Hey I have an issue with my engine surging, hope someone can point me in the right direction. I have a Mercury 240 M2 Jet Drive. It starts up fine but when I put more throttle to it, it starts to surge. When I have it in the water it is a back and forth motion. I do have new spark pugs in that maybe has 3 hours on them. I have a TechMate Pro hooked up and can watch my RPM will go fromm 1700 to 1000 and all over the place. When I scan the engine the TechMate shows everything passes. I have a new Throttle position sensor installed and set to .25 with the TPS Test Lead Assembly harness. I also have a new Rev Limiter Assembly. I did take a video of it and will try and post. Any pointers or suggests or any other info you need let me know! thanks
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Mercury 240hp EFI M2 Jet Drive Surging
- Thread starter Dirtyd006
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ok nice, I will take a look at the jet pump and see what I can find out. Thanks!
Back and forth motion??? Not sure I understand that.
While you are down there, look into the steering nozzle. You will need a light. Looking for a rock or plastic bag.
Same thing looking up into the intake tunnel. Look also for impeller leading edge damage.
Do you still have the throttle guardian installed? Find the black with yellow stripe wire. Disconnect it and water test. It is the kill wire. If it has bare spots and grounds out, it can kill the engine.
BTW, have you done a compression test lately?
Have you checked the injector line pressure? Should be 36 psi. Key on, engine off. Have you ever had the injectors serviced? After all, it has been about 20 years.......
Just a few of many things that can go wrong.
While you are down there, look into the steering nozzle. You will need a light. Looking for a rock or plastic bag.
Same thing looking up into the intake tunnel. Look also for impeller leading edge damage.
Do you still have the throttle guardian installed? Find the black with yellow stripe wire. Disconnect it and water test. It is the kill wire. If it has bare spots and grounds out, it can kill the engine.
BTW, have you done a compression test lately?
Have you checked the injector line pressure? Should be 36 psi. Key on, engine off. Have you ever had the injectors serviced? After all, it has been about 20 years.......
Just a few of many things that can go wrong.
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bow of the boat goes up and down and the boat literally goes back and forth in the water. The surging motion related to the RPMs or the motion of full throttle to idle with in seconds.
Thanks for the info. I got under the boat and looked at the grate, the propeller and the nozzle. It looks all in order and doesn't seem to have damage or anything blocking the nozzle or output. I do have the service manual and the parts manual, Im not sure on the throttle guardian. If so, where would that be? There are kinked wires on the rev limiter and the ignition control that I can see. but you make a valid point, a ground wire causing intermediate operation. I will look for that. There has not been a compression test on it. I have not been able to have any boat shop work on it but one. The one that did, didn't know what to do so I have done all the service on it. It wouldn't run at all from the very first. Like the kill switch was bad or something but I found the voltage regulators were bad. I replaced those and it start up perfect. But now I have this problem. I will definitely do a compression test on it. The injectors have not been serviced but I do have 36 psi on the line pressure. Yes it is 20 years old and I know that there hasn't been a lot of hours on the boat for at least 10 years. So I appreciate the info and will look in to it and will follow up. Thaanks
Thanks for the info. I got under the boat and looked at the grate, the propeller and the nozzle. It looks all in order and doesn't seem to have damage or anything blocking the nozzle or output. I do have the service manual and the parts manual, Im not sure on the throttle guardian. If so, where would that be? There are kinked wires on the rev limiter and the ignition control that I can see. but you make a valid point, a ground wire causing intermediate operation. I will look for that. There has not been a compression test on it. I have not been able to have any boat shop work on it but one. The one that did, didn't know what to do so I have done all the service on it. It wouldn't run at all from the very first. Like the kill switch was bad or something but I found the voltage regulators were bad. I replaced those and it start up perfect. But now I have this problem. I will definitely do a compression test on it. The injectors have not been serviced but I do have 36 psi on the line pressure. Yes it is 20 years old and I know that there hasn't been a lot of hours on the boat for at least 10 years. So I appreciate the info and will look in to it and will follow up. Thaanks
IF you have throttle guardian, it should be in driver helm box near the fuse block. Not all boats got it.
Another easy visual inspection-- on top of the engine, just behind the flywheel is the connector for the ignition trigger coil. 6 wire connector. Check the insulation on the wires going to the trigger, under the flywheel.Merc used some crappy insulation on their OEM triggers. This bad insulation crumbles over time (20 years!) causes all kinds of intermittent problems. Good time to check the specs on the trigger wires while you are there.
Compression test- all plugs out, WOT.
Another easy visual inspection-- on top of the engine, just behind the flywheel is the connector for the ignition trigger coil. 6 wire connector. Check the insulation on the wires going to the trigger, under the flywheel.Merc used some crappy insulation on their OEM triggers. This bad insulation crumbles over time (20 years!) causes all kinds of intermittent problems. Good time to check the specs on the trigger wires while you are there.
Compression test- all plugs out, WOT.
I dont believe I have the throttle guardian installed on this boat.
I checked out the trigger assembly. The insulation has really small cracks but nothing major that I can see, but your right it has poor insulation around the wires. I did check the specs on that. The book says 1100-1400 and I have all 3 of them around 1200, so that checked ok. But the book doesn't say anything about the wires to ground. I have 30 ohms to around 8 ohms on all the wires except Red and white. This test is just the wires going to the coils from the plug. I would think that I shouldn't have anything to ground! Any thoughts on that? maybe spots on the insulation that are bad that I cant see? I got a hold of a compression test kit so I will be doing that this week sometime and also going to test the stator.
I checked out the trigger assembly. The insulation has really small cracks but nothing major that I can see, but your right it has poor insulation around the wires. I did check the specs on that. The book says 1100-1400 and I have all 3 of them around 1200, so that checked ok. But the book doesn't say anything about the wires to ground. I have 30 ohms to around 8 ohms on all the wires except Red and white. This test is just the wires going to the coils from the plug. I would think that I shouldn't have anything to ground! Any thoughts on that? maybe spots on the insulation that are bad that I cant see? I got a hold of a compression test kit so I will be doing that this week sometime and also going to test the stator.
It should be. But special dealer only equipment is required. Make the adjustable link the same as old one. You should be close.
I got the trigger assembly in. It was actually a lot easier then i thought, so thanks for the heads up. Followed the book with the #1 piston top dead center, but really can't mess it up too bad. I also did the compression test, that came out good. Each cylinder held and all were about the same pressure. I started it up and ran perfect for the first few minutes. I let it idle the increased RPMs, it sounded fine. Went back to idle and increased rpms and it went back to surging.......The first issue i had with this boat is the it would start and then shut off with in seconds., kinda like the kill switch. After replacing throttle position sensor(dialed in with the harness to mfg specs), temp sensors, two ignition coils and a couple other things. After calling 13 marine shops I finally took it to a shop that actually said they would work on it in Clearfeild Utah, i live in Salt Lake City. It sat there for 2 months till i went and got it because they had no idea what they were doing. Anyhow, i ended up replacing both voltage regulators after checking book specs and the engine started up. I took it to a lake and the surge problem started. So i have put back some of the parts maybe thinking they were the problem. The ones I haven't would be the temperature sensors. It almost seems that the engine warms up and then surges... Have you had any issues with the temperature sensor? or know how they work with the ECM?
Can you find a black wire with yellow stripe in the drivers helm box? That is the kill wire. If it is chafed or broken, that could be causing issues. Find same wire on top of engine. Try disconnecting it and running. Any changes?
Are you able to check fuel pressure while it's running? Starting to sound like fuel starvation from a sticking inlet needle inside the vst.
Check for spark on all 6.
Are you able to check fuel pressure while it's running? Starting to sound like fuel starvation from a sticking inlet needle inside the vst.
Check for spark on all 6.
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I found the black and yellow strip wire in the helm box. The boat shop actually replaced the switch thinking that was the issue. But I checked all the connections in there and looked at the wires. Went back to the motor and disconnected the wire and started it up. It ran perfect! No surging. I increased my rpms and then hooked the kill wire up and it started to surge. Once I disconnected it, went back to running perfect and no surging. That was a great idea so thanks. So I found a direct ground either in the harness or in something else, ohms read .5 and had continuity from ground to the kill wire when the harness is together. I couldn’t really pin point where the ground is. I also had a short to ground on 3 wires in the harness to the motor. 4, 6 and 7. I took all the black tape off and looked at the wires, they all look in good condition. I will have to take a look at the wiring diagram. But I’m pretty sure all the wires shouldn’t go to ground.
I haven’t looked at the gas pressure while running or checked to see if theres a good spark. I’ll definitely check those and maybe I can find the main issue.
I haven’t looked at the gas pressure while running or checked to see if theres a good spark. I’ll definitely check those and maybe I can find the main issue.
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