So I just bought a Mac X....

[Inquisitor]

My big concern is that it might be heavily corroded inside the cooling channels, with no way of repairing that.

I know very little about OB repair. Haven't needed to so far. Maybe someone will weigh-in. In the old days, I vaguely recall there was a flush for radiators that would remove scale and stuff. A little tougher since its not recirculated in an OB, but as industrious as you are, I'd bet that be a minor speed bump for you.

[dlandersson]

I looked around for a class in outboard engines a few years back. I was surprised and disappointed with the lack of offerings.

My big concern is that it might be heavily corroded inside the cooling channels, with no way of repairing that.

I know very little about OB repair. Haven't needed to so far. Maybe someone will weigh-in. In the old days, I vaguely recall there was a flush for radiators that would remove scale and stuff. A little tougher since its not recirculated in an OB, but as industrious as you are, I'd bet that be a minor speed bump for you.

[opie]

Drifter,
I was about to suggest taking out the thermostat and setting it in a pot of water and testing it. It is just two small bolts once you remove protective shroud.
Look inside and clean what you can. Make your own gasket with anything suitable or gasket compound. I have never bought a factory gasket, even the manifold gaskets I make.
For that matter, while the cover is off, try removing the right and left manifolds. There is the occasional break of a bolt head if they are seized so soak with oil for a couple of days. If one breaks off you will have to drill it out and retap it. A pain but I've done it. Look at anodes also while in there.

[Drifter]

I've ordered a liter of hydrochloric acid...

Will try soon to get the thermostat out (maybe not this weekend, as the Admiral has booked me for family stuff). One thing I'd like to try is to add a lot of items into the plastic water tub, so there's less water, and then add the acid to the water.

I strongly suspect I'll get an email soon saying my order is cancelled because they won't ship a bottle of acid here but I'm giving it a go

I found a video where a guy tested the acid, some vinegar and "Saltaway", a specialist product that would cost a fortune to ship. The acid seemed to work best, and didn't damage an impeller he tried, or a gasket.

Regarding gaskets, I bought some gasket paper, so while the thermostat I ordered comes with a gasket I can also potentially make my own.

Even if the thermostat solves the issue I think a dilute acid bath in the cooling channels could help reduce the corrosion build up. After all, this boat and engine have spent 25 years in the sea, so I doubt it has ever been treated to a fresh water flush - which is why I'm feeling a sense of doom...

On a brighter note I'm starting to think it's possible to get to all of the channels, if willing to split the engine apart completely. Obviously I really don't want to do that but if its possible then that's a lot better than having to declare the engine ruined and scrapping it.

I have a lot of respect for both the boat and the engine, for a trailer-sailer to have survived so long, in such good condition without ever getting a rest from the sea and salt is remarkable.

Just that right now I really want a boat, not another project...

[Drifter]

BTW, regarding anodes I already replaced the trim tab but I imagine there's a 2nd one somewhere? I'll take a look.

Opie, why remove the manifolds?

[opie]

removing manifolds exposes two anodes, one in each side (lots of help in doing this in this forum history). Almost all water passsges will be exposed. No need to split engine. (In fact, crumbly anodes may be contributing to possible blockage.)

[Russ]

BTW, regarding anodes I already replaced the trim tab but I imagine there's a 2nd one somewhere? I'll take a look.

Opie, why remove the manifolds?

On my Suzuki, the trim tab also combats sideways blade pressure. It's installed at a slight angle to direct prop wash sideways a bit to compensate for sideways blade pressure. Does yours have similar?

If it were me, I wouldn't remove manifolds. Mostly because my luck would snap a bolt and cause another headache.
My money is on bad thermostat. And I've "tested" them in a pot of hot water and they opened but failed in the car. So that is not a definitive test in my opinion.

My money is on bad thermostat.

[opie]

perhaps calling them "water jacket covers" would make the job less scary. To some, manifold may conjure up intake or exhaust, and these covers are just water passage covers.
If motor is old and these have never been removed they need to come off sometime in near future, but I must agree that checking tstat is more possibly gratifying and first to do.

[Drifter]

It's installed at a slight angle to direct prop wash sideways a bit to compensate for sideways blade pressure. Does yours have similar?

Yes, I believe that's why they call it a trim tab, so you can adjust it if the boat is turning from that. The original was fitted straight, so I replaced it the same. Can't say that it is or isn't causing any sideways steering, as there's so much slop in the steering that under motor power it looks like I'm tacking down the river anyway

Almost all water passsges will be exposed. No need to split engine.

That's great to know! Does sound like something that needs a few repeated squirts of WD40 on the bolts for a few days beforehand.

One thing that's frustrating me is we are coming up for the 'Ramadan' month of fasting soon. Means Muslims cannot eat or drink during daylight hours, for all of April I think it is this year. Generally not the done thing to go swanning around in one's yacht, swigging cold drinks and having fun while others are suffering, so was really hoping to get a few weekends out of the old girl. Instead seems I'll get parts arrive, hopefully get it fixed, just in time to say...

"Welp, guess we'll wait a month it see if it works."



And yep, just got the email saying that my order for a bottle of acid has been cancelled.

To some, manifold may conjure up intake or exhaust

Absolutely, that's exactly what I thought you meant

[Be Free]

If you decide to take off the side cover you will be able to access more of the cooling passages. Because of the high probability of at least one seized bolt I'd save the side cover for last. Try to loosen all of the bolts before you commit to it. If they are not seized it is a pretty easy job so go ahead and do it.

Be patient if the bolts do not come out easily. WD40 or any penetrating oil will have minimal to no effect until you get the bolt backed out a little. Gently tapping the bolt head to break up corrosion in the threads will help more than oil at first. Those small bolts will break off if you rush the process. Time is your friend. If you think a seized bolt is hard to take out wait until you try without the head.

You will need to remove the tilt switch and possibly a wire holder to get to the bottom bolts on the port side. Don't take out more than absolutely necessary. It can be frustrating getting the bolts back into the confined space at the bottom. If I remember correctly there is not a gasket on the cover. It is sealed with an o-ring embedded in the cover. There is definitely an anode inside. I don't remember ever taking one off on the starboard side so I can't help there.

The water passages are pretty big but they are twisty. Run a small wire or weed trimmer cable as far as you can. I've also used large zip ties to poke them out. Blow the passages out with high pressure air or water with the thermostat in place. That way anything you loosen on the port side can't get back to the water pump. It should just end up in the foot and should blow out when you start the engine.

I wonder what a pressure washer would do with them? Has anyone tried cleaning out the passages that way?

[Tomfoolery]

My post two thirds of the way down page 14 of this thread has the service manual page showing that cover, o-ring, and the internal anode, plus bolt and torque specs for reassembly. I don't know if there's a cover on the other side, and the book doesn't show one.

[Russ]

I still have money on a bad thermostat.

However, you might still want to flush that motor anyway. Apparently, some folks connect a tub under the motor fitted with a pond pump connected to the water intake of the motor and run it for several hours. Recirculating a solution to flush the grime out of the heads.

Solutions of this stuff might pass your shipping police.

[opie]

Drifter,
This may help re: anodes. This refreshes my memory. The starboard side means taking off the intake manifold with carbs attached.
1st time: two days
2nd time: 8 hours
last time: 3 hours.
(I have some tips for this procedure as do others here I guess.)
https://macgregorsailors.com/forum/view ... de#p342529

[opie]

Drifter,
More stuff to read to show how alarms are wired and how "flameout" occurs.
(ignore my handwriting)

[Drifter]

I'm literally overwhelmed by the helpful and encouraging responses

Thank you