Replacing an outboard any help appreciated!

[Smagu]

Hello.

Replacing an outboard from a ~1992 yamaha 60 to an older Yamaha 80.

The Yamaha 80 is in good condition with 110 psi over all cylinders and runs sweet. The 60 coming off the rib, has 75 psi top cylinder other two 90.

Mounting brackets are identical which is handy.

Can I use my old 703 controls. Yamaha 80 has 703 controls also. Do cables come in different lengths? (The controls on the Yamaha 80 are so much smoother than the ones I have on)

The big question is a large section of the skeg is missing on the yam 80. The prop shaft appears to have a slight bend in it. Seems to be around 1-3mm enough that you can see it’s not turning straight on close examination.

The two lower ends looks identical can I just put the yam 60 leg onto the yam 80 leg? Annoyingly the yam 80 goes in and out of gear very smoothly where the yam 60 makes some grinding.

In summary
1. Any tips for replacing outboards?
2. Should I replace the legs or put a skeg extender on and see how it is? (Would this do any damage to the power head?)
3. Should I replace controls or just disconnect the wires controls and plug them onto the yamaha 80 going on.

I’ve attached the serial numbers for both engines

[HDAV]

Personally if you have a hard flat surface concrete ideally I would make a stand from timber heavy 4” borrow an engine crane and swap them over.

However beforehand I would remove the lower units and check both over for any additional nasties (compare part numbers in advance) might be easier to do the swap with the lower units off the motor and I would
Probably swap the control boxes

Hopefully the same lower units are used, and a swap is easy, get the prop sent off for a refurb while faffing about with engines …….

[Tommy c]

https://www.marineengine.com/
This is the site I use for part number cross reference.
It may or may not be of use ��

[beamishken]

Gear cases are the same, afaik almost everything else is different. Shaft has different splines into crankshaft so its a full stripdown to use the case.
I ran a similar year 85 to the one you have with a bent propshaft for years & it never suffered because of it, for your purpose I'd just run it. If the missing skeg is an issue get it welded, shouldnt be expensive for the right welder.
Whats your plan for the old engine?

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[Smagu]

So will swap engine and controls as above. Remove lower leg on 80 check it over and replace impeller.

Any sense in trying to bend the prop a little with a jack or a long pipe?

Not sure what to do with the old engine. Either sell it as is for spares or repairs it still starts and runs and sell boat/ give it away. Or put it on the old speed boat and sell both together.

[Matt]

I know we have all different "nope" thresholds, but I wouldn't run a gearbox that has a 3mm bend in the end of the propshaft.

[Smagu]

Honestly I’m just guessing. Buying the measuring tool at the moment will report back when I get the actual amount it’s out

[beamishken]

Originally Posted by Matt

I know we have all different "nope" thresholds, but I wouldn't run a gearbox that has a 3mm bend in the end of the propshaft.

Mine was about 6mm out ran it regularly 5 years without issue wont even notice 3mm deflection

Originally Posted by Smagu

Honestly I’m just guessing. Buying the measuring tool at the moment will report back when I get the actual amount it’s out

I've seen them straightened with a DTI & vee blocks in a press with the shaft out of the box, not sure how it would go with it assembled. Maybe a tube over the shaft bending up towards the av plate rather than away so you putting the pressure upwards not down on the case. But I'd honestly leave it be. I've got a 60 with a siezed power head so maybe interested in your old engine for spares but in all honesty if you chuck it back on the old speedboat & it runs you'll probably get most if not all your money back selling as a project

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[Matt]

Yeah, I hear you and it'll likely be fine - it's even what I might have put up with when I was younger. But it's not what I'd choose to do as the mid 40's grumpy old fart that I am now. I'd be sorting it all out, I am very risk averse to anything that can lead to mechanical failures....they always happen at the most inconvenient time!

[beamishken]

Originally Posted by Matt

Yeah, I hear you and it'll likely be fine - it's even what I might have put up with when I was younger. But it's not what I'd choose to do as the mid 40's grumpy old fart that I am now. I'd be sorting it all out, I am very risk averse to anything that can lead to mechanical failures....they always happen at the most inconvenient time!

The guys emigrating next year doesnt need to spend winter messing with it when he can spend it playing with it

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[whiskylee]

Check the gear oil & seals
Good video attached

https://youtu.be/z9S14wI79nc

[Matt]

I think he exactly is going to be spending winter missing with it - hence the GF's annoyance.

Anyway, give it a go. I've certainly run many "suboptimal" engines over the years.

Originally Posted by beamishken

The guys emigrating next year doesnt need to spend winter messing with it when he can spend it playing with it

[Smagu]

So update. I decided to go with the super sketch jack idea…. Surprisingly I think it worked.

Initially I had 4.2mm of difference along the entirety of the shaft. After around 2 hours I got that down to 0.56mm at where the splines and the screw thread begins on the prop shaft.

Seems to have went in steps 4.2mm to 2.5mm then 0.56mm. I’ve stopped now. The forces involved were surprisingly high. So don’t want to push my luck and try it any more.

I had some gear oil leaking out when the pressure was applied but once jack was off this stopped. Going to replace oil seals as I suspect I bent the metal within them.

No added play in the prop shaft or cracks on the casing. Wouldn’t like to do this with a new engine. Heart in my mouth for 2 hours

[Smagu]

Those eagled eyed amongst you may have noticed the missing skeg. Thinking of putting one of those gator gards on?

[Smagu]

So I know I said I wouldn’t… but I did. Got it down to 0.13mm (0.0055 thousands of an inch) where the splines stop and the screw thread begins. Now I’m definitely stopping.

[beerbelly]

Originally Posted by Smagu

So update. I decided to go with the super sketch jack idea…. Surprisingly I think it worked.

Initially I had 4.2mm of difference along the entirety of the shaft. After around 2 hours I got that down to 0.56mm at where the splines and the screw thread begins on the prop shaft.

Seems to have went in steps 4.2mm to 2.5mm then 0.56mm. I’ve stopped now. The forces involved were surprisingly high. So don’t want to push my luck and try it any more.

I had some gear oil leaking out when the pressure was applied but once jack was off this stopped. Going to replace oil seals as I suspect I bent the metal within them.

No added play in the prop shaft or cracks on the casing. Wouldn’t like to do this with a new engine. Heart in my mouth for 2 hours

looking at that has made me feel squeamish

[Matt]

Originally Posted by Smagu

Those eagled eyed amongst you may have noticed the missing skeg. Thinking of putting one of those gator gards on?

There's not really enough skeg left by the looks of it, certainly for a skeggard that I've used before.

[Smagu]

Originally Posted by beerbelly

looking at that has made me feel squeamish

It was extremely unpleasant to do… It’s a lot of pressure on the cavitation plate enough to split 2inch thick bit of timber.

[Matt]

I'm surprised you've got away with it - but if you have, bravo.
If you're going to replace the propshaft seals - perfect time to weld a new skeg on.

Make sure they're a good welder, skegs do take quite a bit of load.

[Limecc]

Originally Posted by Matt

skegs do take quite a bit of load.

Only when they strike something. Otherwise very hydrodynamic hence not much load. On an ordinary use outboard manufacturers don't need to (and don't) build much lateral strength into them.

Obviously not too critical when people can use them without one. Must lose some rudder function at displacement.

Have we discussed this before?