F90TLR 4 Stroke idles fine but won't get up to speed

[bgedwardsfour]

This is a 2005 F90TLR that is idling fine, will run at low speeds (8 to 10 mph), but will not go any faster with the throttle wide open. I have emptied and rinsed the gas tank with fresh fuel, put all new fuel in, replaced the large (oil filter sized) in-line gas filter, replaced the fuel filter on the engine and nothing has made any difference. With the engine out of the water, using the nuetral button on the throttle it will go from idle to full RPMs with no problem. Please help!

[CatCam]

Had a similar problem on a F115. Primer Ball was the culprit, it was collapsing as the fuel demand increased. Something (cheap) to take a look at.

[99yam40]

Check to see if some alarm is keeping motor from advancing the timing(safe mode).
If you have good compression, spark, & timing look at the fuel pressure /vacuum to see if there is a problem with delivery
Motor needs more fuel under load to produce power, maybe you just need to clean carbs

[bgedwardsfour]

Thank you CatCam and 99yam40. I will try what you have recommended and report back.

[bgedwardsfour]

The primer ball was not the problem though I did get a little improvement. I can get to about 3000 RPM and no more and it is not enough to get the boat on plane. I am checking fuel pressure and vacuum.

[madharchod]

i would be checking the TPS as if that's faulty it will do as you are saying but will not get speed when put in gear ,in neutral it will work fine and rev but under load it will shit itself ,sometimes the wires also get corroded at the terminals due to condensation so i will check on to that as well too
cheers

[TownsendsFJR1300]

Has the engine sat for any lenth of time, NOT run, WITHOUT ANY FUEL STABILIZER?

If so, and you do have carbs, its very likely the carb jets are gummed up with varnish.

Fuel goes foul in as quick as a month without a stabilizer. Draining the carbs(if equipped) into a small can (I use a tuna fish can) may show debis in the float bowl. You'll also be able to smell if the fuel went bad.

[bgedwardsfour]

I can't find a part called the TPS. In the Intake 1 parts diagram for 2006 F90TLR #6 is a Throttle Sensor Assy. Is this the TPC? I will check the electrical connections today.

Also, this is a fuel injected engine (no carbs). I have found 3 more fuel filtering devices. There is an in-line strainer going to the fuel injection pump, a filter inside the fuel injection pump and an in-line fuel filter on the intake. Could any of these be limiting the amount of fuel to the injection system?

[rodbolt17]

any and all of the above.
also each injector has a filter.
electrical issues on that motor are scarce as hens teeth.
fuel buggers get all makes.

I haven a customer now that is mad at Yamaha.
his fuel vent sucks water.
he ran the engie,F150, until so much water had accumulated in the VST that it quit running.

now 4 cylinders are rusted and 8 out of 16 valves are stuck open.
he is mad cause Yamaha isn't going to cover HIS bad fuel system under warrenty.

90% of the work I do on EFI 4 strokes is fuel related.

[bgedwardsfour]

Solution to not being able to get the 2006 F90TLR up to full power

This is a 90 fourstroke with electronic fuel injection. The boat would idle and also run at about 8 to 10 miles per hour, but did not have enough power to go faster. After cleaning out the gas tank, replacing the large in-line fuel filter, replacing the fuel filter on the engine, and putting a stabalizer and cleaner in the fresh gas, there was only a small improvement.

I went to YouTube and found a video on how to remove the injectors. It turns out the injectors have a fine mesh screen on them. I soaked the injectors in carb cleaner and sprayed the screen side and the nozzle side of the injector with car/choke cleaner and installed them back in the engine. Taking the injectors out and putting them back is easy.

Problem Solved! The engine gets up on plane and runs a 40 mph with no problems.

[CatCam]

good news!

BTW - If you don't have a 10-micron inline fuel filter I would seriously consider installing one. Not a guarantee but is one more hurdle that could keep your fuel system clean. Seems that 95% of our outboard problems are fuel related. Take care and happy boating!

[bgedwardsfour]

Thanks CatCam. I do have a 10 micron (oil filter sized) in-line filter between the tank and the primer ball. This was a good learning experience. I learned a lot of valuable information about the engine in the process.