Major engine problems with 8 hp 4 stroke yamaha advice wanted

[dogridgekraus]

how far can they push it? rumors are about of an F450.
the 5.3L f350 is based on the European ford Taurus SHO motor.
the gearcase is already massive enough to handle it.
VVT is already on some of the late model inline 4 motors.
its always been VVT on the f250 and up.
the F70's operating range has been extended to 6300 RPM.
the ex on the new F115 has an external lung, looks like its going to be catalytic converter test platform.
with a few exceptions all inboard/sterndrive stuff made after 2010 will have cats and a fuel tank vapor recovery system.

yep 4 stroke outboard tech has come a long way from the old homelite bearcats of the 50's and 60's.

but yes I can see outboards with catalytic converters using pre and post cat O2 sensors and forced induction.

An F450...My gosh that would be a monster! Probably at a cheap 50K.lol...

The government just cant get enough when it comes to regulating...

Cats are very expensive & a pain with automobiles.They can be only 1-2% below threshold & it will throw the check engine light.Too bad the computors peramiters for that cant be "reseeded"a little wider.Now on newer cars they have an extra O2 sensor after the cat that has not other purpose but to monitor the status of the cat.
VVTI is a great advance but I can see all of this other sophisticated madness with emissions going into outboards to.I can forsee manufactures monopolizeing as car manufactures do & not enabling just any tech to perform work(dealor only crap).Its getting there fast! Sounds like its going to be more expensive.

[TownsendsFJR1300]

An F450...My gosh that would be a monster! Probably at a cheap 50K.lol...

The government just cant get enough when it comes to regulating...

Cats are very expensive & a pain with automobiles.They can be only 1-2% below threshold & it will throw the check engine light.Too bad the computors peramiters for that cant be "reseeded"a little wider.Now on newer cars they have an extra O2 sensor after the cat that has not other purpose but to monitor the status of the cat.
VVTI is a great advance but I can see all of this other sophisticated madness with emissions going into outboards to.I can forsee manufactures monopolizeing as car manufactures do & not enabling just any tech to perform work(dealor only crap).Its getting there fast! Sounds like its going to be more expensive.

Unfortunatly, there are good number of techs that don't keep up with the technology and often do more damage than good...

Its happened on my own F150 and on three of my older motorcycles that were still under warranty. The F150, with a low idle, (occassional stall-not unusual for that engine from the factory). They replaced the entire throttle body assembly(over $1,000 and of course was NOT the problem) and later screwed up the smooth idle as I watched them tune it out. I had to find a Master tech at another shop and he was able to tune the smooth idle back in.

Unless you have a trusted mechanic, the more YOU can do, the better...

The motorcycle world, IME, is probably worse than the marine industry.

[rodbolt17]

actually, like the auto industry, you will see a mandatory OBD language.
its already there for emissions con*****ed stern drives and inboards.
the Volvo EGC-E motors already have pre and post cat O2 sensors and have since 2010.
the EPA mandated that any hull manufactured for inboard/stern drive made after jan 1 2010 be equipped with cats and fuel vapor recovery for the fuel tank.
no more direct atmospheric venting.
same with portable tanks only the don't have vapor recovery,yet.
not much the average backyardigan can do with the latest F motors from any manufacture.
to many subsystems and to many TSB's and without factory support most will be limited to oil,filter and spark plug changes.
as of about 2011 all hulls with a built in fuel tank will have a vapor recovery system.
we just got a brand new 24 privateer to mount an F200 on and the system is mounted under the port gunnel.
not much is known about testing and troubleshooting of the vapor recovery system as so far its an aftermarket item not a Yamaha or engine manufactured item.
gonna be a learning curve.
typically the marine industry technology has
lagged the automotive by 20 years or so, that gap is closing rapidly.
the Volvo 5.7 cats are about 1100 a piece and typically require engine removal to remove and disassemble the ex elbow.
and they are NOT salt water tolerant.

[boscoe99]

Is it the camshaft that is timed to the crankshaft or is it the valves that are timed to the crankshaft?

Or, are valves timed to the camshaft?

The camshaft to crankshaft timing can be changed in some models.

Can the valves to camshaft timing be changed?

[99yam40]

should be able to, heck they even talk about cam less motors are being played with but not in production as yet.

Here is something to read on VVT
Variable valve timing - Wikipedia, the free encyclopedia

[boscoe99]

Let me rephrase one of my questions.

Does a Yamaha outboard motor employ variable camshaft timing or variable valve timing?

[rodbolt17]

as the cams turn at 1/2 the speed of the crank cam timing and valve timing are two ways to describe the same thing.
lets take the cams on the F150. same overhead cam design that the cam acutuates the valve directly with no rocker arms or followers. the cam actually pushes directly on the valve assy.
the cam drive sprocket is keyed to the crankshaft.
the cam driven sprockets are pinned(indexed,timed) directly to the cam shaft.
cam or valve opening is now fixed and can never vary from the crank until something breaks.

now we go to the F250.
the drive sprocket is again keyed to the crank.
the driven sprockets on all 4 cams are pinned to the cam.
once you figure out how to make the marks on the belt line up with all 5 marks on the sprockets AND the marks on the sprockets all line up with the respective mechanical marks the cams are now timed to the crank.
thus intake and ex valve timing is fixed to the piston location at any given point in the crank rotation.
valve actuation is the same as the F150,the cam acts directly on the valve assy.

now the curve ball.
the F250,and other Yamaha VVT engines.
has 3 cam sensors.
two on the intake cam and one on the port ex cam.
this,along with the CPS setup that's intragal with the stator/reluctor allows the ECU to know where the cams are in relation to where the crankshaft angle is.

the intake cam driven sproks are two piece oil pressure con*****ed.
at rest such as engine start the cam sprockets are at the full retard position.
once the engine starts and oil pressure is avalible the engine ECU looks at the varios sensors concerning engine speed,engine load and throttle position and throttle request.
as needed the ECU via oil pressure control valve solinoids and apply oil pressure to either side of the intake driven sprocket that is pinned to the cam.
this can move the actuall cam in either direction depending on ECU signals to the control valve.
in this method the ECU can vary the physical relationship of the intake cams to the crankshaft at any given time and still know where the cam angle is.
out of memory best I recall the ECU can advance or retard the cam about 28*,may be 23*.
air mooooves rather slowly and everytime that intake valve closes it comes to a dead halt.

by advancing the intake cam timing it allows a faster air ON time in relationship to piston travel.
this assists in the RAMMING effect of that long tuned intake air runner.

uses the mass of the air moving behind the intake above the throttle plate to fill the air charge.

its also why the VVT engines after an oil change or prolonged sitting or powerhead/cyl head replacement rattle like a mad dog for the first 10-20 seconds of starting.
so for this purpose valve timing and cam timing are the same.
we wont go into cam lobe separation angles nor lifts and durations because in this design they are fixed and part of the machined cam.

over the years we either fixed cam timing 3-7* BTDC and or used rhoades lifters to allow longer duration and higher lifts at low speeds yet still get the advertised lift and duration at higher speeds.
that way we could still us AC,powersterring and power brakes.

the Yamaha VVT system ,so far, can physically alter the relationship between the crankshaft and the intake cam shaft.

[boscoe99]

Yamaha refers to their system as VCT. Variable camshaft timing.

I propose that it is the camshaft(s) that is/are being timed to the crankshaft in a variable manner. In those models that offer VCT that is.

The position of the valves with respect to the camshafts does not change. The valves are just doing what the camshafts are telling them to do. The valves are not varying. Only the camshaft(s) is/are.

In automobiles there is a term referred to as "degreeing a cam". That procedure refers to the camshaft being set in a certain phase with the crankshaft. If there is variable valve timing(VVT) then why wasn't "degreeing a cam" referred to as degreeing a valve?

Another way of thinking about it is, which changes first? The camshaft or the valves? If there is .020" of clearance between the camshaft and the valve lifter, seems that it would have to be the camshaft.

[rodbolt17]

in both VCT and VVT its the cam shaft that is manipulated.
the valves are set in the head and cannot be easily manipulated.
you could vary the actual motion by increasing or decreasing lash a minor amount,maybe .020.
after that your not going to be able to keep the mechanism on the cam opening and closing ramps.
the automotive world has had vct or vvt whatever, for over 20 years.
the outboard world maybe 10 yrs.
valve timing and cam timing mean the same thing.

its a reference to where the cam opens the valve,typically at .050 lift vs where the crankshaft actually is.

its also why its not done on signle cam engines.
its been tried in the past but the ex typically doesn't want an advance.

the intake valve opening is advanced to take advantage of the 14.7 mile high colum of air trying to fill the space the piston is leaving as it moves away from top dead center and heads to bottom dead center.

the cam is actually a set of complex angles.
you have the base circle.
this is where lash is set,typically .008-.012 on Yamaha.
then you have the opening ramp,this is a fairly shallow angle to allow a softer contact with the shim pad before rapidly opening the valve.
then you have the nose which determines how long the valve is held fully open.
then you have the closing ramp that is a bit different to slow the closing valve down slightly to reduce seat banging and valve bounce at High RPM.
the cam profile for various designs are quite different.
some overhead cam motors used a cam follower similar to a rocker arm.
some used shaft mounted roker arms and a mechanical lash.
some,like most larger Yamahas us the cam directly on a wear pad that is sitting on a cap that rests directly on the valve stem.
the wear pad is also a shim to adjust valve lash.

the last method of valve actuation has been around almost 100 years,maybe even longer.
its very simple,very effective and very very lightweight.
just as with the piston/rod assy the valve,and valve train if applicable MUST go from a DEAD stop to maximum acceleration and back to a DEAD stop.
added mass simply means added stress.

unlike the 5.7CHEBBY roller cam 350 HP engine, the overhead cam desighn that the cam directly operates the valves has many advantages.

the 5.7 uses roller lifters,pushrods,rocker arms and then the valve.
the rocker arms actually swipe acrossed the valve tip in an arc creating a side thrust on the valve that can wipe out the stem, it happens.
the overhead design used by larger yamahas eliminates valve stem side thrust by using a shim cap or "bucket" that rides in a bore.
the cam acts on the bucket that is sitting on the valve stem.
this allows a straight down push as the bucket is accepting the wiping motion of the cam.
once again,the 5.7 must accelerate the lifter,pushrod and rocker arm AND valve from a dead stop,to its WOT and back to a dead stop without mechanical bounce.

even ole Newton knew for every action there is an equal and opposite reaction.

I am hoping to get to Volvo school this year for the new VVT 400 HP catalyst motor.

[robert graham]

I'm gonna continue to take REAL good care of my simple old C90!.....hopefully she'll outlast me and I can avoid all this technical "progress"....

[dogridgekraus]

Major engine problems with 8 hp yamaha

Well heres the lowdown on what I started this thread on...
Its looked like its turned into a lot of interesting topics...
I did a tear down on the T8,I hope I these pics show up here in this thread.Not much good with computors...I hope they show up,Let me know what you think...
To do it right it would take a crank & a rod for sure...
Maybe I could have the crank repaired though...If done right I think it should hold up...
Not 100% sure why just #1 rod failed? Obviously oil starvation.#2 is down lower so maybe that's why it is ok yet.The mains look ok.
Marty


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[rodbolt17]

check with Outboard Crankshaft Company,OCC and Carolina machine and tool in Wilmington NC.
at one time both companies welded up and reground two stroke cranks.

[TownsendsFJR1300]

All your pic's showed up. if you double click on each one, they get larger.

I'm surprised that crank isn't more torn up...

Amost missed the crack in the pan...

[99yam40]

Dang I was thinking this thing had a pressed together crank.
Must have thought it was 2 stroke, sorry about that.

Very good question as to what would keep oil from only one rod.
Spun bearing that blocked off oil hole is only thing I can come up with at this time.
Apparently there was oil to everything else or there would be more things damaged

[dogridgekraus]

check with Outboard Crankshaft Company,OCC and Carolina machine and tool in Wilmington NC.
at one time both companies welded up and reground two stroke cranks.

Thanks Rodbolt ill keep that in mind...I may have to go that route yet...
I brought the crank to a local engine builder today & am going to have him check the cranks runout.It one his concerns since you can see it did get hot there,he said hes seen them bend sometimes when they get hot like that,he said.
Other than that(just by looking at it)he said a lot of what I think it grooves that im seeing is from the rod & I may be able to just polish it off & get buy that way.
Thanks!
Marty