2008 Mercury Optimax 115 just died

[OldDude]

Last night my wife and I were fishing. We were in a no wake zone at an idle and the motor just died. It wouldn't immediately restart. We fished some then the motor started, sputtered and died again. Sounded like a fuel issue. I checked the fuel bulb and it wasn't firm like it has always been in the past. We trolled to the ramp, but thank God it started and loaded with no problems. Now I'm worried and hesitant to take it to anywhere bigger than our local lake.

Any ideas? Because it started and loaded Im thinking its got junk in the fuel. Maybe a new filter.

Its a 2008 Nitro 189 Sport with the Mercury Optimax 115. We just bought it in December 2020. We have had it on the lake at least 6 times a month since we bought it and it always runs great.

 

[OldDude]

An update... As a precaution I replaced the fuel line, primer bulb, re-built the diaphragm on the VST, replaced the fuel filter, and drained the VST (no water present). Started it up and had the same issue. I replaced the fuel pick up lone and the anti-syphon valve. Same issue.

As it starts right up when primed, and runs well until it runs out of fuel from the bulb tot he VST, Im thinking maybe a venting issue. Seems like negative pressure is keeping it from being able to pull fuel from the tank.

I assume the item in the pic is the vent? Is it anything special or just a 90 degree fitting? Any ideas?

 

[cceguy]

To help narrow down the problem, put a clear piece of tubing (or clear fuel filter) in the fuel line after the primer bulb, and check for bubbles or no flow. Open the gas tank fill cap - that should eliminate a vent problem. Check spark plugs, compression, and ignition system. I think your motor has DFI, but for others, if the motor has carburetors, check for defective choke operation.

 

[OldDude]

Dfi. Plugs replaced the same time as the first fuel line fix. Boat is running amazing when I can keep fuel to it. I opened the gas cap. Same problem. Is there some type of valve in the 90 degree fitting the vent hose in the top of the tank?

 

[HAIRLESSxWOOKIE]

Sounds like its time to replace your fuel pump.

 

[cceguy]

I don't think there is a valve in the vent hose fitting. My 1st guess is a bad fuel pump or restriction in a fuel line. If you have a vacuum gauge, prime the engine with the primer bulb, pull the line from the tank to the primer bulb, and attach the gauge to the line. Start the engine - the gauge should read about 4 psi. Another option is to pull the line from the tank and insert the hose into a separate container of gas. Start the engine and see if gas is being pulled through the line. While running, pull the line out and put a finger over the end of the hose - you should feel a vacuum.
If not pulling gas, it might be a failing fuel pump or a restriction in a hose. I had a problem with the the 9 hp motor on my flat bottom boat getting it started. Once started it ran fine.
But if it sat for more than an hour it was hard to start. I replaced the bulb twice - no change. then I found out if I held the bulb above the engine, and pulled the rope a couple of times, it started right up. Then I bought a complete hose assembly, and all was good. I then installed a fuel filter just before the engine. I noticed I had installed the filter with the arrows going the wrong way, so reinstalled it the right way. Then it would not start again, until I held the bulb above the engine. Turns out the line I was using has a liner on the inside that after I pulled the filter would bunch up and restrict the line when I reinstalled the filter. Pulled the filter, cut an inch off the line, and all was good. So I looked at the lines I replaced, and found the same thing. Not sure, but I think when I used the primer bulb the pressure on the bunched up liner was great enough to seal off the line, but once started the fuel pump did not have enough pressure to close the line, and the fuel would get thru.
Good luck.

 

[jerry shack]

Did you have some one squeeze the primer bulb while the motor is running to see if it would stay running that way? That motor has 3 fuel pumps. 2 of which are in the vst tank and a mechanical lift pump that can be rebuilt. That pulls fuel from the fuel tank to the vst tank. I guising the diaphragm that you rebuilt on the vst tank is the fuel lift pump I talking about. However CCEGUY has some good ideas to try.

 

[OldDude]

Its not immediately starving for fuel. I posted some videos last night.









Its running for 20-25 minutes before the issues start. Its done this 4 separate times now. Ive done new fuel line from the tank to the bulb, new bulb, new fuel line from the bulb to the pulse pump, rebuilt the pulse pump, replaced the fuel tank pick up and anti syphon, checked the vent...

This one has two fuel pumps, both inside the VST. Neither are cheap. I cant afford to start throwing parts at it at $400 a part. How would I know which was bad or going bad?

Any why does it wait 20-25 minutes to start acting up?

 

[jerry shack]

Olddude,
this is what I think might be happing even though it's pretty remote but have seen it before. There might be something floating around in your fuel tank and when it gets near the out let pipe it shuts off the gas. Then when the fuel pump pressure is off it floats away. Easy test is to start by a prosses of elimination which you are doing, so get a remote fuel tank or big coffee can stick the hose in it and run it see what happens.

 

[cceguy]

Its not immediately starving for fuel. I posted some videos last night.









Its running for 20-25 minutes before the issues start. Its done this 4 separate times now. Ive done new fuel line from the tank to the bulb, new bulb, new fuel line from the bulb to the pulse pump, rebuilt the pulse pump, replaced the fuel tank pick up and anti syphon, checked the vent...

This one has two fuel pumps, both inside the VST. Neither are cheap. I cant afford to start throwing parts at it at $400 a part. How would I know which was bad or going bad?

Any why does it wait 20-25 minutes to start acting up?

Try removing the fuel cap when it starts to act up - that should eliminate a fuel tank vent problem. Have you tried the clear tube in the line? Really think it is a vent problem. Might be an ignition problem that heat from the engine causes. But I would think it would show up in 5 to 10 minutes, not 20 minutes. Maybe a sensor that detects a problem that can shut down the motor before damage occurs, or a sensor that malfunctions when it heats up. Just my thoughts - I'm no expert, just know enough to be dangerous.

 

[OldDude]

I have cleared the vent line. I checked the vent fitting as well as the one in the gas filler cap.

Someone in a different forum said the fuel system holds enough fuel to run the engine for 20 to 25 min at 1500 rpm amd that's why it's dying... it's running out of gas in the fuel system from the primer to the VST.

The only issue is if that were the case, it would run another 20 to 25 min after it's pumped back up. It only run less than 10 min after it has died once.

 

[cceguy]

I have cleared the vent line. I checked the vent fitting as well as the one in the gas filler cap.

Someone in a different forum said the fuel system holds enough fuel to run the engine for 20 to 25 min at 1500 rpm amd that's why it's dying... it's running out of gas in the fuel system from the primer to the VST.

The only issue is if that were the case, it would run another 20 to 25 min after it's pumped back up. It only run less than 10 min after it has died once.

Jerry had a great idea about using a remote fuel tank or can of gas - eliminating the fuel tank as a problem. And his thoughts about something floating could possibly happen in the primer bulb or any where in the line. Remote yes, but possible. Also, the fact that it runs for 20 minutes the 1st time, and 10 minutes the second time could mean it is heat related. After it dies the 1st time, the engine (or another component) cools just enough to start again, but reaches the shutoff temperature quicker. Just something to ponder.

 

[NEBRVET]

I didn't read the entire thread, so I apologize if this is a repeat. Ethanol fuel will eat away at your fuel line causing it to deteriorate. I would replace the entire fuel line, primer bulb and filter. Drop the bowl from the carbs and make sure they are void of debris.

 

[Kirby Wilson]

Check your squeeze bulb to see if it is collapsed when the motor starts to act up. If the squeeze bulb collapses then the problem is at the bulb back including the tank. If not then it is in the motor. I have had dirt daubers build nest in some boat's gas vent before.

 

[Notrab77]

Probably a long shot, but I had issues on my 2008 150 EFI yesterday similar to this where the engine would keep dying on m. The motor acted like it was starving for gas and we could actually keep it running as long as we pumped the bulb. Once I removed the cover and inspected, I discovered that the wire on the bottom of the fuel filter had come off. Once I plugged it back in, it ran great again. No idea if the Optimax has the same fuel filter / wire or not, but thought I would throw it out there.

 

[OldDude]

Thank you all. Still working on it.

 

[Tommyboy1959]

Last night my wife and I were fishing. We were in a no wake zone at an idle and the motor just died. It wouldn't immediately restart. We fished some then the motor started, sputtered and died again. Sounded like a fuel issue. I checked the fuel bulb and it wasn't firm like it has always been in the past. We trolled to the ramp, but thank God it started and loaded with no problems. Now I'm worried and hesitant to take it to anywhere bigger than our local lake.

Any ideas? Because it started and loaded Im thinking its got junk in the fuel. Maybe a new filter.

Its a 2008 Nitro 189 Sport with the Mercury Optimax 115. We just bought it in December 2020. We have had it on the lake at least 6 times a month since we bought it and it always runs great.

Same thing happened to my 07. VST seals bad, maybe sucking air. Cheap part but a little Labor.

 

[BrianM$teven$]

Thank you all. Still working on it.

Any updates? Came across your thread because my 150 ProXS may be having same issues so would like to mail or text you to compare symptoms and or what you have found. Thanks.

 

[Tommyboy1959]

An update... As a precaution I replaced the fuel line, primer bulb, re-built the diaphragm on the VST, replaced the fuel filter, and drained the VST (no water present). Started it up and had the same issue. I replaced the fuel pick up lone and the anti-syphon valve. Same issue.

As it starts right up when primed, and runs well until it runs out of fuel from the bulb tot he VST, Im thinking maybe a venting issue. Seems like negative pressure is keeping it from being able to pull fuel from the tank.

I assume the item in the pic is the vent? Is it anything special or just a 90 degree fitting? Any ideas?View attachment 1450View attachment 1451View attachment 1452View attachment 1453

 

[Tommyboy1959]

An update... As a precaution I replaced the fuel line, primer bulb, re-built the diaphragm on the VST, replaced the fuel filter, and drained the VST (no water present). Started it up and had the same issue. I replaced the fuel pick up lone and the anti-syphon valve. Same issue.

As it starts right up when primed, and runs well until it runs out of fuel from the bulb tot he VST, Im thinking maybe a venting issue. Seems like negative pressure is keeping it from being able to pull fuel from the tank.

I assume the item in the pic is the vent? Is it anything special or just a 90 degree fitting? Any ideas?View attachment 1450View attachment 1451View attachment 1452View attachment 1453

if it runs while you pump full ball its the foil pump