Yamaha 200 powerhead rebuild

[Tobb1]

I am in the process of rebuilding my 200 Yamaha V6 not sure what year. It needs two new piston and one cylinder needs boring. Maybe both.

Picture og the least damaged cylinder
427229427230

Pictures of the most damaged cylinder
427231
427232
427233

[Tobb1]

When I am finished taking everything apart i will bring the Block to a machinist and have everything measured. Maybe i am lucky and ut can just be honed. There are no deep scratches.

Also looking for pointers on any simple mods for increasing performance now that i have everything apart.

[Merc 2.5]

Just make sure it's a reputable outboard machinist,, prob gonna need 2 sleeves and all bored imo

[Tobb1]

Why would it need resleeving if it is going to be bores?

All the other cylinder look very nice. No scratches and still visible cross hatching.

[Tobb1]

Btw, this is my first outboard rebuild so there will probably be som questions on the way.

[Merc 2.5]

There is actually a list of reasons why it would need sleeves, mine was not near as bad and didnt measure to bad but still got a sleeve, it's the correct way, James Perry explained reasons for sleeve to me but I cant word it like he does , there will b others to chime in with me , lots of guys would do 6 sleeves , but u prob dnt need 6 .. also chris Carson could help u out. But main thing u can do is make sure u r using one of the best mach guy as possible, if the block isnt perfect then the rebuild will never last

[Merc 2.5]

And if machinist does say needs sleeve then the heating process for sleeve can distort other cylinders, which is y bore those to, I got 1 new sleeve and all 6 bored and o ly had 1 lightly scuffed cyl

[Markus]

Is it a vertical or horizontal reed 200?

[Tobb1]

It has the vertical reeds.

I got a little more work done today, i am ready to take the pistons out. I just need to get the correct tool for the connecting rod bolts tomorrow.

It seemed the crank bearings were worn out, there was a bit of play in the bearings.

Will check more tomorrow when i have the crank off.

[Tobb1]

I am trying to find a guide and some specifications for measuring the play in the bearings, but can not find any. How much play is ok? The lower Main bearing has some radial play.

[Merc 2.5]

U will need to put all new bearings in the build. I wouldn't worry to much about the slack as long as crank is gud , needles been known to scuff up a crank

[Tobb1]

I understand that to make the engine as new I need to replace all bearings, pistons, sleeves etc. But that is not the goal here. I want to use as much as I can and replace the parts that has to be replaced. So if some of the bearings can be reused, they will most likely be reused.

[FORBESAUTO]

On average max radial clearance on the roller type bearing the size of a main will be .010, personally I would cull it over .005. A new one is near 0 installed (The press fit tightens it up from expanding inner race) You dont want any movin goin on on your crank. Probably won’t find s spec on that under your motor, you can go to a bearing manufacturer web page and look at a chart with dimensions of bearing and see specs.

[FORBESAUTO]

Can’t say I’ve actually measured one, the main thing I check is for smoothness and if if I can feel much radial play, it’s gone. (So I’m guessing my cull meter is around .005):D

[Markus]

It has the vertical reeds.


Then the two meaningful bolt-ons are:
1. Higher compression heads, to make more power from what you stuff in
2. Horizontal front-half (and what goes in front), to stuff in more

[Tobb1]

What is a safe compression to run on our european 95 gas?

Is the carbs also different on the horizontal reed engines? Can i use the carbs i have if change the intake and reeds?

How much increase in power can i expect from these mods?


Then the two meaningful bolt-ons are:
1. Higher compression heads, to make more power from what you stuff in
2. Horizontal front-half (and what goes in front), to stuff in more

[Markus]

What is a safe compression to run on our european 95 gas?

Is the carbs also different on the horizontal reed engines? Can i use the carbs i have if change the intake and reeds?

How much increase in power can i expect from these mods?

Carbs are bigger on the horizontal reed engines. I think the (horizontal) 225 was 34 mm, while the (vertical) 200 was 32 mm, looking at late eighties engines. I am a continent and an ocean away from my Yamaha V6 service manual, though.

How much power you lose from the smaller carbs, I don’t know, but there was a reason why Yamaha put bigger carbs on the 225.

Something like 145 psi of compression with RON 95 (Europe), which is equal to (RON+MON)/2 90 (US).

Power wise, you would end up somewhere between the actual output of the 200, which was probably around 200, and the actual output of the 225, which was probably around 240. (I remember the 225 fuel consumption per specification reflecting more than a 25 hp increase)

[Euroski]

The bigger question is, what cause the failure? Any ideas?

[Tobb1]

Thanks! I can check the bore on mye carbs tomorrow and check if they are 32 mm.

But for this season i think i just want to get everything up and running. I have a lot of work to do on the boat as well.

Thanks for your reply!

Btw, do you have an exhaust adapter plate for sale?

Carbs are bigger on the horizontal reed engines. I think the (horizontal) 225 was 34 mm, while the (vertical) 200 was 32 mm, looking at late eighties engines. I am a continent and an ocean away from my Yamaha V6 service manual, though.

How much power you lose from the smaller carbs, I don’t know, but there was a reason why Yamaha put bigger carbs on the 225.

Something like 145 psi of compression with RON 95 (Europe), which is equal to (RON+MON)/2 90 (US).

Power wise, you would end up somewhere between the actual output of the 200, which was probably around 200, and the actual output of the 225, which was probably around 240. (I remember the 225 fuel consumption per specification reflecting more than a 25 hp increase)

[Tobb1]

I bought it like this, so I am not sure. Probably a lean condition, lack of oil or water. I am cleaning and rebuilding the carbs, mix oil directly in the gas, and change impeller in the water pump. So hopefully it will not happen again��



The bigger question is, what cause the failure? Any ideas?

[Markus]

Btw, do you have an exhaust adapter plate for sale?

I think I have one that has been enlarged for better flow, as well as a cut exhaust pipe to Wayne Taylor’s specs.

[Jamie Nichols]

Was that thing ingesting crank bearing metal?

[Tobb1]

So far the bearings look like they are in one piece. I checked the main bearings more thoroughly now the lower needs replacing. There is a slight radial play, and it doesnt roll smooth all the way around.

Top bearing seems fine.

Center ones is difficult, i am thinking to take the lower and top bearing off and torquing the crank down with ONLY the center bearings and feel for play and checking if it rotates smoothly.



All journals look fine except the one om the cylinder with the most damage.
There is some marks om the crank journal on the most damaged cylinder. Not deep scoring, but definately noticable when running my nail over.

427415427416

[Merc 2.5]

Yep that crank is a lamp post now, if you try to use it it wont last long at all, outboard cranks really cant b repaired, gonna need find a crank,

[nitro_rat]

Yep that crank is a lamp post now, if you try to use it it wont last long at all, outboard cranks really cant b repaired, gonna need find a crank,

:iagree:

Merc 2.5 is right, that crank is trashed. Find another. A wanted ad in the classifieds here will probably turn one up.

[Tobb1]

Looks like i have already found a new crank, maybe even a NOS crank. Will know more tomorrow.

[Jamie Nichols]

I didn't know those cranks were non serviceable?

[Markus]

I didn't know those cranks were non serviceable?

Dave Eden can fix them.

The official Yamaha rebuilt powerheads from HydroTec used his cranks.

[Tobb1]

Small update, the machinist checked the crank and it is ok. The damaged journal measured 0,01 mm different from the others so ut was within spec. One cylinder had to be bored 0.50 mm oversize. All others was within spec. Hopefully i will be picking it up this week.

Any recommodations for ordering parts?

[Merc 2.5]

Does the crank still have a scar on it?

[Tobb1]

Crank is polished and scar is almost gone, have not den ut for myself yet. Will pick up this week.

[DoktorC]

Crank is polished and scar is almost gone, have not den ut for myself yet. Will pick up this week.


You're going to want to make sure that mark is totally gone or the roller bearing with tear that journal up in no time.

The cylinders on the other hand will clean up with a hone or boring first over. There's lots on material to work with on these motors so not to worry there.