Mercury Mystery.......

[DavidWebb]

just seems like everytime I take the carbs off and clean them or tinker with them, the boat will run. It's slow out of the hole, like 100+ feet, but it does come up and run. And once it breaks over onto plane, it has all the power it ever had.

Just wandering, if, when I take the carbs off, it is draining fuel back through the filter, like back flushing, that's what's allowing it to get on plane. And when the fuel filter starts to clog again, it's causing it to run lean and that's what's causing the temp sensor to go off. A lean running engine will run hotter than and flooding engine. And it's heating up just enough to set off the alarm. Thus, when I shut it off for 2 minutes, it's cooling off enough for the alarm to cut off.

So, my question is, will a lean running engine smoke and smell like a flooding engine???

I haven't changed the filter yet because, to me, that would cause a fuel restriction. And, to me, that wouldn't cause it to "flood" out.
But, I'm not a mechanic, either, who's seen more engines than I can ever count.

[DavidWebb]

or....everything about this engine says 1998. Except the carbs. The 1998 engine came with a WMV13 carb. Mine are WMV7, which came on the 1996 3.0L. The wmv13 carb has bigger idle air jets than the wmv7. So, if I have the wrong carbs, would that be the cause of my recent balding experience.

[EuropeanAM]

David:

Not sure I follow where you're coming from on the fuel filter. A restricted filter is a restricted filter- a "new" replacement filter should not cause a restriction, until (and unless) it becomes restricted with debris.

I'd need to run your serial number and do some research to comment on the carbs. Very difficult to say what's going on there... how far back do you have history on this engine?

[DavidWebb]

Grasping at straws...had several thoughts bouncing around in my head. If you bounce an idea around in your head long enough, they will make perfect sense after a while. Till you bounce them off someone.

As far as the history, I've had the boat since January. All I know is the serial# comes back to a 1998 3.0L 225 EFI. Somebody evidently blew the EFI somewhere down the line and instead of replacing or fixing the EFI, they replaced it with the WMV7 carbs. So, I guess it really doesn't matter what carb is on it, as long as it's for a 3.0L 225.

[canadabullet]

Is it possible your main jets have worn or are too rich .. You also may have a bad diaphragm in your fuel pump. I would put new main jets , a new fuel pump, and fresh sparkplugs and wires. If your carbs have vent jets in them try running without them to see if things improve.. Running without vent jets will not hurt anything but gas mileage and allows fuel to flow better... The overheating alarm sounds like a waterpump problem.. Install a clear seethrough G3 fuel filter(available everywhere) that has 3/8 nipples so you can see if it is clogging up... .


Modified by canadablazer at 2:21 PM 7/21/2010

[DavidWebb]

I have been running a clear filter since about March. I still have the factory filter installed on the engine.

[canadabullet]

The merc factory filter on the engine is hard to tell if it is clogging.. I would remove it and fit one of those clear 3/8 G3 filters there also... I bet its your fuel pump ....

[DavidWebb]

fuel pump causing it to flood???

[canadabullet]

I have seen bad fuel pumps cause the symptoms you describe...

[DavidWebb]

But, when I did the primer test, it never leaked down, nor did I have any dripping fuel when idling and looking down the venturi.

[DavidWebb]

and, it takes off fine and accelerates fine up to 1800rpm then it just stops and won't go past 1800 no matter how much gas pedal you give it

[redline]

So....this motor sounds suspiciously like an older carb'ed Merc v-6 that's trying to push a boat onto a dry trailer. They would "die" out while loading. SOME of those earlier motors had calibration issues relative to timing, fuel mixture and exhaust relief. The question I would have is that in one of your earlier posts you stated you bought the boat in January, apparently had no issues, then it started to act up, calling for you to take action. Did you CHANGE anything. Fuel, oil, ratio, etc. From what you're describing, it runs as though it's RICH....oil to fuel rich. Very smokey, sluggish, etc. If you are mixing to heavy, it will LEAN out your air / fuel ratio. Another post said you had a lot of "coughing"...precisely what will occur with this with a "rich mixture", again oil / fuel.
I know some of this may seem redundant, and was stated in eralier posts, but....go back to the basics. Something is being missed.
1. Compression test
2. Remote harness
3. Portable fuel tank {known good fuel supply}
4. Timing light {check all cylinders at the problem rpm!}
5. Fuel pressure / delivery. 5-7psi / 3/8 fuel line.
6. Exhaust restriction. Check can to be sure it didn't fracture {mid-section}
7. Bleed system. ALL check valves should be replaced.
8. Good battery, minimum 600CCA.
9. Ventilate the prop more. Heavy pitched wheels LOAD the motor tremendously.
10. Spark plug color? I'll assume they are all "identical"?
11. Replace the diaphram fuel pump {pulse pump}. Cheap.

Suck, squeeze, push and blow.......that's all it's supposed to do....right up to 6100rpm...:)

[canadabullet]

I reread all your posts and , including the other suggestions , would advise you to pull the heads just to make sure you dont have blown headgaskets , which might not be the problem but is easy to find out and eliminate... Also run the motor at night with the cowl off and see if you are getting a lightshow from bad wires or plugcaps... good luck.. I feel confident you will find it. ...If not you might need to split it and see if there are leaking crank seals and do a total rebuild...

[EuropeanAM]

David:

The fuel pump can be checked simply. Remove the pump from the engine (just unbolt it), and remove the outer pulse hose from the pump. Check for fuel or fuel vapors at the two pulse openings (hole on back or pump, nipple on front of pump) while pumping the primer bulb.

My suggestion would be to have an 857005A1 pulse pump kit on hand, and simply install it while you're there. Probably needs it, based on it's age- regardless of testing results.

I still suspect your problem is an exhaust restriction. Go back to what we talked about.... if the engine can't breathe properly, it WILL run rich.

[DavidWebb]

The oil tank has been removed, so I mix my own gas and oil. 50:1. And I use a measuring cup to do so. I didn't change anything till after I got it back from the mechanic who cleaned the carbs. Once I got it back from him, it would not get over 1800. I took it back to him, and he said it was the crank sensor. He replaced the crank sensor. I did check the air gap and it is right. I replaced the TPS, afterwards, I found out that I was reading the voltage wrong, so it wasn't defective to begin with, the mechanic had put it on 180deg out of whack. I changed the needle and seats last week. That's all that has been changed. as for:
1. compression- 107-110# per cylinder, cold engine.
2. Remote harness- I have checked every wire that I can get my hands on, and no broken wires and all are hooked where they should be according to the Merc Manual.
3.Portable Tank- I did run it on a remote tank with fresh gas and oil, no change.
4. Timing light- I have hooked a timing light to all cylinders, I have not done this at 1800rpm, but I have marked the flywheel where each cylinder should fire and each one did fire in time.
5. Fuel pressure- I don't have a pressure guage to test the fuel pressure.
6. Exhaust- I did inspect the exhaust, I did not see any cracks. The "honeycomb" at the top was clogged and I was able to clean 8 of the ports out. No change.
7. Bleed system- I haven't messed with the bleed system.
8. Battery- It does have a good battery. 660CCA if I remember correctly.
9. Prop- I haven't pulled the vent plugs on it yet. We will be going out again Friday night. I will pull the plugs then.
10. Spark plugs- oily, wet look like the engine is flooding. I put new plugs in it last Saturday.
11. Fuel pump- I haven't changed the fuel pump. I didn't see it causing a flooding situation. But I can change it fairly quickly.

[DavidWebb]

Will need the gaskets and seals to put it back when I get done.

[redline]

1. compression- 107-110# per cylinder, cold engine. Ok, good enough for now.
2. Remote harness- I have checked every wire that I can get my hands on, and no broken wires and all are hooked where they should be according to the Merc Manual. I'd still like to see you run it with a remote harness. This eliminates the boat, takes it out of the equation. You'd be surprised at the amount of key switches, tachs, and BOAT WIRING that cause engine maladies.
3.Portable Tank- I did run it on a remote tank with fresh gas and oil, no change. Good.
4. Timing light- I have hooked a timing light to all cylinders, I have not done this at 1800rpm, but I have marked the flywheel where each cylinder should fire and each one did fire in time. You need to do this in the problem zone. You'd be surprised again at how this can sometimes "change".
5. Fuel pressure- I don't have a pressure guage to test the fuel pressure. Need to aquire one, be sure the pressure does not exceed 10psi.
6. Exhaust- I did inspect the exhaust, I did not see any cracks. The "honeycomb" at the top was clogged and I was able to clean 8 of the ports out. No change. Pull gearcase and view from bottom UP. Should be clear.
7. Bleed system- I haven't messed with the bleed system. CHANGE all check valves. If the bleed system is not functioning propely the motor will run RICH. 8. Battery- It does have a good battery. 660CCA if I remember correctly. Good. Do a load test, be sure that it MAINTAINS a charge. Just because it reads 12v does not mean it's good. Put a gauge on it when at about 3000 rpm....you should see about 13.7 volts..+/-.
9. Prop- I haven't pulled the vent plugs on it yet. We will be going out again Friday night. I will pull the plugs then. Let us know how this works, but remember this would be a band-aid. The recommendation is to see if it IMPROVES with ventilation.
10. Spark plugs- oily, wet look like the engine is flooding. I put new plugs in it last Saturday. Sounds normal. They are most always "wet".
11. Fuel pump- I haven't changed the fuel pump. I didn't see it causing a flooding situation. But I can change it fairly quickly. DO IT.

[EuropeanAM]

<table width="90%" cellspacing=0 cellpadding=0 align=center><tr><td>Quote, originally posted by redline &raquo;</td></tr><tr><td class="quote">1. compression- 107-110# per cylinder, cold engine. Ok, good enough for now.
2. Remote harness- I have checked every wire that I can get my hands on, and no broken wires and all are hooked where they should be according to the Merc Manual. I'd still like to see you run it with a remote harness. This eliminates the boat, takes it out of the equation. You'd be surprised at the amount of key switches, tachs, and BOAT WIRING that cause engine maladies.
3.Portable Tank- I did run it on a remote tank with fresh gas and oil, no change. Good.
4. Timing light- I have hooked a timing light to all cylinders, I have not done this at 1800rpm, but I have marked the flywheel where each cylinder should fire and each one did fire in time. You need to do this in the problem zone. You'd be surprised again at how this can sometimes "change".
5. Fuel pressure- I don't have a pressure guage to test the fuel pressure. Need to aquire one, be sure the pressure does not exceed 10psi.
6. Exhaust- I did inspect the exhaust, I did not see any cracks. The "honeycomb" at the top was clogged and I was able to clean 8 of the ports out. No change. Pull gearcase and view from bottom UP. Should be clear.
7. Bleed system- I haven't messed with the bleed system. CHANGE all check valves. If the bleed system is not functioning propely the motor will run RICH. 8. Battery- It does have a good battery. 660CCA if I remember correctly. Good. Do a load test, be sure that it MAINTAINS a charge. Just because it reads 12v does not mean it's good. Put a gauge on it when at about 3000 rpm....you should see about 13.7 volts..+/-.
9. Prop- I haven't pulled the vent plugs on it yet. We will be going out again Friday night. I will pull the plugs then. Let us know how this works, but remember this would be a band-aid. The recommendation is to see if it IMPROVES with ventilation.
10. Spark plugs- oily, wet look like the engine is flooding. I put new plugs in it last Saturday. Sounds normal. They are most always "wet".
11. Fuel pump- I haven't changed the fuel pump. I didn't see it causing a flooding situation. But I can change it fairly quickly. DO IT.
</td></tr></table>

+1

I still think you need to go further on #6. We can discuss this further by phone sometime if you would like.

BTW.... do you have STEEL REEDS or CARBON FIBER REEDS in this engine? Have they been removed and inspected?

[DavidWebb]

I haven't actually taken them out. I used a flexible pen light and a dentist mirror to inspect them. They looked to me like they were carbon fiber. They were a dark gray color. And when I get ready to go further, I may need you to get me the gaskets to put it back together.

[canadabullet]

One more small detail... Check that the gaskets between the airbox and carbs are not upside down...