No power from 2,000-4,000 rpm on 240 efi

[challenger01]

Hello,

My 2001 240 efi is not running correctly.

I am premix premium gas with 50:1 penzoil synthetic ratio for the past several seasons with no issues.

I start up ok and when I get to about 2k rpm the boat bogs and feels like it will stall almost like it’s not getting fuel. The only way to keep it going is to push the throttle and get to higher rpms. It then jumps and takes off like normal.

When I push it to 4,000+ it runs normal. I am wot at about 6000+ rpm.

The boat seems to lose all power when I drop the throttle to 3,500-4,000 or lower.

I don’t have issues starting hot or cold.

I replaced the plugs and they all looked uniformly oily but not burnt.

I changed the water separator filter and I checked the steel in line filter and I was able to push air through. I will change that ASAP.

I have an extra port side temperature sensor at home so that will be the next change along with the fuel filter.

I have not opened up the vst, but could this filter be an issue? Are these symptoms of the dreaded throttle position sensor?

Just looking for advise to see if this sounds like a fuel or electrical / sensor issue.

By the way I run a 2 battery setup and always keep one available for startup and don’t mess with the radio when this battery is on. I don’t think it would be low battery voltage but not sure.

Thanks

 

[Tim75]

At about 2800 rpm, the engine is trying to switch from low speed to high speed. Not sure about how or why.
I had the same issue on my 2000 year 240 efi. I checked the resistance of each coil from the trigger base. They were each nominal. The symptoms still pointed to the trigger.
If you still have the ORIGINAL trigger, they also had issues with poor quality insulation on the wires. I bought a new CDI brand (cdielectronics.com) unit (ebay) for half of Merc price. Replaced and engine revs from 1200 to 6300 smoothly.

Still running oil injection. Single battery.

 

[challenger01]

My summer has been extremely busy so I took my boat to a shop and they diagnosed a bad high pressure fuel pump in the vst. The very expensive pump was replaced and I just picked it up tonight with no change to the original symptoms.

I have no problem at idle but it struggles to get past 2000 rpm. If I push the throttle hard it takes off and races to wot around 6000+. The boat will run 50+ mph.

I can cruise around 4500 rpm, but when it drops lower it completely drops off and almost stalls.

I have attached a link to a YouTube video of the boat. If this is what your boat was doing I would appreciate hearing if the trigger was the fix.

Thanks

https://youtu.be/b_Gp54EzViU

 

[Tim75]

If your engine would run at 6000 rpm, I would have been very doubtful that your vst pump was an issue.

Almost exactly what my boat (same year & engine) was doing. Previous msg.

A little good news-- If your engine is hitting 6000 rpm, I think we can rule out mechanical issues.

 

[challenger01]

Thank you for reviewing my video. I will have to further explore that potential issue as you initially indicated.

I have a copy of the manual so I will look at what is involved in checking the trigger. Any advice is welcome.

It’s good to hear that someone else had a similar issue and found the solution. If you have any further information about the off brand trigger I would appreciate it.

Thanks,
Brian

 

[Tim75]

Puller- ebay 123709203393
Trigger--ebay 122664869145

Checking the trigger takes about 5 minutes. Need an ohm meter.

I have about 10 hours so far on my cdi trigger. Direct bolt-in replacement. It took about 45 minutes start to finish to replace.

 

[challenger01]

I just wanted to follow up that the issue ended up being a bad throttle position sensor. Of course this is the nearly $500 sensor but the multimeter indicated jumping resistance at a point above idle and ok at wot.

With a new fuel pump and tps the boat feels better than I can remember. Easy start, smooth acceleration and 6000+ wot.

Hope this helps someone else

 

[Tim75]

I just wanted to follow up that the issue ended up being a bad throttle position sensor. Of course this is the nearly $500 sensor but the multimeter indicated jumping resistance at a point above idle and ok at wot.

With a new fuel pump and tps the boat feels better than I can remember. Easy start, smooth acceleration and 6000+ wot.

Hope this helps someone else

I hate to hear that anyone ever has to replace the tps. It is stupid how expensive that little part is. More than Cadillac, & Mercedes (according to Rock Auto).