1983 Mercury 18 Hp Bleed System, no check valves?

[2dbit]

I have been under the impression that all 2 cycle outboards have check valves as part of their bleed system. During rebuild, this engine doesn't appear to have any...just a hollow fitting on the cylinder, and another on the carburetor adapter plate. Am I the one missing something, or is the engine that's missing something...

 

[2dbit]

Re: 1983 Mercury 18 Hp Bleed System, no check valves?

Nobody?

 

[mcycleboy]

Re: 1983 Mercury 18 Hp Bleed System, no check valves?

I have a 1988 20 Hp Mercury with the same thing... no bleed check valves. The 2 nipples are straight through...no checks at all. The motor idles like crap but I have a hard time believing the this was a mere factory oversight. I have looked on the internet and can't find anyone else expect for your posting that has this situation. I know for a fact that my parts motor...a 25 hp a few years newer has check valves. Go figure ?

 

[2dbit]

Re: 1983 Mercury 18 Hp Bleed System, no check valves?

What bugs me is this: http://1manual.com/Mercury%20manuals/Service%20Manual%20PDFs/TwoStroke/826883r2/4.pdf Page 33 has the location and the check of the checkvalves. It's our engine block! Where are the check valves?!?! I wonder if there are some small in-line check valves we can put on the hoses...

 

[Laddies]

Re: 1983 Mercury 18 Hp Bleed System, no check valves?

The reason there is no check valves is in most bleed systems the hoses go from 1 crankcase area to another and both areas have pulses, on the 18-20+25 the bleed lines go from the crankcase area to the intake ahead of the reeds, no pulse just vacuum so there is no need for a check valve.

 

[2dbit]

Re: 1983 Mercury 18 Hp Bleed System, no check valves?

Laddies, thank you for your answer, always like to hear some insight into the reason behind some of these systems. I went and looked on this motor and found that the bleed goes from transfer port, over to crank case. It is ported to the crankcase side of the reeds and has no check valve. To me it would seem that during intake stroke it would be pulling air from the transfer port area back to the crank case...In this instance wouldn't it be favorable to have a check valve installed to prevent back flow to the crankcase?

 

[Laddies]

Re: 1983 Mercury 18 Hp Bleed System, no check valves?

I don't have a 18 in the shop to look but all 18-200+25 that I've seen the bleed lines go from the transfer port area or crankcase to the 2 fittings on the reed block cover below the carb, I just looked in the manual and the flow is backwards to what I said in my first post excess oil that has puddled in the manifold area before the reed block is sucked thru the lines to the transfer ports. Sorry for the misinformation.

 

[2dbit]

Re: 1983 Mercury 18 Hp Bleed System, no check valves?

Here's a pic that will make it a little clearer as to what's going on with the actual motor... So, I guess what it comes down to is...should I be looking for some sort of small inline check valve to put on here to help the idle?

 

[2dbit]

Re: 1983 Mercury 18 Hp Bleed System, no check valves?

I almost feel like I should contact Mercury and say...what's up?

 

[Laddies]

Re: 1983 Mercury 18 Hp Bleed System, no check valves?

I bet the engineering dept would like the help on a 28 year old motor. If your engine can't live without them heres a link for a newer model 20 with them, item # 15. http://www.ishopmarine.com/ishop/js...cCatFilter=MM&eCatSupFldr=supplier-050-025-MM

 

[2dbit]

Re: 1983 Mercury 18 Hp Bleed System, no check valves?

ha ha, Yeah, I bet Mercury would love to support the 28 year old motor as well...oh wait, it seems that they 100% move on as soon as the new model comes out...

 

[Laddies]

Re: 1983 Mercury 18 Hp Bleed System, no check valves?

That's what new models do fix problems on the older models for product improvement.

 

[matth121]

Re: 1983 Mercury 18 Hp Bleed System, no check valves?

now I'm wondering if i have them. I just replaced those lines but didnt think to check for the check valves. Mine idles fine though. I'd think that vacuum would be enough to pull the fuel from beneath the reed block, but would also imagine that when you shut down, with no check valves, wouldnt it run back down the lines. But if Laddies says our models dont require them, that's enough for me, he would know.

 

[matth121]

Re: 1983 Mercury 18 Hp Bleed System, no check valves?

just checked my seloc manual(groan), nothing mentioned about check valves in it. Even the exploded parts diagram shows the fittings the hose attaches to but no mention of check valves. Hope this helps.

 

[2dbit]

Re: 1983 Mercury 18 Hp Bleed System, no check valves?

What Laddies says is true, with each year that goes by the manufacturer improves on their designs. With our older motors there were no check valves, but on the later models without any other change to the block they now have the check valves. In the grand scheme of things it probably doesn't make a big difference but I'm going to consider those check valves as a design improvment. Lets just call my motor Pre-Mod...soon to be Post-Mod.

 

[2dbit]

Re: 1983 Mercury 18 Hp Bleed System, no check valves?

Checkvalves: I'm a believer. If your motor does not have check valves installed. Get them. Well, get them if you want a more stable idle at least! I have completed my engine rebuild and kept it in 95% factory condition. I say, 95 because I installed composite reeds, which probably helped the idle issue in addition to correcting the other problems my engine had (bent reeds, displaced seals, etc) But to determine if the check valves should stay or go, I ran the motor at first without the check valves(factory condition). I gave it a good 3 or so hours of break-in time before cutting the lines and installing. What a difference! Now mind you, the idle before the checkvalve installation wasn't bad. I mean the engine would shake a lot but was in no danger of dying. The checkvalves smoothed the shake out a lot. It still shakes (to be expected with a 650-750rpm idle) but it's a lot smoother. I would have liked to install them closer to the reed block, but since this is something I'll have to include in maintenance from here on out, I had to take that into consideration when deciding where to put them. Well, as I said...I'm a believer. I included pictures of how I placed them incase anyone was curious:

 

[SiuslawSlim]

Re: 1983 Mercury 18 Hp Bleed System, no check valves?

Maybe someone can lend me a hand concerning the fuel issues my outboard is having. Mine is a Canadian 1986 25xd hp with a WMC11 carb. I cannot seem to get it to run without pumping the primer ball on the fuel tank line. I have rebuilt the carb, and double checked the rebuild. All seems well with the rebuild. The float is set right, the diaphragm is good. I have checked the flow from the remote fuel tank through to the carb, and all is flowing well. The filter is clean. The hoses do not leak anywhere. I might add that all of the electronics have been replaced with brand new: stator, trigger, switch box and coils. But that was done because the DVA showed uneven voltages and bad ohm tests on the coils.

The motor will idle fine and never die. I can run it at high r's in the tank forever and it never dies. But the minute I put the silly thing in the water, put it in forward, it will run like a raped-ape until it drains the bowl (for about 200 yards): at least that is what I think is happening. I am wondering if the bleed hoses are defective, or if there is something wrong with that system? Is it the bleed hoses that provide the vacuum that operates the diaphragm in the carb.? That is my understanding. Is there some way to test the hose vacuum. Or am I just on the wrong track with the hose issue? It seems strange that with good flow from the fuel tank, and a rebuilt carb I need to pump the bulb to keep it running. I sure would appreciate a helping hand on this one.

 

[SiuslawSlim]

Re: 1983 Mercury 18 Hp Bleed System, no check valves?

Can anyone tell me what mechanism or method is used to actuate the fuel pump diaphragm in a WMC11 integrated carb? I am starting to doubt my sanity on this one. The salmon are biting and I'm stuck on shore. Maybe feeling a little bit sorry for myself as well.

 

[2dbit]

Re: 1983 Mercury 18 Hp Bleed System, no check valves?

Siuslawslim, I don't hold the experience that you'll find with other members of this board, but to me if it idles fine but once you have it in gear the rpms drop so low it barely runs, sounds like you might benefit from just bumping up the idle rpm a few... Have you checked with a tachometer what the rpms are both in and out of gear?

 

[2dbit]

Re: 1983 Mercury 18 Hp Bleed System, no check valves?

matth, Crowley Marine: VALVE-CHECK (#149126) I am willing to bet you can find it cheaper elsewhere, but it was on that site that I bounced around part numbers till I found something that I was pretty sure would work (got lucky...it did...) http://www.crowleymarine.com/parts/164682.cfm