how old is this damage to outboard (roughly)

[phantom 19]

It is 100% corrosion. It is a really bad design, the mount is encapsulated by that stainless plate and rot sets in and expands and blows the whole lot apart - I can take photos of at least five scrap engines with exactly the same problem. Even ones that we fitted new replacement legs to in the mid 90's were doing it again exactly the same. It was never as bad with the manual start version, which I always put down to lack of battery current to mess things up.

Anyway I would be looking for 120psi plus ideally.

[ShinyShoe]

120 on a hot engine?

I'm guessing these may have been cold?

[Nightfisher]

Perhaps if as you say it's a common problem, the nut is overtightened at factory which either hair-line cracks the case, creating a CASE corrosion problem. Galvanic corrosion happens when two dissimilar metals meet with or without water, with exception of stainless steel. It's often used to connect weaker metals, especially Alloy or Aluminum specifically to avoid galvanic corrosion. Overtorque however could cause a problem especially with the addition of heat which as we know expands the joint even tighter. All kinds of stuff about why SS is used to fasten such metals sealing with anti-corrision. I've used stainless steel fasteners and screws on any metal parts, boat, car or other and never a corrosion problem.

[beerbelly]

that's strange as an ex biker we often replaced our engine casing bolts with stainless for a, bling and b, the oe crosshead screws were made of cheese and often the head chewed up . but after a while the stainless allen bolts would corrode with the alloy engine and seize the fix was to coat the stainless fasteners with coppaslip grease never had a problem undoing a coppaslip coated stainless fastener

[willk]

Originally Posted by Nightfisher

Perhaps if as you say it's a common problem, the nut is overtightened at factory which either hair-line cracks the case, creating a CASE corrosion problem. Galvanic corrosion happens when two dissimilar metals meet with or without water, with exception of stainless steel. It's often used to connect weaker metals, especially Alloy or Aluminum specifically to avoid galvanic corrosion. Overtorque however could cause a problem especially with the addition of heat which as we know expands the joint even tighter. All kinds of stuff about why SS is used to fasten such metals sealing with anti-corrision. I've used stainless steel fasteners and screws on any metal parts, boat, car or other and never a corrosion problem.

Aluminium/alloy and Stainless Steel are not happy bedfellows when an electrolyte is present: Galvanic Corrosion – keep those metals apart! | Anzor Australia's blog - provides technical tips, case studies, and other useful information about stainless steel fasteners

[Nightfisher]

Austentic Stainless
(Type 302/304

[miktek]

Originally Posted by ShinyShoe

120 on a hot engine?

I'm guessing these may have been cold?

Yes, that was readings when cold.

[Nos4r2]

Worth checking your compression tester is showing the right figures. 5% difference between cylinders is ok. 100psi really isn't good, but it could easily be down to a poorly calibrated tester.

[ShinyShoe]

Originally Posted by Nos4r2

Worth checking your compression tester is showing the right figures. 5% difference between cylinders is ok. 100psi really isn't good, but it could easily be down to a poorly calibrated tester.

But also normal to test with the engine warm if I am not mistaken?

[miktek]

Hi guys, update time.

Got myself a near mint mid section and because it comes with a far better condition steering arm (not too happy with one that is on it now, very corroded, a problem with these engines) I'm going to take the powerhead off and rebuild. Have talked it though with a very competent outboard fixer and he will help me if needed, but says it's mostly just bolt off then on again.



This obviously means more work than before and includes undoing the 4 bolts that go DOWN from the powerhead as well as the 8 that go UP into it. All of the 8 bolts come away freely, but 2 out of the 4 (the 2 at the back of outboard) are a pig to get to. Any tips? see pic. This one is not too bad and should come away with a bit of heat treatment, but the other one is buried, looks like I'll have to take a few bits off the powerhead to get in.



Referring back to my first picture, I'll be needing 2 new gaskets for either side of the small section that connects the powerhead to the mid section (the bit that gets covered by the wee plastic apron). I assume that a local yamaha dealer will have such gaskets even if it is a 25 year old 1990 outboard?

Thanks for all the help again

[HughN]

Originally Posted by miktek

I assume that a local yamaha dealer will have such gaskets even if it is a 25 year old 1990 outboard?

If they aren't interested in assisting with the spares, eBay doesn't help and all else fails, try putting the part number in at:www.ajsutton.co.uk. Its a bike place but their computer doesn't seem to know that and shows what is available in the UK and/or Japan whether it is a bike or an o/b. I've got spares for a 25 yr old Yam from there when other sources have been unable to help.

[Xk59D]

why not just get bits from Davie?

[miktek]

Originally Posted by HughN

If they aren't interested in assisting with the spares, eBay doesn't help and all else fails, try putting the part number in at:www.ajsutton.co.uk. Its a bike place but their computer doesn't seem to know that and shows what is available in the UK and/or Japan whether it is a bike or an o/b. I've got spares for a 25 yr old Yam from there when other sources have been unable to help.

thanks

Originally Posted by Xk59D

why not just get bits from Davie?

Just the distance being the reason to be honest mate

[Xk59D]

as Davie helped you already i would just go back there and get him to ship you the bits.

failing that, yampower is in glasgow too.

[SPR]

Originally Posted by Xk59D

as Davie helped you already i would just go back there and get him to ship you the bits.

failing that, yampower is in glasgow too.

+1 Davie all the way


www.firstaidatsea.co.uk
www.SPRmarine.co.uk

[jambo]

Originally Posted by SPR

+1 Davie all the way


www.firstaidatsea.co.uk
www.SPRmarine.co.uk

Yep me too.


Sent from my iPhone using RIB Net

[phantom 19]

The four bolts that you refer to going down from the tray are the tray mount bolts. Normal procedure is to remove the powerhead first then when it is clear undo the tray mounting bolts and remove the tray. As you have a replacement mid section you can just snap off the bolts if worst comes to worst.

[camelgas]

Seems a bit off not to use davie for bits after he helped you !.

[miktek]

Originally Posted by camelgas

Seems a bit off not to use davie for bits after he helped you !.

I've gone from thinking about trying to fix it, to not even attempting it and splitting the engine, plus I'm still in the midst of completing a partial refund from the seller. Now I'm back to fixing it. I thanked Davie for taking the time to speak to me when I popped up last week, I could see how busy he was. I don't like to viewed as wasting peoples time and if it comes across like that I apologise.

I managed to split the head from the mid section today, 25 years of friction/heat made it almost fuse together. Put the new mid section on the transom arms and connected the power trim and all worked great. Got the powerhead on tonight and it's all lining up ok. Few more hours to go on it over the weekend.


greenshot

[lightning]

It looks like you made a deal with the seller, and the engine is on the way to being good again, so it seems like it will end well.