Ticking sound from empty remote oil box 2.5 Merc

[scyc]

My 2000 150hp (2.5l) carb'd merc makes a ticking sound somewhat sounding like a misfire, but I'm scared it could be something worse.

So, my remote oil tank got bad crack in it which leaks everywhere. I know this might sound dangerous, but I leave it empty and just fill the motor reservoir every day for now.
All the oil lines are still connected to the motor so it still creates vacuum in the tank.
The other week I noticed a ticking/pinging sound emanating from the remote tank. I put my ear up to it and could clearly hear the noise which has to be coming from inside the crankcase.
I know for sure my motor misfires at idle because im in dire need of a carb rebuild and I pulled my reeds and the gap is about 0.005 away from being out of spec.

I'd like to think I'm just hearing a misfire and its not a crank bearing or a rod knock.
The pinging seems to be singular and in sync with a misfire, but I just can't be sure.
I would think a way out of gap reed valve would not make such a noticeable sound, either?

When I pulled the carbs/reeds a few months ago I rotated the flywheel slowly with the plugs removed to see if I could hear or feel anything noticeable, but It seems smooth and everything looks beautiful on the inside.

My questions are:
1) Does this just sound like a misfire, or perhaps something worse and more involved? I about to invest some money into the motor to replace the reeds, and to rebuild the carbs/fuel pump.
But I'm worried this motor might just be a ticking time bomb...

2) Is there a way to check for play when the reed cover is off and the crank is exposed?

Obviously, when I fix the reeds/carbs and fix my misfire, I'll be able to scratch that off the list, but until then this has got me worried.

Any suggestions would be greatly appreciated!

[XstreamVking]

Prob the oil tank pressure system check valve clicking when the tank can't build air pressure. There is an air line going to the crankcase check valve fitting from the oil tank. Plug it or replace the bad tank. Star side of motor, lower block area is where the check valve is.

[flabum1017]

Better be careful, that can cause the bilge to fill with explosive air/fuel mix and a ticking sound will sound good compared to a loud boom when the boat blows up.............

[vnemous]

Dont you get an alarm when the level goes down on your oil tank?

[mn808gade]

the crankcase builds pressure not vacuum in the oil tank,if run unsealed it would mean motor runs lean and coughs.check check valve operation (2# ithink) replace oiltank,then check pressure at operating speeds to merc manual specs.P.S.correct pressure is dependent on cylinder compression and checkvalve operation.backfires- can damage fuelpump diaphrams.--th

[scyc]

Thanks for the replies.

I had no idea about the check valve but I saw it and checked up on it after you mentioned it.
I got a new tank and I'm going to hook it up and see what happens next.

When I said vacuum in my original post, I generally just meant it held pressure. In actuality, the leak was not as bad as I thought, it just looked a lot worse because of the oil slick on my floor. The tank did hold sufficient enough pressure, though. I understand how it creates pressure in the crankcase and pushes oil through to the motor reservoir, but I'm trying to understand how it would run lean if there was a leak in the line? Too much air getting in from a leak, perhaps?

Sadly, from unscrewing the cap on the reservoir so often the cables cracked and came apart, so no low oil alarm for now...but thats next on the list.

I would not be surprised if this issue has caused my fuel pump diaphragm to mess up, (probably whats causing my misfires) but I'm ordering new reeds, fuel pump and carb kits tomorrow. When it's all together I will test the fuel pressure and oil tank line pressure (2# if you suggest but I will crosscheck what the manual says) and then post my results in a week or so.

I should note I did a compression test a few months ago over the summer and they all read 110psi dead even. I thought this was a tad low compared to other motors I've had, but this is only my second merc (my '04 150 EFI was about 115-125psi).

Again, thanks for the input its greatly appreciated!

[Dave Strong]

Should have just spent 10 bucks for a oil injection delete kit and be done with it. Premix and never worry.

Dave