So I just bought a Mac X....

[dlandersson]

Lets see how ya feel after you get the bill...

I'm literally overwhelmed by the helpful and encouraging responses

Thank you

[Drifter]

So....

Yesterday the thermostat and gasket arrived...

Wasn't looking forward to it but tried taking the engine apart, you know, open heart surgery stuff. Scary.

Actually didn't seem so bad. None of the bolts were on tight. I added anti-seize to the threads, put them to one side, eased off the thermostat cover. As expected, quite corroded and nasty-looking, but no really terrible or obviously blocked.

Got my extra-powerful vacuum cleaner and tried sucking that sucker. Why not?

Tried putting the old thermostat in some hot water. It opened OK. Then tried using my fancy kettle's ability to choose the temperature (I'm a coffee snob) and set it at 70C, put both the old and new in a glass of water... They both failed to open. Ha. They're supposed to open at 60C.

Anyway...

Spent some time scraping off the old gasket, remembered to draw the outline of the new one onto some gasket paper so I can make a spare or two - and then mildly panicked as I wasn't sure how to put the thermostat back in. It just sorts of plops into the hole? I'm sure on some video I saw someone prising it out with a screwdriver, so the plopping made me uneasy. On the other hand I didn't exactly have to lever hard to get the old one out. Tried putting the old one back, that just plopped at well, so plops it is.

Did it up pretty tight but super-careful not to crack the cover or strip threads. If a steel block and steel cover I'd probably give it a further half turn but I'd rather it leak and do the alarm thing, than break something.

So, filled the trusty tub, drank coffee... tried it.

Didn't leak around the cover. Cool. Let it run for a couple of minutes, still not leaking, pee stream was strong. Clambered out the boat and felt the stream, same "somewhat warm, warmer than the tub water" feel.

Fiddled with the carbs until I figured out how to rev it up, revved it up a bit.

Then just held it full-throttle - ROAR!

Interesting things happened.

First, it actually sounds a bit like a sewing machine?
Secondly, I couldn't get it to rev beyond 5000 rpm? Pushed the little widget as far as it would go, 5000. Wouldn't go higher.
Third, tried feeling the pee stream... hot. Not warm, hot. Not scalding, but definitely hot.
Fourth, feeling sorry for my neighbors and my wife working from home with Zoom meetings, I kept it roaring for about another 30 seconds, so I'd say about 50 or 60 seconds of total sewing-machine roar.

No alarms.

Currently waiting for the tub to empty before I go out there and put the cover and cowling back on.

Question - does this engine have a rev limiter or something, that stops it going nuts in neutral? I also tried the fast-idle thing from inside the boat, same thing, tops out at 5000 rpm.

Can't talk about which propeller, I mean it's in neutral? I was concerned about over-revving it but it actually refused to reach the redline. I'm hoping that's Honda being fancy, rather than something wrong with it?

I guess what I SHOULD have done is deliberately recreate the alarm at home in the tub, then see if the thermostat fixed it. But at this moment in time, as far as I can tell - it's fixed?

Of course what it really needs is another run on the river/sea, running under a real load for a longer period of time. For now, revving it as hard as I could for as long as I felt comfortable, it didn't overheat. Or at least no alarms or anything


Yeah I should still do the impeller too, which by the sounds of it is actually a tougher task than the thermostat. Must say though, it pees like a horse so I don't feel this is too urgent and I'm pretty sure it's not why it overheated.

Let me upload some pics, maybe a vid.

You know what? I feel like refilling the tub and doing some more revving... But I best get on with work and do that tomorrow....







A peeing vid:


Or go fishing tomorrow

[Drifter]

Sniffing around on the interwebs, I hear it's possible the tachometer is not set properly? But I'd presume at some point over the last 25 years, somebody would have noticed?

[Tomfoolery]

Take the prop off, put it in gear, then rev it.

Or plop it in the water and go boating.

Your call.

But it does sound like you’ve fixed the issue.

[Inquisitor]

Your writing is vivid... I'm not sure a video would be any clearer. I think Horse is better than Chihuahua.
I'm sure a Honda guy will chime in soon, but I sure would be surprised with the ability to rev-limit on a carburetor'd engine.

[Drifter]

Thank you kindly

On some other more general forums I read that depending on year, you need to twiddle some screw on the back of the tachometer or if a different brand then set it to #1 position, or some such thing. It certainly sounds like it's revving hard, yet as a new engine to me I don't know if it sounds like 6000 rpm or not.

I guess a mechanic would have some electromagic gun that could read the spinning engine. I don't have such a thing.

An actual test on the water is required I think, to confirm if it's cured the overheating, also to see if it's producing the power and speed expected of an elderly 50hp (I'm expecting around 16 mph fully loaded but empty ballast)?

Weather looks horrible again this weekend, fishing calendar doesn't look great, tides look impractical, so tomorrow I'll play in the tub again and if all goes well start prepping for the weekend after....

[Jimmyt]

My Etec is rev-limited in neutral. On the Honda, the ignition system can be used to rev limit, even with carburetors, wnhich is probably why Tom gave you his advice.

Those passages show me that the motor has lived in salt water and rarely been flushed.

The impeller is a bit more of an ordeal than a thermostat, by several orders of magnitude. After the first time, though, it's not too bad.

I would put an impeller in just so you know you have a good one and how old it is from then on. Then every 5 years (or whatever interval Honda recommends), you can do another one. They take a set after awhile and get less efficient. Not sure the telltale stream is a good indication of impeller condition - other than there is one.

So, put it in the water and give it a good test under load if you want. But be careful leaving an unknown age impeller in there.

[opie]

page 3-37
applicable???

[Drifter]

Mmm. That is relevant, yes. Thank you Opie.

Today I just fiddled around, and didn't touch the engine.

Drilled the holes in the rudders a little bigger so that my newly-arrived quick-release pins would fit (lovely fit through the rudder brackets but the rudder holes were too small). Mounted a fire extinguisher next to the head, fitted a 12 gallon spare fuel tank in the starboard bunk and drilled a hole for the fuel line (I plan to fit a Y tap to switch between them). Replaced the zinc under the engine, having discovered the original owner had a new one in the box of bits.

Bad news - in the box of bits I found a 2nd hand thermo-switch, a thermostat (can't tell if used or not) and a new internal diode.

Getting an uneasy feeling that the previous owner went through the same steps I'm going through, wasn't able to fix the overheating and so sold the boat..?

And I must have about 6 spare impellers, though only 2 actual kits with gaskets (and thinking about it, one of those is one I bought myself a couple of months ago, before finding the box.)

Right now am struggling to find the enthusiasm to pull the engine apart to fit a new impeller.

I HOPE all these spares are from the original owner taking loving care of the thing, and the more recent owner (MRO) being clueless and careless. The MRO, when I asked via the dealer, said the impeller was last changed 3 years ago.

Actually, didn't he also say he'd owned it 3 years?

So maybe MRO has done nothing in the way of maintenance, just passed on the spares that the loving original owner (OO) gave him?

One thing that points in that direction is the fact the lower anode was absolutely covered in barnacles and gunk, completely useless - but there was a brand new one in the box of bits, unused?

So hopefully the overheating is because both the impeller and thermostat are over 3 years old. Either that or MRO tried changing the impeller, thermostat, thermal switch and even the internal anodes, and then gave up because it still overheats

And while under the engine to change that zinc, noticed it's leaking hydraulic fluid.

*sigh

The tilt motor is fine but it does sound like the fluid needs topping up. I have no idea where to get seals for it or if they are still available?

Or how to change them.

One thing I have done is bit the bullet and ordered a service manual, $80 plus $40 from Amazon, which is cheaper than the $80 plus $80 shipping I was offered by some other place. So used the "spare" $40 to order some of that Saltaway.

I'm hoping a new plastic oil-can type thing I've seen locally will just about fit over the lower-end (about 19 inches or so). I might need to catch and re-direct the pee stream, but the plan is to change the impeller, then using that small volume of water, mix Saltaway in it and leave it running for 30 minutes, see if it can clean inside?

Bright side - if the OO purchased internal anodes, then he probably fitted them, at some point during the last 25 years. Which means there's a fair chance he greased the bolt threads. Which means there's a fair chance I can open it up for internal cleaning without breaking anything?

Think I can get away with liquid gasket?

[Tomfoolery]

Just remember that 5th bolt that holds the leg on. It’s either under the trim tab anode, or it’s under the intake screen; I just don’t remember now, but it’s in there somewhere. I put a floor jack under the leg when taking the bolts out, just so it can’t drop, but any stack of scrap wood will do of course. Or do it while it’s tilted all the way, but be careful it doesn’t drop. It’s not heavy, but it is somewhat delicate, being aluminium and all.

[Drifter]

I saw a video a while ago, where the guy says to use a pair of Molegrips (self-gripping pliers) to hold the gear-shift shaft, and stop the shaft dropping?

But i'm also told to unbolt the shaft?

I'm a little unclear if that shaft comes off with the lower unit or if I'm supposed to keep it attached to the upper unit, somehow?

Or use the Molegrips to keep it in place on the lower unit?

[opie]

Careful what you watch. Pliers on the shift rod seems dumb, you will stress the rod and possibly ruin threads. Stick with advice from your friends here. We've been through everything already.

[opie]

Tom's advice is good. After separating the shift rod, my own method is to remove 3 of the 4 bolts (10mm) on the lower unit and the single bolt (8mm) under the trim tab. Then carefully and slowly remove the 4th bolt (10mm) while supporting the unit. If you are lucky it will come apart. (I keep antiseize compound on everything for the next time.) If it is corroded together, soak with oil and take your time.

As for the tilt motor, the leak, hopefully is in the piston assembly and not the little motor pump. If you isolate and find leak, yes, common o-rings will fix leak. Let us know and we can provide more details and pics. Be sure to fill it up with transmission fluid and not oil. Fill hole is on side and not on top.

[opie]

To separate shift rod before beginning separation of lower unit, shift into reverse WHILE the admiral rotates the propeller. This will position upper adj nut and lower lock nut where you can get spanners on them.
They unscrew in the normal "lefty loosey" method. That means lock nut on bottom turns lefty while looking up from ground and adj nut on top turns lefty while looking down from engine. Be sure to count threads before disassembly so as to put it back correctly. (7 threads showing on bottom is approximate.)

[opie]

One more bad possibility........ sorry to even mention it..... but from page 6-10 of manual I referenced earlier.