Hello and question about my YAMAHA F250

[f250fan]

Hello to iboats.com users. I have to say, it seems like this web site has a lot more useful information than that other boating message board. Too much brand warfare.

I have a pair of Yamaha F250s with just over 725 hours on them. The motors run excellent. They idle smooth and have loads of power from idle to full throttle. WOT on the engines is 5800 to 6100 depending on load and conditions, and they hold WOT perfectly. Lately, after starting the engines, they will come up to warm up speed and then gradually come down to normal idle of 600 to 700 rpms. If you pull the cowling off of the engines, you can hear the injectors making their normal noise, and if you listen you can hear an audible tap. This is muffled by the cowling to the point that you can't hear it with the cover on, and also disappears upon advancing the throttle(even in neutral). There is no such noise when running the engine under load and when idling after running the engine under load to operating temperature you can pull the cowling and don't hear anything. I am thinking it is one of the injectors tapping a little more audibly, but would like to eliminate the possibility of a valve tap. However, as these are DOHC motors where the camshafts ride directly on top of the valve buckets(no rocker arms to tap against the bucket?) I wonder what would actually tap??? Excessive valve train noise that I've heard in DOHC import motors often makes the motor sound like a diesel or more of a 'clacking' sound, and this doesn't sound like a diesel or clack....just a tap that is slightly more audible than the injectors, disappears with an increase in RPM's, load, and warm up.

Any thoughts? Thank you.

 

[rodbolt]

Re: Hello and question about my YAMAHA F250

best I recall valve clearence check and adjust was part of the routine maint at either 400 or 500 hours.
was it ever actually done ?

 

[maxhp]

Re: Hello and question about my YAMAHA F250

Gave wrong e-mail address for other username and can't remember password...

rodbolt, motors have not had valve clearance check/adjust...I'd imagine that's a costly endeavor having to remove the valve covers and check the clearance with feeler gauges and shim to spec if needed??? Went back to boat today and did thourough inspection...tap is definitely eminating from injectors...injectors do make some noise on these motors, but they run excellent. Only noise coming from valve covers is a continuous, quiet mechanical noise that is probably the cams rotating on the buckets...agree? Took the motors out and pinned the throttle and went screaming across the harbor at a super smooth 6000 rpms. I love those things...if the valve train needed adjusment I'd think you'd know it at high speed?

Also, my engines on COLD start up sometimes idle irregularly for a couple of seconds. They then run perfectly smooth at all speeds. Upon start up, they'll crank up to 1400 or so, drop immediately to 5 or 6 hundred, and then bounce back to 900 or so for warm up when they drop to 700. Once through that initial couple seconds they run great. Have seen a couple other late model f250's do it, too. Doesn't effect how they run, and it's only a couple seconds. Hooked up to laptop and everything is normal. Cleaned throttle valve, no change. Have noticed it happens more often during slow times at marina...so I am assuming maybe the octane drops from fuel sitting and it takes engine a second or two to adjust for it? These motors are 2008's. I did notice on a set of 2006 motors that when they start up they initially rev to 2300 and then drop to 900? Like I said, my '08's only run to 1400 on start up? Where should they be?

 

[rodbolt]

Re: Hello and question about my YAMAHA F250

sounds about right, all the way down to a customer not wishing to spend a dime till it absolutly trashes itself then whine about the product.
while its not cheap to have the lash checked and its rather rare to have to adjust anything the procedure for lash checking can be done by most anyone with a 5th grade reading comprehension level and the correct service manual.
adjusting the lash requires some training and general knowledge of dual overhead cams and the variable cam timing system.
next time you hook a tach to your EFI car look at how it hunts for the first few seconds.
the ECU starts the engine with sensors fixed and a cold start map.
takes a few seconds for the ECU to look at all the sensors and make corrections.
the F250 has a lot of stuff to look at and adjust and do it rapidly.
system actually works very well.
just like when I worked at a porsche mazda dealership.
customer would come in complaing about his broken timing belt at 80K miles.
ask when was the last belt change and the reply was always,never it always worked.
up until it did not.
price of the belt and the change stays the same cost of the head and associated labor rather jacked up the cost.
belt change intravel at the time was every 20K miles.
same as Yamaha ,belt change at 1000 hours OR 5 years whichever occurs FIRST.
never saw a belt failure on the F yamahas,yet, but I know they are coming as the engines age.
bad thing with the F250,and some others, is they are a double non clearence motor.
not only will the valves not clear the piston in the event of belt breakage the valves wont clear each other in the event of a belt failure.

 

[maxhp]

Re: Hello and question about my YAMAHA F250

rodbolt, I understand, but the cams/valves sound normal, so would you still check clearance if no noise? I can see if they were getting noisy. Never heard of a bit of valve noise trashing a motor? I do agree about maintenance. I am approaching 1000 hours and plan on doing the timing belt as it is an interference motor and will smash the valves if the belt breaks. At 500, did water pumps, t-stats, oil control valve filters(didn't look dirty at all), etc.

 

[rodbolt]

Re: Hello and question about my YAMAHA F250

most the problems I see with valve clearence is lack of.
as the valve seats recede the clearence gets to tight.
makes no sound until a valve cant seat then it burns the valve face.
the design of most modern high performance equipment makes it a pain to access anything.
that I understand.
belt change on the F250 is about a 6 hour ordeal.
I have a pair of F350's waiting when the shop reopens in january that I am dreading.
the water pump is annual or every 200 hours whichever occurs first.
but we see them last longer.
depends on the usage mostly.
here in our shallow salt pond sand tears them up quickly.
myself, I would most likly wait and check the valve clearence at the 1000 hr mark as your close to it anyway and you will be there at that time anyway.
thats a personall observation and in no way a reccomendation as its your motor.

 

[maxhp]

Re: Hello and question about my YAMAHA F250

Rod, here's a question for your experience level...

Buddy at my marina has a boat with twin F250's, 2006 MFG year. Mine are 2008 MFG year. He asked me to start his today and let em run. Fired em up and they turn to 2300 immediately after start up, then drop to 900 for warm up...typically, my 2008's turn to 1400 immediately, and then drop to 800 to 900 for warm up...which one is normal, or did something change on later model motors that they don't crank up as high on start-up?

 

[rodbolt]

Re: Hello and question about my YAMAHA F250

both are typical.
first F250 I ever lit off scared me so bad it got an immediate shut down .
no one warned us that its serious when you start it on a flusher .
since then I have scared many trainees and a few dock hands .

 

[maxhp]

Re: Hello and question about my YAMAHA F250

Rod, thanks for that. My buddies '06 models scared the bejesus outta me when I started them and they revved to 2300...startled me to death. My '08's are way more mellow on start up...

 

[rodbolt]

Re: Hello and question about my YAMAHA F250

yep, get a trainee thats never stated an older F250 have them fire it up on the flusher.
they are already nervous.
as soon as its starts, scream,throw your hands up and watch the fun .
more fun if you notify fellow techs of the fun.
some trainees will actually jump away from the console.
the F350 is as bad or slightly worse.
its way more intimidating than the F250.

 

[maxhp]

Re: Hello and question about my YAMAHA F250

Those 05 and 06 motors are screamers...

Did you ever need to do a valve adjustment on one of these motors? If you did, was the motor making any valve noise? Mine are whisper quiet with the cowlings on...the only thing you really hear is the pisser hole pissin in the water...the cooling water hitting the water surface is louder than the motor. I am guessing if your valves were making racket you'd know it with the cowl on...solid metal valve train seems like it'd be noisy if an adjustment was necessary if the valves were too loose...??? It seems like if I pull the cowl off and get down next to the motor and listen good to the valve covers you can hear the cams turning on the valves, but I am gonna go ahead and assume that if you need to put that much effort in to hearing anything, it's normal...

 

[rodbolt]

Re: Hello and question about my YAMAHA F250

so far on the F250,s I have checked no adjustment has been nessasary.
thats why I go to schools and will again from jan11-15th.
thats where we get to practice on live motors replacing belts and adjusting shimms as well as a lot of other good stuff we dont see in the field much, yet.