HELP PLZZ!! 2001 Islandia Merc 240hp EFI runs on shore but not in water!

[harley dad]

Hello all and thank you for any help you may have.
Ok so hears what I have. She will run on hose no problems at ANY RPMs for any length of time.
But when I put her in the water she will idol fine and even come up to around 3000rpms
but after that she will seem like she is maybe starving for fuel or something and just shut down like the key was turned off.
She will start right back up and have no problems at all idling or coming up to 300rpms.
She has new fuel pumps and filters new oil pump , reed boxes , plugs and coils.
She has over 110psi compression over all 6cyl and 35psi fuel pressure.
Water flows out the pisser.
Not sure if there is a bad sensor or switch that my be telling her to shut down.
I had a EFI boat (not a see-doo) that had a bad oil pressure switch that made the boat never go over 3500rpms and it drove me crazy till I found it.
Any thoughts or ideas would be great!
Thank you!!!

 

[Tim75]

Hello all and thank you for any help you may have.
Ok so hears what I have. She will run on hose no problems at ANY RPMs for any length of time.
But when I put her in the water she will idol fine and even come up to around 3000rpms
but after that she will seem like she is maybe starving for fuel or something and just shut down like the key was turned off.
She will start right back up and have no problems at all idling or coming up to 300rpms.
She has new fuel pumps and filters new oil pump , reed boxes , plugs and coils.
She has over 110psi compression over all 6cyl and 35psi fuel pressure.
Water flows out the pisser.
Not sure if there is a bad sensor or switch that my be telling her to shut down.
I had a EFI boat (not a see-doo) that had a bad oil pressure switch that made the boat never go over 3500rpms and it drove me crazy till I found it.
Any thoughts or ideas would be great!
Thank you!!!

Welcome.

Your Merc engine does not have any "oil pressure switch" that could limit rpm. There is only a float switch in the oil header tank. It only turns on a beeper that tells you are low on oil.

What is your idle rpm on land and in water? Should be about 1200 on land. Running the engine onland above 2500rpm is potentially dangerous (for the engine). It can easily overheat and melt a piston.

Compression:- 110psi is somewhat low. Was it checked with all plugs out, full throttle, on land, with a fully charged battery? If not, that could explain your low numbers. Should be 140psi.

Do you have the dreaded throttle guardian in helm box next to fuse block? They can cause several different issues. Find black with yellow stripe wire and cut it about 4 inches from the box. Seal both ends. This will take the TG out of the circuit.

While your engine is at 3000rpm (in the water of course), what happens if you jam the throttle wide open? Does it die or stumble and rev up to at least 5500rpm? Check that you have spark on all six.

Have you checked your trigger? 3 pairs of wires coming out from under flywheel, starboard side? Have you checked the tps? Starboard side, down low, on end of bottom throttle shaft. Specific instructions in service book. You are going to need it.

Has this boat sat for a long time without running? You could have fuel injector issues, also.

 

[harley dad]

Thank you very much for the help.
Can not say what the rpms are for land and water as of yet (bringing the boat to the ramp every time I need to test her is not that easy ).
I do have spark on all 6cyl.
Boat was used last year but not this year do to this prob. I just bought the boat from the previous owner
after he spent over $4000 at a (non see-doo/non Merc specialist dealer) and it still did not work.
The compression test was not done at WOT. thank you for that info I will retest.
I will check the other things you mention when I get home later today

Thanks again !!!

 

[Storage]

...Good Luck fixing this problem, as my 2003 had almost the identical problem, but
at 2,300 rpm's. Over last 2 years has been at TWO different Boat repair yards, sitting for 8 months...
BUT No-Body can repair my boat. It ran fine in 2018, then 2019 season ... this Limited RPM problem!
Just sits in my yard, as a "Yard ornament"! I have one other Boat Shop about 3 hours away
that I am thinking about taking it to him, and see if he can fix this issue over the Winter season!
New Fuel ... New Battery ... New in pre-filter .... New Large Filter .... injectors cleaned .... Computer
shows No-Issues ..... Starts... Immediately with Every 1 second turn of Key!
I HATE Sea-Doo, and Mercury........ can't repair their equipment/Boats they SELL!

 

[Tim75]

Thank you very much for the help.
Can not say what the rpms are for land and water as of yet (bringing the boat to the ramp every time I need to test her is not that easy ).
I do have spark on all 6cyl.
Boat was used last year but not this year do to this prob. I just bought the boat from the previous owner
after he spent over $4000 at a (non see-doo/non Merc specialist dealer) and it still did not work.
The compression test was not done at WOT. thank you for that info I will retest.
I will check the other things you mention when I get home later today

Thanks again !!!

Leave the boat on the trailer in the water with the stern still tied down. Open hatch to engine. Ear muffs are a good idea. Bring the rpm up to where it stumbles and check the spark again.

It is sounding like you have a bad trigger, under the flywheel. The proper puller is about $40 on ebay. Visual check the 6 wires from the trigger. The old original triggers had crappy wire whose insulation would crumble over time and cause all kinds of issues.

Some Merc dealers are helpful. Some are rip-off shops. ALWAYS get your old parts.

When you check the spark plugs, do they all look the same? I always wory about injectors on a 21 year old engine. It cost me $130 to have all 6 tested, cleaned, matched, tested again. Money well spent. 6 new is about $750.

 

[Poormanracing]

Check the pin connectors that plug into ECU had a few of these turds do the same thing but intermittent.when it's running start moving some harnesses and wires close to the connectors and sensors.see if engine cuts out.this one drove me nuts to find.ended up up getting rid of the I think it's was a 12 pin connector and just hard wiring it on two oof the boats.if not successful bring it to a Merc dealer.all they are is a 240 efi all they need to do is plug a Merc test harness in and run it.