Acid flushing vs Poppet valve (PCV)

[DennisG01]

Just wanted to run something by you guys to see if I'm correct in my thinking...

This past weekend, I pulled the boat out of the water for the season (salt water - Maine). Before I flushed it with fresh water, I pulled the t-stats and the PCV to check the condition and for any salt build up. For the most part, they were pretty decent - just a little build up underneath the t-stat, but not horrible by any means. The t-stat housings were very clean and the only slight issue with the PCV was some salt around the edge of the hose where it attached to the PCV housing (but I couldn't feel any salt inside the hose when squeezing it).

Anyways, I decided to do a flush with Rydlyme and did so by removing the t-stats and PCV. I circulated the Rydlyme through the engine for about 3 hours using the flush port on the side of the engine. When it was done, I took another gander inside the t-stat housing area and they were exactly the same (still some small chunks of salt residue) - as if the Rydlyme never even entered the t-stat area.

Then I thought... maybe I made a mistake by doing this flush with the PCV removed? With that removed, would that have prevented any acid from being pushed to the top of the block? Did the acid simply flow into the bottom part of the block and right back out?

[TownsendsFJR1300]

With the PCV removed, it's letting water out (basically like it's open with too much water pressure).

So yes, put the PCV back in and re-do...

For S&G's, as is, just use water and see if even makes up to the thermostat area with the the PCV OUT. Then put it (PCV) back and and check again...

Dollar says you see MORE water (if not coming out at the thermostat).

I'd also close off (tape) the pisser (at least for a little while), just to keep more water/Rydlem in the power head.

Are you using a small pump and a large "catch pan" or did you remove the LU?

Please post back how it goes, maybe a pic or two? (before and after)..

[DennisG01]

Thank you, Scott, for the reassurance. Yes, I'll re-do it again in the Spring. I did take "before" pictures. But didn't take anymore yet, since there wasn't any changes.

Still can't get the lower unit off. I tried everything. It'll have to stay on till the impeller needs changing. Then I guess I 'll have to cut a hole in the side of the mid-casing and sawzall the driveshaft in half. Wonderful.

I used a plastic 55-gallon drum, put 6 gallons of the Rydlyme:Water mixture in it. Then, I just wrapped the engine with a sheet of plastic, starting just above the pisser. I made sure the plastic was inside the drum so that any places where water would exit would be captured by the plastic and directed back into the drum. I hooked a bilge pump to the engine flusher on the side of the engine.

[TownsendsFJR1300]

Interesting...Thanks Dennis.

Re the LU, I understand cutting the drive-shaft so the LU drops.

But NOW, you have a short stud/stub/splined drive-shaft end you have
to reach up and even just get to.. And you need a new drive-shaft along with
all the work to replace it.. (I would think it'd be somewhat hardened)

Is the procedure, then, to use an air chisel, knock it upwards,
to try and loosen it???

What am I missing???

[DennisG01]

I haven't thought it fully through, yet. But, yes, that's pretty much what I'm thinking. I'd cut it as low as possible (to make reaching it as easy as possible). And then, yes, knock it UPWARDS a tiny bit to hopefully break the corrosion. Once the lower unit is off, I may be able to some penetrating fluid or Rydylme on it to help.

Luckily, I happen to have a spare engine. It has one bad cylinder, but the rest is good. I've already used the stator from that one, but the rest is still there. So if I can get the lower off, I can just slide the spare LU back in. Maybe I would replace the mid-casing with the spare mid-casing, maybe not. A hole on the side, with a plate epoxied on wouldn't bother me one bit, though.

[TownsendsFJR1300]

You didn't happen try running the engine (on muffs) with ALL the LU bolts out did you?

Someone mentioned it before, with the vibs, etc. I'd also spray (with penetrating lube) where the LU meets the mid section, especially where the
SS alignment pins are..

You may not mess with it this year, but I'd soak it, can't hurt...

[DennisG01]

No, I forgot about that suggestion. But I can try that next year. Yeah, soaking is a good idea. I "think", though, that the problem is definitely higher up since I can get some separation between the lower and the mid. I can get more separation (using wedges) at the aft end - about a half inch. It's the front edge that isn't budging much (although I can get a "crack" started). Which makes sense since the driveshaft is at the front end.

[TownsendsFJR1300]

I'd think, if you "worked it" up and down, while idling, (maybe a sissor jack under the skeg), especially if you have a little bit of play, you may luck out...

Heck maybe a short rev or two wouldn't hurt. Same with pressure inbetween the mid section and LU..

Next years project!!

[exeter27]

DennisG01. I lived in Freeport Maine for 30+ years - and have relocated to NH. I know your pain with corrosion locked driveshafts. I had a 50 HP Mercury that was in the same state as your engine. Prior owner had parked the boat for multiple years (obviously not removing LU periodically) and it got locked together. Because I had time (I was repowering my Whaler), I removed the Mercury and stored it in my shed on its 'head'. Upside down allowed me to spray lots of Liquid Wrench and PB Blaster onto the driveshaft in the small hole that I got drilled in the mid section just below the block. That spray could then trickle down to the head/block where the corrosion was.

I did all the tricks including removing the bolts and running the engine to no avail. I also put in shims to put downward pressure on the crank - and then ran the engine. I put thicker shims - but created a tightness on the crankshaft enough so that the starter motor couldn't turn over the engine!

That's when I decided to let it sit on its head. After a couple of months - I went back to it, and with shims, some heat and banging in strategic spots (careful, cast aluminum is very brittle) was finally able to remove the LU.

Probably not that easy with an OX66 - but you do have time. If you can find a friend to remove the engine - store it upside down and let time and penetrating spray have at it! Salt water is so tough on stuff....

[DennisG01]

Thanks, Scott - will definitely keep that under advisement and can easily check back into this thread to remind me.

Exeter - I never thought of turning it upside down - interesting idea! I don't have the space (overhead lifting points) to do this at the cabin, though... especially since it's a 500lb+ piece. Just a little harder to do than a 50! I suppose I could build an overhead A-frame/hoist easy enough, but rolling the engine back to upside-down without damaging anything on the side of the motor would worry me a bit (although 2 come-a-longs should do the job without the engine ever touching the ground). Gonna think about that, though! Maybe I can still drill/cut a small hole and spray in there - since penetrating fluid will "creep" uphill, at least to some extent. Thanks!

[DannyMart]

I attempted to do a preventive descale flush of my starboard 2005 200 HPDI, which was running a little warmer than the port engine. The complete water pump kit, PCV and thermostats were changed this past July and I had put only about 10 hours on the new parts.

I pulled both thermostats, but left the PCV in place. I used a 40 gal/min 115 volt submersible pump to circulate 9 gallons of 5% vinegar with a 25 gallon plastic storage container under the lower unit to catch the fluid coming out of the motor and tell tale. I took pictures of the thermostat housings before starting the flush. I planned on a 3 hr flush using the fresh water flush hose attachment to the pump and checked on the progress after 1 hour. A good stream of vinegar flowed out of the tell tale hose, but the thermostat covers were bone dry. The vinegar in the container was slightly cloudy, which I think indicates that some scale was dissolved. The thermostat housings had a moderate amount scale. I connected a garden to the flush attachment and after a few seconds, water poured out of the thermostat opening, so the cooling passages weren't completely blocked. I didn't run the engine with the thermostat housing off as I was afraid of creating a short.

I am considering purchasing another thermostat covering and attaching a male hose bib attachment to the covering so I can flush the upper portion of the cooling passages with the pump. I put the thermostat coverings in vinegar for 30 minutes, which didn't do much for dissolving scale, but the rock hard scale was soft after the soak and easily removed with a screwdriver and dental pick. I'm going to use Hammerhead descaler the next time.


Does anyone think that pumping into the thermostat opening will create problems with getting descaler into the cylinders?

[TownsendsFJR1300]

Water flow normally runs there, it's all part of the cooling system..

Just remove the thermostat for your procedure. Replace cover.

As it (T-stat) stays closed unless the engine is to temp, water flow to one side is VERY LIMITED.

I'll flush with muffs on, engine running until it gets to temp (and the T-stat is open).

[DannyMart]

I was going to run the engine long enough to get the block to normal running temp before starting the flush and warm the descaler to 110°F to get the reaction to run a little faster.

[zenoahphobic]

I was going to run the engine long enough to get the block to normal running temp before starting the flush and warm the descaler to 110°F to get the reaction to run a little faster.

Good idea to warm everything as chemical reactions work more effectively. This topic comes up often, never read anyone suggesting this before.

[99yam40]

even at 110 the stats will close off, better to remove while circulating the chemical