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Mercury 115 4 Stroke- Bogging Down?

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41 - 60 of 133 Posts
Discussion starter · #41 ·
Just got into it at home for the evening. There are two fuel pumps within the fuel system module. The low-pressure turns on when you turn the key and I can hear that one running. The float within that system tells the pumps went to kick in. The low-pressure kicks in when it doesn’t need much in the high-pressure kicks in when it needs a lot. So narrowing it down it looks like either the float is not doing its job or the high-pressure fuel pump is not kicking in.


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Discussion starter · #42 ·
I’m not feeling like I’m home free yet but……
With the old gas out of her she started up perfect, idled perfect and accelerated all the way to 4500 rpm’s perfect. I have a hard time believing this entire thing was bad gas but I’m hoping it’s true! I won’t have a chance to get her in the water until Thursday evening but I’m keeping my fingers crossed.


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#44 ·
FreeTime said:
I’m not feeling like I’m home free yet but……
With the old gas out of her she started up perfect, idled perfect and accelerated all the way to 4500 rpm’s perfect. I have a hard time believing this entire thing was bad gas but I’m hoping it’s true! I won’t have a chance to get her in the water until Thursday evening but I’m keeping my fingers crossed.


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Click to expand...
Well, welcome to my issue last year. I bought the boat from a guy and unknown to me he never put stabil in it and had regular no lead sitting all winter. I tired everything and then thought of the water in gas. I changed the water separator and added dry gas/ stabil. It would only get up to 7 mph maxed out and then after I figured out the water issue I was going 38 mph
 
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#45 ·
Even with stabilizer, the shelf life of gasoline is only about 4-6 weeks. After that in s vented fuel system, the lighter constituents evaporate away and the fuel will make less power and can be harder to ignight at proper timing.
 
Discussion starter · #47 ·
Well I just came back from a test and I’m right back to where I started. Started up an idol perfectly at the dock, went and parked the truck, backed away from the dock and within 100 yards it died. Won’t restart.

Just got home I’m going to hook up the muffs. I have no idea how it’s getting enough gas to start and run while at the dock but after cranking for a while the first fuel filter is empty.

The only thing I can think right now is that there is some sort of a vent leak. When you turn the key I can hear a fuel pump kick in but nothing is sucking up. Aaaaahhhggg!!!! This thing is going to be the death of me!




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#48 ·
FreeTime said:
Well I just came back from a test and I’m right back to where I started. Started up an idol perfectly at the dock, went and parked the truck, backed away from the dock and within 100 yards it died. Won’t restart.

Just got home I’m going to hook up the muffs. I have no idea how it’s getting enough gas to start and run while at the dock but after cranking for a while the first fuel filter is empty.

The only thing I can think right now is that there is some sort of a vent leak. When you turn the key I can hear a fuel pump kick in but nothing is sucking up. Aaaaahhhggg!!!! This thing is going to be the death of me!




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Click to expand...
This is where testing with a small portable tank and new hose will let you know if there is an air leak or something else wrong in your built in fuel system.
 
Discussion starter · #49 ·
I have a new theory. Alternator. When it ran fine at home the other day it had the charger on the battery. At the dock, it runs fine and then quits. Maybe because it’s not charging and being an EFI it needs power. It runs out the battery and then dies. At home with charger on it was getting power to replenish the lost and on the water nothing is replenishing the power it’s sucking up. I have the charge on it right now, if it will run when it gets replenished I think I have a route to go on.


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Discussion starter · #50 ·
Getting somewhere positive today.
So before I went down my theory of testing the alternator I decided to go back through everything again. After trying to start a couple of times and hearing the fuel pump kick in I disconnected the first fuel filter just inside the motor. It had no gas. This tells me the fuel pump wasn’t sucking it up or there was a clog. Disconnected the fuel line between the motor and the deck where it leads to the main fuel tank. When I tried to blow through the line I couldn’t. Nothing getting through. Replaced the fuel line and bingo! Fuel pumped sucked up gas and she fired, ran good. No clue how I missed this before.

Back to the launch, started and ran well but not superb. Was able to run all the way to full throttle and did for around 30 minutes up and down the river.
BUT..... I’m not getting the acceleration or top end I’m used to. RPM are a good 800 ish short of what it will normally do and overall speed was 5-7 mph short of normal.

Back home and pulled the plugs. All have a decent amount of carbon build up, 3 tips are white and one totally black.

I’m getting somewhere but not home free yet! I keep looking.
To be continued.....
Image



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#51 ·
Sounds like your getting closer. If you can find it use gas that is alcohol free. The regular gas we use in our vehicles has so much methonol in it that I creates alot of water and dissolves rubber lines and such in your fuel system. Unless you drained your tank totally dry I'm betting you still have water in the bottom if your gas tank. I'm not saying that's your problem but the gas now days causes a lot of problems in small engines. I add sea foam in every can of gas I use also
 
#52 ·
FreeTime said:
Getting somewhere positive today.
So before I went down my theory of testing the alternator I decided to go back through everything again. After trying to start a couple of times and hearing the fuel pump kick in I disconnected the first fuel filter just inside the motor. It had no gas. This tells me the fuel pump wasn’t sucking it up or there was a clog. Disconnected the fuel line between the motor and the deck where it leads to the main fuel tank. When I tried to blow through the line I couldn’t. Nothing getting through. Replaced the fuel line and bingo! Fuel pumped sucked up gas and she fired, ran good. No clue how I missed this before.

Back to the launch, started and ran well but not superb. Was able to run all the way to full throttle and did for around 30 minutes up and down the river.
BUT..... I’m not getting the acceleration or top end I’m used to. RPM are a good 800 ish short of what it will normally do and overall speed was 5-7 mph short of normal.

Back home and pulled the plugs. All have a decent amount of carbon build up, 3 tips are white and one totally black.

I’m getting somewhere but not home free yet! I keep looking.
To be continued.....
Image



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Click to expand...
Hey free I just came across your post, I have same motor 115 merc 4stroke but a 2004. I had a similar issue myself, main problem ended up being the regular gas previous owner user destroyed the old gas line and bulb. I replaced both, cleared fuel lines and replaced filter and plugs. Seems to run great but I’m not getting the top end speed I was before and like you I’m about 800 rpms short of where I should go topper out and about 5mph slower then it should be. My next step might be to have injectors cleaned as that’s only other option I can think of. I’ll be watching your thread and good luck pls keep your progess posted. If I can fingers mine out I’ll post for you
 
Discussion starter · #53 ·
gatorman841 said:
My next step might be to have injectors cleaned as that’s only other option I can think of. I’ll be watching your thread and good luck pls keep your progess posted. If I can fingers mine out I’ll post for you
Click to expand...
Lets keep each other informed and maybe 2 heads are better than one! First one to figure it out gets a few cold beers on the other!
 
Discussion starter · #55 ·
gatorman841 said:
Curious before this issue what kinda top speed were you getting from your motor?
Click to expand...
Mine is on a 1750 Lund Tyee, so its a heavy boat. With a full load, full 25+ gallons of gas, and 2-3 guys I would get 36-38ish.
Top end on Saturday was 30.5 with just me, no gear, and only about 5 gallons of gas in the tank.
 
Discussion starter · #57 ·
bowhunter426 said:
Freetime. Was the hose Grey with orange lettering? If it was is the fuel filter still clean?
Click to expand...
It was gray hose but with black lettering. The fuel and it looked fine by color. But the interior liner of the hose had come apart. In this picture you can see the interior liner hanging loose from the rest of the hose
Image



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#58 ·
FreeTime said:
Mine is on a 1750 Lund Tyee, so its a heavy boat. With a full load, full 25+ gallons of gas, and 2-3 guys I would get 36-38ish.
Top end on Saturday was 30.5 with just me, no gear, and only about 5 gallons of gas in the tank.
Click to expand...
Well sounds like we are getting roughly the same speed right now.... I’m barely hitting 30 solo with light gear and full tank.
 
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