4 Stroke Yamaha 90 jet

[money pit1]

I got an 05 Yamaha EFI 4 stroke jet I bought a few weeks ago that had set for a year or so due to his health. I put it on a 17x56 allweld jon boat and ran it fine for 2 or 3 trips of 5 to 7 miles. Running up river last trip it was losing power so loaded it up. Called local dealer it was bought from and started looking for the things he said to look for. I pulled jet and checked bearing and shims looked good, replaced fuel filter on back of motor and added a 10 micron inline filter, Pulled injector fuel pump housing and cleaned looked like sand out of it and sent injectors to shop and had cleaned and tested and talked to person that did work and said they was somewhat dirty but not enough to stop flow. Test report shows all working good from start to finish. Checked injector fuel pump with pressure test and had nothing there. Change fuel pump 300 bucks and cleaned housing and took down to test run samething no top end power. Changed spark plugs and throtle cable in hopes but samething there. Have checked throtle sensor with ohms and was reading good. I'm at a loss on this thing. Have been reading up on e10 fuels and don,t know if that might have something to do with it. Will put additives in fuel from now on. Any ideas will be greatly used to get back on the water. Going to take it back to dealer motor was bought from and see what he thinks after holidays.

 

[rodbolt]

Re: 4 Stroke Yamaha 90 jet

double check fuel rail pressure at the problem RPM and load.
also check the jet muffler,pinholes,corrosion or not seated can and will cause a lack of top end.

 

[money pit1]

Re: 4 Stroke Yamaha 90 jet

Tried it all over 1 more time. I called local yamaha dealer motor was bought from and after talking some he has mentioned something on the pump housing being in "phase 2" and something along the lines of the housing is made in japan of cheaper quality materials unlike his mercury line made in the usa. I have been machining pars for 25 years and I know there is a difference where you get materials but somehow I would think that if this housing is doing something and leaving crap in the housing someone out there would be having the samething and I'm sure as big as Yamaha is they would do something to right this thing with there customers. I am going to get injectors 1 more cleaning and go thru housing and check everything and see where it goes before taking it to dealer to sell me new injectors.

 

[rodbolt]

Re: 4 Stroke Yamaha 90 jet

your dealer is a christmas turkey.
instead of tossing parts and pieces at this motor why not simply trouble shoot it and fix it.
its an incredibly simple speed density open loop EFI system.
electrical failures are very rare as are mechanical ones.
mostly EFI issues are fuel related,especially when they get neglected.
yes mercury and yamaha hd some joint ventures,no the F90 was NOT part of it.
some of the merc F115,F200 and F225 were yamahas with a black dress,some of the F40 and f25 were mercs in a silver blue dress.
that ALL ended in 2003 or so.
go find a real dealer.
clean the VST,send the injectors to flagship,check fuel rail pressure AT the problem RPM and load.
no where in the Yamaha manual does it mention an ohms test for the TPS,only voltage.
that TPS is also self learning.
but fix your fuel issues,its not a yamaha issue.

 

[money pit1]

Re: 4 Stroke Yamaha 90 jet

After reading up on all the 4 stroke troubles. got to thinking about all that was done and not knowing what had been serviced on the motor I drained oil and changed filter and it runs like a champ got 6 hours of good run time in yesterday. Thanks for all the help.

 

[99yam40]

Re: 4 Stroke Yamaha 90 jet

I do not understand how a oil and filter change would fix the problem

 

[rodbolt]

Re: 4 Stroke Yamaha 90 jet

whats even funnier is that merc dealer failed to mention that now mid range HP mercs are built in a state of the art manufacturing facility,where?
wait
wait
wait
CHINA
merc built a 300 million dollar plant and is building another.
I hope the guys in fon du lac like fisheads,chicken feet and rice.

 

[Don S]

Re: 4 Stroke Yamaha 90 jet

Here is the company that manufacturer for Yamaha jets and jet parts.

http://www.outboardjets.com/contact.php