How to Unclog Speedometer Tube?

[DennisG01]

Although, if that's the extent of the corrosion, it might be worthwhile to build that area back up with thickened epoxy - even close up the hole - as most likely, the interior of the hole is corroded. As long as there's enough meat left everywhere so the internal area (gears) isn't compromised it could work. Clean the aluminum REALLY well - something like phosphoric acid or similar.

[TownsendsFJR1300]

I would think Yamaha, in the machining process, simply drilled that pitot tube hole from both directions, AND THAT's all that WAS DONE..

To introduce the other metal, I don't see them doing that.

My pitot hole, (but I do flush it and it is like new), is VERY HARD to feel /find when I'm going to flush it. There's no way that hole is bigger for a SS piece.

[zenoahphobic]

I would think Yamaha, in the machining process, simply drilled that pitot tube hole from both directions, AND THAT's all that WAS DONE..

To introduce the other metal, I don't see them doing that.

My pitot hole, (but I do flush it and it is like new), is VERY HARD to feel /find when I'm going to flush it. There's no way that hole is bigger for a SS piece.

I've never seen the area of that pitot hole apart, but my experience in cleaning that hole there was what appeared to me always a stainless steel tube in that hole. Maybe modern cheapness they had done away with that extra small tube.

[zenoahphobic]

A picture tells a thousand words. I had another look and didn't realise they were of different engines. The top picture the split pin is where expected, however the bottom leg has very similar corrosion at the same spot, without a split pin, and you are extracting a split pin from far lower down.

Although as stated in my previous post, I've always believed there was a stainless steel tube within there, it appears those stainless steel split pins are not original and were not put there by Yamaha..

Just cleaned my glasses, did I get that wrong, your just holding that pin lower?

[zenoahphobic]

I'm having a bad seeing day!

Is that the oil filler hole on top of the gear case bulb? Never seen that before, what engine is that?

[FabricGATOR]

that thing is in need of replacing.
welding corroded cast aluminum is not going to work

I agree, if I had Trump money, i would replace it...... We'll see what I can do, I have rocket scientist technology and skills.

[99yam40]

I agree, if I had Trump money, i would replace it...... We'll see what I can do, I have rocket scientist technology and skills.

bondo and paint or fiberglass filler and paint may make it look better if that is what you are going for

[FabricGATOR]

The roll pins measures 1/8" x 5/8" and it is also in the other engine's lower unit. I know the history of this vessel since new in 2000 and I am fairly confident this is stock Yamaha SX150TXRY
This was the NON used pitot engine, the LX. The SX is not nearly as deteriorated and the picture I took is really bad lighting. I have no plans of destructive exploration on that engine, but I did see the split and realized it too is merely a roll pin.
No, the inside of the hole where this roll pin was removed is clean as a whistle, so Yamaha has figured out a way to make an alloy that is somewhat compatible with that stainless steel..

The lower units are drained of oil and inverted on my rolling workbench, so these pictures may be better viewed while standing on your head, or flip the monitor.

The pitting will be addressed with the Gougeon brothers technique of wet sanding the metal using mixed epoxy, followed by a 20%-35% cabosil ( to mayonnaise) and finished to working thickness with glass bubbles or qcells depending what I can sweep up off the floor. Prior to epoxy fillers, the corrosion will be arrested with alumaprep etch and then treated with alodine. Additionally, the assembly will get an epoxy coat of zinc chromemate (the good stuff from my private reserve)

I agree, that left one could be considered scrap due to the corrosion but.. really... The lower unit needs to A) hold oil and B) be structurally strong enough to stop the propeller from falling to the seabed. and I am confident that this has those two qualities, at least for the time being.

My advice, do not paint an aluminum boat, an engine, or anything aluminum in a seawater environment with copper based antifouling paint. IMG_1384.JPG

[FabricGATOR]

A picture tells a thousand words. I had another look and didn't realise they were of different engines. The top picture the split pin is where expected, however the bottom leg has very similar corrosion at the same spot, without a split pin, and you are extracting a split pin from far lower down.

Although as stated in my previous post, I've always believed there was a stainless steel tube within there, it appears those stainless steel split pins are not original and were not put there by Yamaha..

Just cleaned my glasses, did I get that wrong, your just holding that pin lower?

Yes, I grabbed that roll pin with my dykes and yanked it out of there. Actually, I levered it out, and it extracted like you would expect a roll pin to extract.
Those first three pictures are all of the same lower unit. The first as found, the second with pin extracted, the third is with a razor blade for size reference, lying atop the underside of the anti cavitation plate. The lower unit is inverted.

[DennisG01]

OK, so if that's truly meant to be there by design... what do you think the purpose is? I've cleaned so many pitots on so many engines over the years and have just never remembered seeing that. But, again, it's not like I'm peering into the hole. And, maybe under normal conditions (no corrosion), the roll pin wouldn't be viewable, anyways? But it still begs the question of 'why'? Is it placed there to aid in casting?

Still seems awfully coincidental that the corrosion is centered in that area, though?

[FabricGATOR]

OK, so if that's truly meant to be there by design... what do you think the purpose is? I've cleaned so many pitots on so many engines over the years and have just never remembered seeing that. But, again, it's not like I'm peering into the hole. And, maybe under normal conditions (no corrosion), the roll pin wouldn't be viewable, anyways? But it still begs the question of 'why'? Is it placed there to aid in casting?

Still seems awfully coincidental that the corrosion is centered in that area, though?

I believe that with the engine tilted, at the dock that is the way the vessel sat unused, that pitot area was close to the waterline. I also suspect that there was a transient current electrolysis condition and that may have been the path of least resistance.

How could I check to see if I still have an electrolysis condition when afloat? How would I set up and perform a test?

I'll have to ask my brother. He has a set up on his sailboat that he regulates the vessel grounding to the anodes with a potentiometer and a gauge. It has been a few years since he explained. I remember him explaining how you can actually create an electrolysis problem by having too much sacrificial anode exposure.... something to that extent.

[holmen78]

Take a look at this page:
https://www.boatzincs.com/corrosion-...electrode.html

Do the 3 quizzes and read the explanations.

You need a AgCl probe and a multimeter to measure your boats potential in water with battery switch on and off. The measurement should stay between -950 to -1100 mV. If not there is something wrong with your wiring or something else is leaking current nearby, or insufficient/wrong material sacrificial anodes.

[TownsendsFJR1300]

Take a look at this page:
https://www.boatzincs.com/corrosion-...electrode.html

Do the 3 quizzes and read the explanations.

You need a AgCl probe and a multimeter to measure your boats potential in water with battery switch on and off. The measurement should stay between -950 to -1100 mV. If not there is something wrong with your wiring or something else is leaking current nearby, or insufficient/wrong material sacrificial anodes.

Oops..

Meant to push the "like " button...

[DennisG01]

I believe that with the engine tilted, at the dock that is the way the vessel sat unused, that pitot area was close to the waterline. I also suspect that there was a transient current electrolysis condition and that may have been the path of least resistance.

Except... the last part to leave the water as you tilt up is the very front of the gear housing. The pitot is higher than the front edge (nose) of the gear housing - meaning, the pitot area wouldn't be in the water by itself. The gear housing should show the same pitting, which it doesn't seem to. It really does look like a sort-of half-circle, centered around the pitot hole. Very strange.

Yes, some anode compositions can overprotect and cause excessive paint lifting, leading then to corrosion. But it wouldn't cause the pattern you have there. But, here's some good reading material on the subject. These guys, by the way, make a VERY good anode: https://performancemetals.com/

Another thing you can easily check is the bonding system - making sure all metal parts are electrically bonded either via direct contact with each other or the use of small diamter, SS braided wire.