Major engine problems with 8 hp 4 stroke yamaha advice wanted

[boscoe99]

If you work on automobile motors, and have an open mind and are willing to read and learn, then you can work on outboard motors. There are more similarities than there are differences. There is no rocket science about any of this.

One thing you will find with Yamaha is that if a crankshaft or camshaft is undersized there is no mention of the use of an over size bearing with it nor is there any mention of having the crankshaft build back up and reground to proper dimensions. This is a throwaway world now. I suspect that you could find a machine shop to do it for you anyway if it makes economic sense to do so. The smaller the motor model the less economic sense it will make.

Good luck an enjoy your project. It can be fun.

[dogridgekraus]

next time your chatting up with your race car bubbas.
ask them about an issue with your chevy.
make sure you tell them it only acts up after 15 min or so ABOVE 5000 RPM.
that's the difference.
other than that, its just a high performance machine.

I don't think its good for any motor to run above 5K.
Even on my boat with the main outboard (Merc 150 XR6) I don't cruise at that rpm.At that rpm the forces/stress is really high.
I don't think this Yamaha was meant to run like that.Its a kicker motor yaknow & a 4 stroke at that.
I would say 4 stroke outboards have to be built to withstand at lot higher rpm than most automobile engines.But there still 4 strokes.Nothing like the rpm loveing 2 strokes.

Maybe I should just scrap the whole thing then & take my lossed while im ahead...IDK...
From what im getting here is it wont hold up otherwise...
Do you know where I could l look for a good used powerhead other than ebay?
Well Thanks:
Marty

[99yam40]

why even look for parts until you fine out what is wrong with yours?

The 4 stroke outboard motors need to run close to upper RPM band, but may not be good to do it all the time.
If you lug them and run at low RPMs too much it will end up making oil

[dogridgekraus]

If you work on automobile motors, and have an open mind and are willing to read and learn, then you can work on outboard motors. There are more similarities than there are differences. There is no rocket science about any of this.

One thing you will find with Yamaha is that if a crankshaft or camshaft is undersized there is no mention of the use of an over size bearing with it nor is there any mention of having the crankshaft build back up and reground to proper dimensions. This is a throwaway world now. I suspect that you could find a machine shop to do it for you anyway if it makes economic sense to do so. The smaller the motor model the less economic sense it will make.

Good luck an enjoy your project. It can be fun.

I agree,well put.Sounds hopefull anyways.
As far as the crank goes that's the way its looking.
As much as people spend for there outboards they should be more service friendly.They build great outboards but they get a thumbs down from me.Its BS! So,so much for luck,chances are im screwed...
I guess ill find more out when I do a teardown.
Makes me hate to invest another $70 for a service manual for it since I may have to just end up going a powerhead instead & I don't know if ill get my moneys worth out of having the manual since I don't rebuild outboards frequently ETC.
Thanks:
Marty

[dogridgekraus]

why even look for parts until you fine out what is wrong with yours?

The 4 stroke outboard motors need to run close to upper RPM band, but may not be good to do it all the time.
If you lug them and run at low RPMs too much it will end up making oil

I just wanna know what im getting myself into first.
If you heard the outboard you'd know theres something major wrong.
I haven't even torn it apart & can get some silght vertical movement out of the crank by just grabbing it & pulling it vertically back & forth.
You can see on the inside of the flywheel where its rubbed the windings (for the charging syaytem) on the inside of it.
So without even tearing it down Id bet the main journals may be spun or totally shot.Cant be very promising to still have a good crank out of the deal.

As far as a four stroke "making oil" ive heard of this scenario before but never understood it? That's how I would be useing it for the most part(as a kicker)
for *****ing.
I wish I could hear some good news on here.lol.
Thanks:
Marty

[almetelo]

I wish I could hear some good news on here.lol.
Thanks:
Marty

What about the SM ? would be a good news for now? lol

I guess I have it on my data but just can check that tomorrow at home as I'm working till tomorrow morning.

If I have it I'll post it here for you and you can save a "few" bucks

[dogridgekraus]

What about the SM ? would be a good news for now? lol

I guess I have it on my data but just can check that tomorrow at home as I'm working till tomorrow morning.

If I have it I'll post it here for you and you can save a "few" bucks

SWEET
Thanks Almetelo;
Marty

[boscoe99]

Almetelo is a good man.

Merry Christmas to him and you lowly curmudgeons.

Even to our chief curmudgeon.

[TownsendsFJR1300]

Marty,

If you have a Leak down tester, before you pull the top end off, it'll give you a good idea of the condition of the top end...

Agreed, up and down play on the crank is NOT good, (same as excessive for aft and play on an auto engine).

Depending on how much you have into the engine, you can see used parts are NOT generally cheap.

You may very well get most of your money back "parting" the GOOD parts of the engine out. A good block, lower unit, etc can fetch a couple of bucks...

Just a side note, I grew up on the old Yamaha 2 stroke YZ's, etc..Pulled many apart down to the crank / connecting rod bearing, etc too.

Fours strokes have come along way since the 1970's. My current Yamaha motorcycle, a 600cc, 100HP, red lines at 14,000 RPM It doesn't "wake up" until 8,000 RPM, then hang on..

And as Boscoe pointed out, its a 4 stroke engine(or easier yet, a 2 stroke). Nothing magical about it. Like any engine, it'll have its different sensors, etc on it but the internals are still piston(s), rings, crank, etc..

As noisy as it is, you likely don't need a dial indicator(nor a manual) to see 1/4" play in the rod end, etc, is bad...

[rodbolt17]

and that's the auto bubba bubbling over.
that engine will turn 5500 RPM longer than your bladder will allow with no issues.
the issues start when you try it with bad fuel, nasty carbs, incorrect linkage adjustments and MOST critical a degraded cooling system.
unlike inboards and sterndrives that typically used a marinized automotive type motor these motors were designed to go.
the pistons on the F250,F115 and the rest are works of art.
it used to take us HOURS with a grinder and a scale making our own "slipper" skirt designs.
with a slipper skirt design piston to wall clearance is CRITICAL.
that's why most production auto engines did not use it.

that F8 doesn't appear to have any seperate thrust bearings.
you should not need a manual for teardown.
you will for inspection and reassembly.
it is a very high performance little tiny mite that is designed to operate between 5000 -6000 RPM and its recommended to prop it at 5800-6000 for its load that day.
otherwise it tends to get hard on bearings,pistons and valvetrain due to lugging.
even if its your kicker it MUST be able to kick along at 5800-6000 RPM with the hull and gear and persons onboard that day.

I do have a1998 T9.9 25" electric start kicker that will be for sale in a week or so.

[almetelo]

Hi!

Here you have the SM for your motor

https://drive.google.com/file/d/0By0...ew?usp=sharing

Hope this can help.

Merry christmas for those who celebrate the season, for those who don't... happy holiday!

[dogridgekraus]

Marty,

If you have a Leak down tester, before you pull the top end off, it'll give you a good idea of the condition of the top end...

Agreed, up and down play on the crank is NOT good, (same as excessive for aft and play on an auto engine).

Depending on how much you have into the engine, you can see used parts are NOT generally cheap.

You may very well get most of your money back "parting" the GOOD parts of the engine out. A good block, lower unit, etc can fetch a couple of bucks...

Just a side note, I grew up on the old Yamaha 2 stroke YZ's, etc..Pulled many apart down to the crank / connecting rod bearing, etc too.

Fours strokes have come along way since the 1970's. My current Yamaha motorcycle, a 600cc, 100HP, red lines at 14,000 RPM It doesn't "wake up" until 8,000 RPM, then hang on..

And as Boscoe pointed out, its a 4 stroke engine(or easier yet, a 2 stroke). Nothing magical about it. Like any engine, it'll have its different sensors, etc on it but the internals are still piston(s), rings, crank, etc..

As noisy as it is, you likely don't need a dial indicator(nor a manual) to see 1/4" play in the rod end, etc, is bad...

I agree I think ill pass on thinking about a manual till I do a tear down & save myself $70 for now.
I don't like having an engine im not familiar with removed & tore down.If possibly I am fortunate enough to do a satisfactory economical repair.Then remembering at a LATER date can be confuseing.Im talking the wireing routing of everything ETC.Id almost have to have a manual then.
To me parting out is not a sure thing...Pros & cons I guess...
Yeah it has a good starter, charging system, power trim & tilt,lower unit,ETC.
But really being able to market & actually SELL all of those parts.Is not a guarantee.As I already have $800 in it also. If I was to start to part it out & sell say 1 of anything I mentioned then im stuck with parting it out.
A complete running unit would be easier to sell id think.IDK...I hope I don't end up going that route.
Four strokes have come a long way in every way.Technology is great...I just wonder how much futher they can push the limits.
VVTI( variable valve timing intelligence) On some of the Toyotas ive driven has really taken performance to a new level.Insane rpm & a long torque curve.
Not as insane as your bike but really impressive.
Yamaha actually builds some of the heads for Toyotas.
Merry Christmas!
Marty

[dogridgekraus]

Hi!

Here you have the SM for your motor

https://drive.google.com/file/d/0By0...ew?usp=sharing

Hope this can help.

Merry christmas for those who celebrate the season, for those who don't... happy holiday!

Gosh,Thanks Almetelo! I think that's the best Christmas present ive received yet!lol
I beginning to think id never come across one online.Your a big help!
Merry Christmas to you:
Marty

[dogridgekraus]

and that's the auto bubba bubbling over.
that engine will turn 5500 RPM longer than your bladder will allow with no issues.
the issues start when you try it with bad fuel, nasty carbs, incorrect linkage adjustments and MOST critical a degraded cooling system.
unlike inboards and sterndrives that typically used a marinized automotive type motor these motors were designed to go.
the pistons on the F250,F115 and the rest are works of art.
it used to take us HOURS with a grinder and a scale making our own "slipper" skirt designs.
with a slipper skirt design piston to wall clearance is CRITICAL.
that's why most production auto engines did not use it.

that F8 doesn't appear to have any seperate thrust bearings.
you should not need a manual for teardown.
you will for inspection and reassembly.
it is a very high performance little tiny mite that is designed to operate between 5000 -6000 RPM and its recommended to prop it at 5800-6000 for its load that day.
otherwise it tends to get hard on bearings,pistons and valvetrain due to lugging.
even if its your kicker it MUST be able to kick along at 5800-6000 RPM with the hull and gear and persons onboard that day.

I do have a1998 T9.9 25" electric start kicker that will be for sale in a week or so.

Your definentally right,I need to know that it will run that rpm as its rated for since just having it on my boat as a *****ing kicker isn't the only reason its on there.Lets say im 4-5 miles out on lake erie & my main outboard decides to have a bad day.At least ill have a way back then! lol...
I guess your T9.9 is an extra long shaft then?
My application calls for just a long shaft.I guess longer wouldn't hurt though..
I thought the T6 & T8's were lighter in weight as that's a concering factor for me witch im unsure of.
The boat I have is a 2001 Triton 189 DCF.It did have an 03 merc 4stroke as a kicker but the seller refused to include it with the sale.I know the older merc 9.9 is on the heavy side.So I thought just a little lighter kicker would help with performance losses.Though I don't know since I haven't ran it with one yet.
I thought my search had ended for a kicker when I found this T8.
Im not sure if I need to worrey about the weight factor of an extra kicker or not for my boat? Heres a link to walleye central of a few pics of my boat that may give you an idea.

Walleye Message Central - mk27011@yahoo.com's Album: 01 Triton 189 dcf

I think a twin cylinder 4 stroke is the best option for smoothness,yamahas the only one I know that builds a twin 6hp.
With a smaller outboard IDK if I would get the adequet performance as these high thrust versions are made for.Im so undecided about everything if you haven't noticed.lol
Merry Christmas Rodbolt:
Marty

[rodbolt17]

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.