2001 Mercury 115HP EFI 4 strock losing power after 40 minutes

[Zippady]

TLR - If an engine is having a fuel feeding issue how long after re-priming the line would you expect the roughing running to clear?


Full Story
The last 2 times I've used the boat I've lost power after running for around 40 minutes, twice each run (4 times in total, that is about how long I was running for so didn't run for another 40 minutes for it to happen again). Each day it happened once at around 3/4 throttle and the other time when doing about 6kts.

Both myself and the friend I had with me think it sounded like the engine was starved of fuel.

The first time it happened i turned off the engine to have a look around and noticed that the priming bulb on the fuel line felt very empty, I pumped it back up and re-started the engine, it fire back up and was fine. On the way home it did it again but happened as I was pulling up to the boat ramp, with the engine still running I pumped the bulb but there was no improvement to the rough running, since i was now at the ramp I turned it off and packed up the boat.

When i got home I inspected the fuel lines and found one from the underfloor tank that was a little kinked so i replaced the line while also adding a two way selector before the filter and a connection for a portable tank (to feed through the filter).

Today was the second day, we were doing about 6kts and it started running rough, once again the bulb felt empty (I don't actually no what it should feel like, I don't expect it to be hard but i couldn't feel fuel during the first few pumps) so i gave it a few pumps but it didn't fix the issue, I changed to fuel tap over to the portable tank I was carrying with fresh fuel and gave the primer on the tank connector a few squeezes but no change. I turned the motor off gave it a minutes and turned it back on and it fired up and run fine for another 40 mins. The second time it occurred I turned the motor off and without doing anything else tried to restart it, it restarted but sounded very sick still, I checked the bulb on the portable tank I'd been running off for the lat 40 minutes and it felt fine, I check the main bulb and it once again felt empty so I gave it a pump, the running smoothed out a little, I gave it some throttle and the motors accelerated smoothly and run fine all the way home.

My plan from here is to replace the rest of the fuel line I didn't do when I did the line from the internal tank, that is only 4ft of line from the water separating filter to the engine, I'll also replace the filter (it is the clear bowl type and there is no water in the bowl) and the priming bulb.

Does the sound like a reasonable plan?
is there anything else worth checking?

I'm concerned that the problem doesn't immediately go away when I re-prim the fuel line and it was a couple of minutes of running off the portable tank the first time today after re-priming with no improvement before I turned it off. The problem also hasn't actually been resolved without restarting the engine, along with it happening intermittently so doesn't seam like a persistent fuel feed problem but rather something is happening, in the back of my mind I'm worried that it could be something with the engine either causing it or not clearing when it happens without the restart.

Due to the nature of the problem it takes a wile to trouble shoot and I'm going to have to take the boat out and keep close to home to give it a run and see if it has been resolved so the more I can do at home before going out again the better.

 

[Texasmark]

Empty squeeze bulb when it should have been soft (moderately full of fuel) sounds like several problems:

Fuel filters dirty/clogged....fuel pump is sucking fuel but the outlet is full so there IS NO fuel flow to keep the bulb full even though the pump is trying to suck. Merc mid range have filters in the engine, under the cowl......to name one and they do get clogged with little, hard, tan, pieces of crud nowadays....just replaced mine and it was full giving me your same problem.

Next would be inlet to bulb clotted with the same thing, or a blob of fuel-water gel which has happened to me when you had water in your tank and added a water remover after market chemical to the fuel tank.

Fuel tank inlet filter clogged with the same crud.....fuel line cracked allowing fuel pump to suck air not fuel (included bad check valves in squeeze bulb or bulb itself.......fuel tank vent clogged such that removing fuel causes a vacuum in the tank greater than the fuel pump's ability to suck fuel against it.

Fuel pump malfunction, check valves or diaphragm rupture.

That'll give you a few places to look.

 

[QBhoy]

As mentioned, fuel filter would be a start.
next I’d be checking the vent is open or clear on tank, remote or otherwise.
next I’d be checking if the engine is charging the battery and it’s not the case that you are running out of power to keep the engine running.

 

[Zippady]

Thanks for the feedback, I’ll grab a replacement for that engine mounted fuel filter. The batteries are getting a good charge and I was leaning away from a tank vent issue since it did the same with the portable tank and the vent was definitely open on it.

from what has been said about the bulbs, because the bulb on the portable tank before the off motor filter had fuel in it but the bulb after the filter was empty I’m guessing the problem could also be at that filter? That filter isn’t very old, is there anything special I might have missed when installing it? I didn’t fill it with fuel before hand or anything, I just wet the O ring and screwed it on

 

[Texasmark]

I have a manual on that engine which I accidentally purchased when looking for my 2002 carbureted 115 manual. When I go out to the shop in a couple of hours I'll have a look in it and see if it has special instructions for filter replacement.

 

[flyingscott]

After the motor starts the bulb should be soft, That is normal. I would look for loose wires and run a timing light on the plug wires when that happens.

 

[bignev213]

TLR - If an engine is having a fuel feeding issue how long after re-priming the line would you expect the roughing running to clear?


Full Story
The last 2 times I've used the boat I've lost power after running for around 40 minutes, twice each run (4 times in total, that is about how long I was running for so didn't run for another 40 minutes for it to happen again). Each day it happened once at around 3/4 throttle and the other time when doing about 6kts.

Both myself and the friend I had with me think it sounded like the engine was starved of fuel.

The first time it happened i turned off the engine to have a look around and noticed that the priming bulb on the fuel line felt very empty, I pumped it back up and re-started the engine, it fire back up and was fine. On the way home it did it again but happened as I was pulling up to the boat ramp, with the engine still running I pumped the bulb but there was no improvement to the rough running, since i was now at the ramp I turned it off and packed up the boat.

When i got home I inspected the fuel lines and found one from the underfloor tank that was a little kinked so i replaced the line while also adding a two way selector before the filter and a connection for a portable tank (to feed through the filter).

Today was the second day, we were doing about 6kts and it started running rough, once again the bulb felt empty (I don't actually no what it should feel like, I don't expect it to be hard but i couldn't feel fuel during the first few pumps) so i gave it a few pumps but it didn't fix the issue, I changed to fuel tap over to the portable tank I was carrying with fresh fuel and gave the primer on the tank connector a few squeezes but no change. I turned the motor off gave it a minutes and turned it back on and it fired up and run fine for another 40 mins. The second time it occurred I turned the motor off and without doing anything else tried to restart it, it restarted but sounded very sick still, I checked the bulb on the portable tank I'd been running off for the lat 40 minutes and it felt fine, I check the main bulb and it once again felt empty so I gave it a pump, the running smoothed out a little, I gave it some throttle and the motors accelerated smoothly and run fine all the way home.

My plan from here is to replace the rest of the fuel line I didn't do when I did the line from the internal tank, that is only 4ft of line from the water separating filter to the engine, I'll also replace the filter (it is the clear bowl type and there is no water in the bowl) and the priming bulb.

Does the sound like a reasonable plan?
is there anything else worth checking?

I'm concerned that the problem doesn't immediately go away when I re-prim the fuel line and it was a couple of minutes of running off the portable tank the first time today after re-priming with no improvement before I turned it off. The problem also hasn't actually been resolved without restarting the engine, along with it happening intermittently so doesn't seam like a persistent fuel feed problem but rather something is happening, in the back of my mind I'm worried that it could be something with the engine either causing it or not clearing when it happens without the restart.

Due to the nature of the problem it takes a wile to trouble shoot and I'm going to have to take the boat out and keep close to home to give it a run and see if it has been resolved so the more I can do at home before going out again the better.

We have a volvo Penta petrol engine 3 L 4 cylinder. it's states on the rocker cover to set the timing ignition at 2 degrees after top dead centre but the engine doesn't like to run at this setting as soon as we advance it to about 7 degrees before top dead centre the engine smooth out the engine likes to run at that setting. would you say this is the correct setting or should i leave it at or am I missing out on something ?

 

[Zippady]

I haven’t disappeared, just got called away it’s work unexpectedly. I’m home now and have all the parts except the engine mounted filter (it is on its way), I’ll change all of that then if It still has issues I’ll get a timing light. Either way I’ll let everyone know.