Major engine problems with 8 hp 4 stroke yamaha advice wanted

[dogridgekraus]

Hi,Im new to this site so I hope im in the right place & apologize in advance for my long discourse here...
To make a long story short...I just bought a used 2002 Yamaha 8 hp 4 stroke.
I made a big mistake in takeing someones word that it was a good motor & they said it would probably need only the usual minor work from setting a year.I thought it was a decent price for $800.I guess it would have been aside from the fact that it sounds like the bottom end is about ready to fly apart!
I feel like a fool & am very pissed...
Now I have to deal with it I guess.
I don't know what to do but I figure,I should just probably get it going again so its worth something?
I was looking into a powerhead on ebay that cost more than I paid for the whole unit I bought! So that has me thinking on trying to repair/rebuild.
Being it hasn't thrown a rod out the side of the block I thought it may be worth looking into trying that first.Beings I really don't want to have more than the outboard is worth in it.Maybe dreaming there...
I am a mechanic but not an outboard mechanic but willing to try.
Does anyone know where I could get a shop manual for it? Are they expensive?
So I guess Id have to remove the powerhead & tear it down & see how bad it is first.
I was looking at a crankshaft piston diagram & noticed that it doesn't look like there is any bearings for the rods on these?
There is bearings for the crank I can see.
Makes me wonder if my local engine rebuild shop could even do any machineing work to it?
Is there oversized bearing available for these?
What about the rods being it appears theres not a bearing,could it just be resized to the crank?
I know without tearing it apart that the main crank bearsings are fried since I can actually get a slight bit of back & forth movement out of it.Not good,I know..Might be spun IDK if the block could be re lined bored if that was the case? If machine work can be done it may be cheaper than a powerhead.
Maybe the oil pump may have issues to due to this,can they be taken apart & inspected on this modle?
2001 or 2002? modle T8PLRA
Any advice would be appreciated!
Thanks:Marty

[99yam40]

2002
Yamaha Outboard Parts

Yamaha crank is pressed together with the rod bearing installed.
Need some shop with proper jigs and other equipment and know how

Look up your manual # here
YAMAHA MANUAL STORE

and then look on line or just order it on that same web site

[dogridgekraus]

2002
Yamaha Outboard Parts

Yamaha crank is pressed together with the rod bearing installed.
Need some shop with proper jigs and other equipment and know how

Look up your manual # here
YAMAHA MANUAL STORE

and then look on line or just order it on that same web site

Thanks for the reply!
Sounds a little more complicated than I thought..When I looked at the parts diagram for the crank & piston assy. it didn't show any rod bearings.Wouldnt it have showed them if they were available or is a complte crank assy, the only way it comes? I figured it would show the bearings for the rods whether there pressed in or not.
I found a used powerhead for it for $425 but thought I may be able to get away cheaper just rebuilding it.
I already have $800 in it thinking it was a decent unit,really didn't want to get more in it than what its worth.But maybe that's the only way it will be worth anything.
It don't look like theres much to these small powerheads,whitch made me think I still might be able to come out of this ok,but maybe not.
I guess the only way to tell that is seeing what I got after I tear it down.
Just want to know what to expect & have the right direction to start before I do anything.
Thanks:Marty

[rodbolt17]

never had the F/T 8 apart.
a few F50 and a couple F250.
however its not uncommon to use a babbited rod on a ground crank journal on small motors.
briggs and Stratton,and a few others, did it for years.
I can tell you no undersized or oversized parts are avalible for the US market F motors.
unlike automobile type stuff you cant grind cranks or rods and fit under or over sized bearings.
don't ask me why.
they simply are not made.

[almetelo]

I can tell you no undersized or oversized parts are avalible for the US market F motors.
unlike automobile type stuff you cant grind cranks or rods and fit under or over sized bearings.
don't ask me why.
they simply are not made.

Not for US not to anywhere (at least on Manual Parts I´ve seen"

But why crankshafts and rods with "colour" bearings?

On the F40 that I lately bought on the crankcase and rods have the letter B that stand for BLACK bearings (A is Blue and C is Brown)

So what is the diference!? couldn´t get an answer so far...

Anything else to have in mind for when I'll buy the bearings?

I think Yamaha don´t having undersized / oversized bearings make crankshafts disposable which is "heart" of the motor (IMO) and very expensive...

At least here in EU don´t worth get a new crankshaft for a repair

dogridgekraus don´t want to take you the thread.

[rodbolt17]

as its not a perfect world any variation from perfect is a variance.
the bearing color selection is based on the actual measured varience.
the F250 has a bearing number on the crank for bearing sizes under or over nominal size.
the block is likewise stamped.
bearing selection can be a chore and plastigaging is mandatory at assy.

its kinda like the F,R and P numbers under the trim tab.
they are a measured variance from a perfect case.

can the crank be welded and reground? most likely.
could the block be shaved and the bearing bores rebored? most likely.
however the machine work would most likely cost more than a new powerhead.

[dogridgekraus]

never had the F/T 8 apart.
a few F50 and a couple F250.
however its not uncommon to use a babbited rod on a ground crank journal on small motors.
briggs and Stratton,and a few others, did it for years.
I can tell you no undersized or oversized parts are avalible for the US market F motors.
unlike automobile type stuff you cant grind cranks or rods and fit under or over sized bearings.
don't ask me why.
they simply are not made.

Im not sure I know what you mean by a "Babbited" rod?? A rod without a bearing like I saw in the diagram? I figured it could possibly be resized to the grind of the crank...Sorrey if im asking why.lol. Maybe im just screwed here.
Having a mechanical background (automobiles) I thought it could possibly be done if the extent of the damage was not excessive.
Thanks for your input!
Marty

[dogridgekraus]

Not for US not to anywhere (at least on Manual Parts I´ve seen"

But why crankshafts and rods with "colour" bearings?

On the F40 that I lately bought on the crankcase and rods have the letter B that stand for BLACK bearings (A is Blue and C is Brown)

So what is the diference!? couldn´t get an answer so far...

Anything else to have in mind for when I'll buy the bearings?

I think Yamaha don´t having undersized / oversized bearings make crankshafts disposable which is "heart" of the motor (IMO) and very expensive...At least here in EU don´t worth get a new crankshaft for a repair

dogridgekraus don´t want to take you the thread.

Almetelo, Your NOT stealing my thread.
I really appreciate yours & everyone contributing to this thread I started.
I seen what your talking about in the parts diagram for the T8 reguarding the color coded bearings.Honda does the same for there automobiles.Its like a blue printed engine so they have to be different sizes.By how many 1000'S IDK...Just within slight tolerances I guess.
A new crank on boats .net was like $380 & a complete powerhead is like close to 4x that! If I have to do anything like that I guess im just screwed & am going to have to scrap that idea. I was hopeing Not,looking "grim" now..
Its a shame they don't make it economical im sure im not the only clown out there in a similar position just wanting to recover from a worthless situation...
Yamahas all about the money I guess!
I should probably at least try doing a teardown at least.IDK...
Thanks:
Marty

[dogridgekraus]

as its not a perfect world any variation from perfect is a variance.
the bearing color selection is based on the actual measured varience.
the F250 has a bearing number on the crank for bearing sizes under or over nominal size.
the block is likewise stamped.
bearing selection can be a chore and plastigaging is mandatory at assy.

its kinda like the F,R and P numbers under the trim tab.
they are a measured variance from a perfect case.

can the crank be welded and reground? most likely.
could the block be shaved and the bearing bores rebored? most likely.
however the machine work would most likely cost more than a new powerhead.

Rodbolt,I stand corrected.Your right the color coated bearing is in the case reguarding the block.
From what ive heard here so far is discourageing...It is what it is I guess..
I know a guy who rebuilds engines mostly race car engines.I talked to him today though & he sounded like he would be willing to help.I have a lot of confidence in him.Not sure about my confidence of the bill to bill to do it though!
Or if you think it would be in my best interest to just buy a used powerhead I found for $425 ? It may be cheaper but it a powerhead I found online.Dont want to buy another piece of junk.I talked to the guy & cant hardly understand his foreign dialect. Its the cheapest ive found though...IDK...
Well,Thanks:
Marty

[rodbolt17]

I would do a complete tear down of what you have and then see what is damaged.
only then can you estimate repairs.
you will find most auto techs simply cannot deal with outboards.
I started out in the late 70's in the auto industry however by age 20 I could machine cyl heads and by age 22 run a crankshaft grinder and by age 26 I programmed and set up CNC lathes and mills .at age 27 I signed up in uncle sams canoe club.
by age 31 was a second class petty officer in the USN(FC2)

don't give up just yet, tear it down, see what,if anything failed, and asses it for repairs.

[almetelo]

don't give up just yet, tear it down, see what,if anything failed, and asses it for repairs.

I think the 1st thing to do is what our master suggested...
Then check if will worth it or not.

If you are in US I belive you can find a cheaper power head for your motor than $425 (but maybe I'm wrong)
And I belive you can get that if you have time to search and you´re not in hurry to fix it.

(lately I bought a cheap seized F40 as winter project or even 1 or 2 years project as I'm not in hurry and want to do it the cheapest way possible but to be good) already have news on this...

Compare parts # on the same year F6 as I'm almost sure they share the same power head so you can widen your search and chance of get a good used power head or cranshaft etc (in case you'll need one)

Here when the outboard have the crankshaft damaged all motor is junk!!!
Here a crankshaft for a F40 cost more than 2000€ +/- $2500 (I just would pay a little more for a running motor) in US that crankshaft costs $700 !!!

Work on car, trucks cranshafts here are common with good results, outboard cranshaft that are repaired frequently fail and they don´t do that type of work.

Good luck on your project

[rodbolt17]

not the first crank that's ever been built up and reground.
however it gets expensive and typically not done on tiny mite stuff.
there are some companies here in the US that specialize in rebuilding cranks that have no bearing under or oversizes.
typically 2 stroke cranks.
but right now you don't know if you need a crank,a crank and a block, a crank block and a rod, a rod or none of the above.

my crystal ball is lost and my magic wand broke.

[dogridgekraus]

I would do a complete tear down of what you have and then see what is damaged.
only then can you estimate repairs.
you will find most auto techs simply cannot deal with outboards.
I started out in the late 70's in the auto industry however by age 20 I could machine cyl heads and by age 22 run a crankshaft grinder and by age 26 I programmed and set up CNC lathes and mills .at age 27 I signed up in uncle sams canoe club.
by age 31 was a second class petty officer in the USN(FC2)

don't give up just yet, tear it down, see what,if anything failed, and asses it for repairs.

I plan on doing a tear down,However I can tell you that I noticed I can get the crank to (visually) move vertically back & forth.That would explain why the flywheel has rub marks on the inside.
So I would guess for now,That the mains definentally have an issue...Ill find out I guess,maybe ill be able to upload some pics for you to observe.
I hope your wrong as me being an auto tech NOT being able to deal with outboards.Though im sure im not as experienced as you or almeteo.
Im not experienced with CNC mills or laths.I do have a friend who is though & can appreciate the degree of skill it takes to do such.
Thanks again Rodbolt!
Marty

[rodbolt17]

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.

[dogridgekraus]

I think the 1st thing to do is what our master suggested...
Then check if will worth it or not.

If you are in US I belive you can find a cheaper power head for your motor than $425 (but maybe I'm wrong)
And I belive you can get that if you have time to search and you´re not in hurry to fix it.

(lately I bought a cheap seized F40 as winter project or even 1 or 2 years project as I'm not in hurry and want to do it the cheapest way possible but to be good) already have news on this...

Compare parts # on the same year F6 as I'm almost sure they share the same power head so you can widen your search and chance of get a good used power head or cranshaft etc (in case you'll need one)

Here when the outboard have the crankshaft damaged all motor is junk!!!
Here a crankshaft for a F40 cost more than 2000€ +/- $2500 (I just would pay a little more for a running motor) in US that crankshaft costs $700 !!!

Work on car, trucks cranshafts here are common with good results, outboard cranshaft that are repaired frequently fail and they don´t do that type of work.

Good luck on your project

I agree,Rodbolt sounds very experienced & I feel privledged to have the opportunity for his advice,
I seen the pic you showed with your project in another thread.I couldn't believe the wear I saw on the cam & the pristine condition the block was in.Musta just bee some type of oil issue in the head or cam,a plugged oil passage maybe.Good thing you have a parts engine with a good camshaft.

The 6-8 hp Yamaha powerheads are hard to find.Let alone used parts.
The one I found was on ebay & that was the cheapest one! I don't know where else to look?? Like you I have to keep the budget low I dont to have more in an outboard than its worth.So the way I see it I have $400 to invest.Maybe unrealistic thinking.
You would think a smaller powerhead would be cheaper in comparison.
Where did you find your block for the F40?
That sucks that you don't think/know a crank shaft for an outboard like mine can be effectively machined/repaired & hold up.I guess the main reason is due to no availability to get different sized bearings rod ETC then?
Even with good machine work done right its still iffy then?
Im gonna keep my fingers crossed.
Good luck with your project.
Thanks Almetelo:
Marty