the boat so I put it in, It made no difference at all,<br /><br />I ran the boat today with my friends GPS, and the boat runs 65+ MPH at 5,500 with me alone. Yeee, Haaaa!!!

 

[LubeDude]

Re: Merc 150 wont take fuel (UPDATE)!!!

Carbs off on the bench, floats were all over the place, #5 & #6 were close to 1/8th", guess I should have looked at them better, but didnt want to mess them up, guess I couldnt have messed them up much worse than they were. My book says 1/16th ", Is that form the bottom front edge of the float to the front edge of the carb body? I guess this setting is pretty critical. Also is it better to error on the high or low side? Ya, I know, Dont error.<br /><br />All jetts were the right ones for my elevation.<br /><br />Man I hope this solves my problem. as I see nothing else wrong.

 

[mellowyellow]

Re: Merc 150 wont take fuel (UPDATE)!!!

have always set mine to be even with top of bowl<br />when turned upside down. highly reccomend a new<br />needle and seat and maybe even new floats.<br />fingers crossed,<br />M.Y.

 

[LubeDude]

Re: Merc 150 wont take fuel (UPDATE)!!!

Are you saying, "the bottom of the float straight accross with the Carb body"? Man, thats way up there. You are not the only one that has told me this though. They were deffinatly lower than that when I started.

 

[mellowyellow]

Re: Merc 150 wont take fuel (UPDATE)!!!

yep.... might explain not gettin enuff fuel LD?<br />have seen the needles installed upside-down a few<br />times too.

 

[LubeDude]

Re: Merc 150 wont take fuel (UPDATE)!!!

After going through the process of setting the floats, It didnt help at all, I guess I have no choice but to richen the Idle jets. There are no jets in the vents, so thats the only place i can go. My manual says that I have to make them smaller to richen them, so I guess they are air jets.