How to patch holes in lower unit?

[DownYonder]

We inherited a 1987 70hp Tohatsu with less than 200 hrs that I am running on a Key West 1720. It runs great but it was left in fresh water for about 5 years when my FIL became ill and electrolysis pitted the lower unit. There are 3 holes each about the size of a dime. I need suggestions on the best product to use to patch the holes. I'm hoping to find something to coat the entire lower unit and fair it.

 

[ahicks]

I would suggest you take it to a boat or engine repair facility for welding. Safe bet it will not be the first one they've seen, and they'll have the experience to handle it professionally. I would NOT try to use some type of glue or epoxy, not for the repair anyway.

 

[gm280]

If we had some pictures we could offer more exacting ideas. Obviously we don't know where such holes are and therefore can't offer anything but typical ideas. You could use some JB weld to cover over them. You could also have them welded up, but that is about it with me without seeing them. JMHO

Oh and I almost forgot, welcome aboard to iboats! Nice to have a new member! :thumb:

 

[DownYonder]

here is a picture of one side...the other side has 2 smaller holes in about the same area

 

[GA_Boater]

here is a picture of one side...the other side has 2 smaller holes in about the same area

That's an awfully big dime!

How does the midsection look? It's probably as bad if part of it was in the water.

What about corrosion inside? I would tap all over with a hammer. You will have the time while looking for a new lower unit.

 

[DownYonder]

That's an awfully big dime!

How does the midsection look? It's probably as bad if part of it was in the water.

What about corrosion inside? I would tap all over with a hammer. You will have the time while looking for a new lower unit.

Corrosion extends about 6 inches above the cavitation plate but not as bad. The remainer of the motor is fine. From what I can tell, the internal portion is not pitted. I tried to find a lower unit but have not found a used one and my local dealer said that there are no new ones remaining.

I was hoping that you guys would say that fiber glassing (or similar) the lower unit would work. That way I could fair the FG with minimal addition drag.

 

[GA_Boater]

Look for a parts motor. One with a blown powerhead and a complete lower unit.

 

[Scott Danforth]

I would be checking ebay and craigslist for a used lower. there is a 2006 lower on ebay right now.

 

[racerone]

Classic , junk aluminum used in some outboards.-----Have seen the same damage on Yamaha motors too. Once that corrosion starts it is difficult to stop it.

 

[pvanv]

Assuming your model is M70A2. Year is irrelevant. You need a donor motor, maybe one with a blown power head, to get the casting you need.

 

[DownYonder]

Assuming your model is M70A2. Year is irrelevant. You need a donor motor, maybe one with a blown power head, to get the casting you need.

For some reason I was thinking it is a 70B but after looking at tohatsu parts list, it may be a A2. I'm 10hrs away from it for the holidays and will need to check the serial number again.

In any case, you are correct about a donor motor. Are there any web sites to search for such animals.....like used car parts?

 

[TOHATSU GURU]

Compatible lower units would be the 50C, 55B, 60A and 70A. Keep in mind that no parts are available for this engine(except for impellers and cdi units) so it would be in your best interest to graveyard it.

 

[w2much]

I agree with all of the above. Even with a welding patch job done there may still be an integrity of strength issue. That being said , if you can remove it,which may be another whole issue, do so. The hole I see is in the exhaust cavity. If it is above the oil seals you may try to weld it, grind down some of the corrosion and epoxy the outside. See UTube Dangar Marine has a good video on this. So if this can work for you and motor runs you may try it out. Bring oars cause I am not so certain that there could be much life left in that lower unit.

 

[DownYonder]

Hold everything!!! The motor is a M 70 B serial #20416. Contacted a shop this morning that said they can still get parts, so now I have to decide if spending the $$$ on a lower unit is worth it. The motor only has around 200hrs on it and runs good. Decisions...Decisions!

 

[gm280]

I would see how it looks removed and clean up to make a determination. Of course a new lower section will be pricey, but if a competent welding shop can't do a great job, you may not have an option. But I would remove and clean and see... JMHO

 

[pvanv]

The gearcase is NLA new. That said, the Long shaft LU complete is out of stock, but when/if available, costs over $2300. Same deal with the UL LU, but it would cost about $1800 if you could find one new. You either need to locate NOS (new old stock), aftermarket, or used. If it's just corroded in the exhaust housing, an epoxy job might get you by.

 

[DownYonder]

The gearcase is NLA new. That said, the Long shaft LU complete is out of stock, but when/if available, costs over $2300. Same deal with the UL LU, but it would cost about $1800 if you could find one new. You either need to locate NOS (new old stock), aftermarket, or used. If it's just corroded in the exhaust housing, an epoxy job might get you by.

The corrosion appears to be limited to the shell. I'm selling the boat and think that finding a used lower unit will add more value to the boat/motor package than the cost. I have found two potential used LUs. Repairing it will probably be too much of a negative when trying to sell.

thanks

 

[TOHATSU GURU]

Most parts are still available for the three cylinder 70 B