Holes in J15RLCOB 15 HP carb chamber?

[Gizmobreaker]

I am rebuilding the carburetor from my 1985 15HP outboard. I keep it because it is the only motor that will fit through the cutout on the transom of my 1976 Catalina 27. While I was cleaning the body, I noticed little defects in the casting, in the floor of the chamber under the large removable plug. There are 3 drilled holes that are exposed by the throttle plate, but there are 2 smaller irregular holes that look like maybe there was air(?) in the casting.

The reason that I am rebuilding the carb is that I have a problem (of course). The engine starts fine and idles well, but not at very low revs. If I keep the revs up, the motor runs fine. However, if I am letting it warm up while I do other things, sometimes it stalls. Then I cannot restart for about 15 or 20 minutes. Either the motor has to cool down, or the engine is flooded; it's hard to tell which, with the motor on the back of the boat. Then is starts fine and I run the revs up and try not to idle. I have the side-mounted idle knob set at a very high setting and have always had to do that in the 8 years that I have owned the motor (and the boat). In fact, I have carved a little of the idle stop arm so that it can go farther than designed.

I run a 50:1 mix and the plugs are always dirty and a bit wet. Not soaked, but wet. I always disconnect the fuel hose and let the motor run out of gas. I keep it tipped when I am not on the boat. Even so, there is always a bit of fuel in the motor casing, under the carb.

I installed a new fuel pump, recently, plus a new hose and tank. Apparently, one should remember to only remove the 2 long screws when taking the fuel pump off while sitting in the dinghy behind the boat....

Are these holes a problem? I don't want to fill them with anything that might break off, later, and cause another issue. I thought about JB Weld but these are really tiny holes. Getting the epoxy into the holes would be a challenge. Something thinner would work but I don't know what would stay put.

I think that I have successfully uploaded 2 photos showing the holes. View attachment Carb Top a.pdf View attachment Carb Bore a.pdf
It's a bit hard to see the holes in the bore, but they are easy to see in the chamber on the carb top.

Thanks for any help you can provide.

 

[flyingscott]

I would not worry about those. But make sure the carb is clean. The 3 holes are supposed to be there.

 

[Gizmobreaker]

Thanks, Skipper. I appreciate the response. The carb is super clean. I soaked it overnight is SeaFoam, then blew it out with compressed air. Gently ran the holes with undersized welding nozzle reamers, just to make sure. (I removed no metal.) New needle. New gaskets, plugs, etc. from the rebuild kit. New bowl - there was rust inside and outside.
Keeping my fingers crossed. I would like to use the boat, this weekend.

 

[oldboat1]

Think I would tune that motor in a barrel before mounting it back on your Catalina (Maybe already the plan.) I would check its temp first -- make sure it's not overheating. The water level needs to be about six inches above the pump location, so sink the leg deep in a test barrel. The same is true on the boat -- sounds to me like it could be too shallow, based on the issues you describe. Additionally, you may be due for a new impeller.

The small holes under the domed expansion plug belong there, as indicated, and need to be clean (appears they are). Additionally, the hole that accepts the needle needs to be clear -- should get a peek at the needle point with the plug removed and the needle in place (good to check). I'm unable to speak to the larger opening up there on the top, offhand, as my '85 is tucked away at the moment.

Anyway, once you put the domed plug back in place, test run it and set the idle mix needle (carb) and the throttle idle on the side. Start with the needle about 1 1/2 turns open, and adjust from there -- would also set the idle stop down low, and control throttle setting manually while tuning. That motor should idle low and slow when it's running right, and should shift in and out of gear smoothly with no stalling. Cold starting should not be an issue, although you may have to set the idle mix needle slightly richer to start (maybe 1/4 turn), then return to the original setting when the motor warms up. The choke obviously has to work, with the plate fully closing.

 

[Gizmobreaker]

Hi Captain,

The motor is still on the boat. I removed the carburetor and took it to work where there are more tools and no water to drop small parts into. Given that I am on a mooring and have only an inflatable dinghy, the motor is a bit of a pain to mount and unmount. I've done it but I don't like it. I'm always afraid that I will drop it in the water.

I'm pretty comfortable with the water level. The Catalina 27 was designed to work with this motor (which is why no other motor will fit and tilt, darn it). It is a 20" shaft version. The impeller was new, this spring and the telltale stream is strong. The water from the telltale never gets above warm (how's that for a specific temperature?). Occasionally, an insect will get into the telltale but I can always clean that out.

The 3 holes are very clean. The other 2 holes are also clean but I assume that they leak fuel into the chamber. That was the inspiration of for the query. There was a small piece of black debris (probably decaying fuel hose - darn Ethanol) in the needle valve hole but I go that out. The needle is brand new and can be seen extending through the metering hole.

I won't be able to put the carb on the motor until Saturday, when I will follow your instructions for tuning. It has never run slow at idle; not in my garbage can at home, not on the boat, and not in the tank at the boatyard. Does not matter if it is cold or warm; if it is in neutral it does not run slow. The idle stop always has to be in to the max if you don't want the motor to stall. Cold starting has never been an issue. It has not stalled when shifting, except for a period, a few years ago, when the timing plate was loose.. The idle needle was set at about 1 turn out. Maybe it just needs to be more open when it is warmed up and the metal parts expand a bit.

I have some concerns that it is flooding, rather than getting too hot. The time delay that allows the motor to cool also allows fuel to evaporate. On the other hand, if there is a defect in the impeller, running it faster might pump more water through the engine. Hard to tell what direction to go. I suppose it could also be the thermostat - the telltale bypasses that,

 

[oldboat1]

Well, carb work might do it. When it's warmed up, should be able to hold you hand on the top of the head for a few seconds, or use an infrared tester (look for about 140 more or less, no more than 160F).

 

[gm280]

Gizmobreaker, I looked and read this entire thread, and I think others may not have seen the holes you were concerned with. Yes there are three purposely machined holes in the throat of the carb. And there are used during the idle circuit and just very partially opened throttle plate. But your arrows are pointing to two other holes. And I think those are the holes in question if I am correct. My question is this, have you taken one strand of copper wire from a regular stranded wire and tried to push it into either of those holes you are concerned with? That would see if they were merely closed holes or holes that did protrude through into the body of the carb. Using one strand out of copper stranded wire won't harm anything but will allow you to see if they are through holes or not. If they are through holes, then you do have a carb problem and it is not going to run properly at idle. They would allow too much fuel verses air if they go into the fuel circuit and that will not idle correctly. JMHO!

 

[Gizmobreaker]

GM, that's exactly what I'm concerned about. One hole is very small and I can't get anything through it but I'm pretty convinced that it is, in fact, a through hole. The other one is larger and I can get a wire through it. The question is: What can I do about it? The holes are quite small and I don't want to put something in there that will break off later and wind up causing a bigger problem. It's way too small a space to do any welding, even with TIG. Do I have to junk this carburetor and try to find another in better condition?

 

[WernerF]

The area of these additional holes in not that large compared to the three intended holes. So the additional fuel flowing here will be very limited. I think the idle mixture adjustment can compensate for that.
If you want to plug these holes I suggest some copper wire thin enough you can stick it a bit into the holes but thick enough it won't go through the holes completely. Apply some screw lock to the wire, stick it into the hole and tap it flat with a punch and mallet.

 

[Gizmobreaker]

I like that idea. Kind of like rivets. And if any sticks through into the throat, I can file it smooth. Gently. Thanks, everyone. I've got a plan that does not involve finding a new carb. I'm grateful.

 

[gm280]

Gizmobreaker, you could mix up a little JB Weld and put some in each hole and then smooth it out. It would stay because it would probably splay some on the inside and keep it from coming out again. JMHO

 

[Gizmobreaker]

The carb is back on the motor. I replaced the starter rope and the rope bushing, as well, since they were both getting a bit tired. The motor runs great. It idles very slowly, for a change, too.
I did not plug the small holes. I ran out of that size core plug and my dealer had none in stock.
I think I will buy a new fuel hose every other year instead of every 4th year, from now on. I could see small black bits in the carb which I imagine are from the hose degrading.
Thanks, everyone, for all your assistance.