Exhaust

[BigWeakSauce]

Good Morning! Had my 1974 Mercruiser 165 running on muffs yesterday and noticed decent water flow coming from my prop but very little solid water coming from the exhaust holes on the gimbal ring, when I put my hand up to it I was getting sprayed with fine mist that pretty quickly wet my hand but wasn't sure if water should be spraying like a hose from there or if a fine virtually invisible mist was sufficient.
My temp gauge was reading beyond it's 240 degree max which is why I'm looking into water flow however I suspect the gauge/thermostat is faulty because upon cutting the engine with the key still on it immediately drops to 180ish and stays there even when the boat is off with key out and battery removed. When I come back to start the boat hours later the gauge restarts at 0 again but only after turning the key to on.
Any insight here? Is that light mist from the gimbal holes OK or a bad sign?

 

[nola mike]

Usually on muffs the water will preferentially exit those relief holes, but also the prop. Need to verify your temps, start with an ir gun. I'd also disconnect the water hose after it enters the boat and quickly get an idea of how much water you're getting from the impeller. Hard to say what's actually going on. (Is your temp gauge reading after you shut the boat off but after you turn the key back on?)

 

[BigWeakSauce]

Hard to say whats going on with the temp gauge, yesterday when I started it up is when I noticed it was still stuck on 180ish from the day before (battery disconnected all night), dropped as soon as I turned the key to ON. After starting it slowly started creeping up from its lowest reading seemingly working just fine. Dropping from like 240ish to 180 instantly upon cutting the engine doesn't make sense to me. Didn't get to run it all the way back up yesterday because I flooded the engine after it cut while revving... dealing with a reverse issue at the same time here and got my cable adjusted to how I think it needs to be but may have messed up the reverse interlock or interrupter in the process (causing the engine cut).

But for the water when you say to remove the hose you don't mean with the boat running do you? Are you saying cut the engine, remove the hose and see what happens as water drains?
I have the Seloc manual but I can't figure out where those relief passages originate, concerned there may be some 20 yr old gunk in there. There is significantly more water coming out of the prop than those relief holes.

 

[nola mike]

No, have it disconnected briefly with the engine running. Can't imagine that crud would clog those holes, but IDK. They're large bore with positive pressure all the time, so I wouldn't think it's likely. Your temp gauge only works in the key on position, so disregard everything with it off. Cut the engine, then turn the key back on. You should be right where you were before you cut it. The passages are just going through the transom plate through the Y-pipe (I guess no Y on the straight 6). Sounds like you have a legit overheat though.

 

[achris]

All marine instruments (well, the good quality ones anyway) are what we call 'unsprung'. The upshot of that is that with the key OFF (the instrument unpowered) the needle is free to float anywhere it so desires. Once the key is OFF, none of the gauge readings are valid. What an instrument shows without power on it is completely invalid.

Good Morning! Had my 1974 Mercruiser 165 running on muffs yesterday and noticed decent water flow coming from my prop but very little solid water coming from the exhaust holes on the gimbal ring, ...

Any insight here? Is that light mist from the gimbal holes OK or a bad sign?

For the design of those gimbal housings, what you are seeing is completely normal.

However, 240 degrees is not. You need to find out if that's an accurate reading, and if it is, find out why it's running so hot.

Chris......

 

[BigWeakSauce]

Any advice for getting that reading/tools to read with? Can the tools be rented anywhere?

 

[Rick Stephens]

An infrared gun type thermometer is so cheap these days it is worth the small expense to start your investigation by purchasing one. They will have them everywhere - auto parts stores, Amazon, FleaBay, you name it. These guns are super simple to use, point and get a temperature reading where the laser hits. Great way to get a second opinion on temperature readings. Point at the temp sender on the thermostat housing and confirm it is reading right.

 

[BigWeakSauce]

Update for you guys and a question... I put her into the water this afternoon for the first time since I got her, and she floats!!
However we overheated quickly and this time discovered NO WATER FLOW whatsoever!! Pulled the thermostat housing and discovered there wasnt even one in there, previous owner must have removed it when winterizing. And on that note the whole system still had antifreeze in it!! I ran her at home on muffs and had water exhausting through the prop (only slight liquid through relief holes), how on earth can water exhaust through the prop without entering the engine? All passages still had antifreeze in them, indicating none of my hose water ever made it into the engine...
so the overheat is clear, no water flow. But I changed the impellar just before winter and with the muffs on you can tell its pulling water into the stern drive... when I disconnected the water inlet hose from the Tstat housing, I poured water down to check for blockage and it immediately drained through the lower unit (thru where the impellar pulls water in).

could my brand new impellar seriously be failing?? Could the engine circulating pump be to blame?
i'm at a loss...

 

[achris]

At a quick guess, you missed the water tube when you put the drive back together.

 

[BigWeakSauce]

Another drop of the lower unit in my future! And of course it's 40 degrees today so getting the lube out will be a real treat.
Has to be that water tube tho, not sure how else water can essentially back feed and discharge through the prop before getting to the engine.

Thanks for looking at this guys, I'm nearing the finish line on the restoration! side note, anyone have experience running without a thermostat? I have to replace the gasket anyway so I'm going to put a Tstat in but until I have the water flowing I was going to leave it out, can't really cause any harm right while testing?

 

[achris]

Just pull the entire drive, loosen off the nuts, then lay the drive on its port side (that keeps the oil passage up, as it were). You can now remove the nuts and slide the drive apart, realign the water tube and put it back together.

Not sure why 40 degrees would make the oil hard to get out, at that temperature, it'll flow quite easily. But you don't need to drain the drive at all.

... side note, anyone have experience running without a thermostat? I have to replace the gasket anyway so I'm going to put a Tstat in but until I have the water flowing I was going to leave it out, can't really cause any harm right while testing?

Not recommended to run without a thermostat. As it's sea water cooled, the engine can run way too cold, increasing both wear and fuel consumption, and it can run at an uneven temperature, meaning some cylinders are warmer than others, and that's never a goo thing either.

Chris......

 

[nola mike]

Just pull the entire drive, loosen off the nuts, then lay the drive on its port side (that keeps the oil passage up, as it were).



Chris......

Lay it on starboard side? (Port side up)

 

[achris]

Lay it on starboard side? (Port side up)

Oil hole is on the starboard side. You want the hole high, lay it on the PORT side!

 

[Bt Doctur]

To the confused about P and S looking at the rear of the Alpha drive the the oil transfer is on your right side

 

[nola mike]

Oil hole is on the starboard side. You want the hole high, lay it on the PORT side!

ok, someday I'll learn my left from right

:facepalm:

 

[Simoniz]

Another drop of the lower unit in my future! And of course it's 40 degrees today so getting the lube out will be a real treat.
Has to be that water tube tho, not sure how else water can essentially back feed and discharge through the prop before getting to the engine.

If the water tube is displaced, then water pumped by the impellor will enter the exhaust passage in the drive, instead of going further, through the uppper unit, hose transom to the engine.

 

[BigWeakSauce]

If the water tube is displaced, then water pumped by the impellor will enter the exhaust passage in the drive, instead of going further, through the uppper unit, hose transom to the engine.

This issue has officially been resolved! When I replaced the water pump in the fall I didn't realize the seal in the upper unit for the water inlet tube had come out with the tube when I dropped the lower. Luckily I hang onto all my junk parts for a little while after doing a job and found that seal, it was broken. But a few days earlier I snagged a free junk boat that had the same pre-alpha drive on it and was able to harvest the seal from that unit. Before when reattaching my lower unit I had the copper tube in the water pump housing as I tried to lift the lower into the upper and had a heck of a time trying to align everything (water tube hitting the edge of the passage). With the seal properly installed I was able to put the water tube into the upper first and use the guide tube in the water pump as intended!! I was wondering why no one on youtube seemed to be having as much trouble reassembling as me.
Now she's pumping water like a dream and properly exhausting water through the relief holes, no thermostat in place so the engine never really reached 120 but I only had her on muffs for about 2 or 3 minutes of run time, same amount of time it took to overheat previously.
Upon trying to start her up tho I discovered an air leak where my fuel line slips over the fuel pump inlet fitting (took a few hours to diagnose that), fixed that real quick and now we seem to be in real good shape!

Thanks for all your help guys!

 

[achris]

Put a thermostat in that engine...

Your free 'junk' boat, which 'pre-alpha' drive? (there's 17 drives that came before the Alpha One)

Chris.......

 

[BigWeakSauce]

I have a thermostat kit coming, hopefully today. Shredded the gasket when I popped off the housing so it's leaking a bit. Tstat kit probably annual Spring maintenance job when flushing winterizing fluid? Have to imagine that gasket will tear every year I go to pour new antifreeze in.
Not sure which pre-alpha now that you mention it but it matches the one I have on my 1974 165 IL 6. Took it off a 188hp Mercruiser V8 (888 I believe), circa 1977-1979 according to previous owner. U joints completely rusted on it due to owner leaving a gap between the drive shaft and engine for a few years, exposed to weather. Lower was in excellent shape internally.

 

[achris]

Probably a MerCruiser-1 drive (MC1 for short)...