Tight shifting from neutral to forward or reverse, 1979 OMC 120

[anderso8623]

Re: Tight shifting from neutral to forward or reverse, 1979 OMC 120

Boomyal, that screen you are speaking of, the one that you no longer have, is that the one you can see in my pix (look for the duct tape residue) or is it an internal screen?

 

[Boomyal]

Re: Tight shifting from neutral to forward or reverse, 1979 OMC 120

the upper and lower are not connected on a stringer - they are 2 separate compartments

....and have two different set of fill/drain plugs and top vent plugs. Anderson, if the lube in the upper gearcase (the one with the dipstick on the vent plug) was milky then be sure to pressure test it.

Boomyal, that screen you are speaking of, the one that you no longer have, is that the one you can see in my pix (look for the duct tape residue) or is it an internal screen?

The lube filter/screen that I speak of is internal in the lower drive. I believe the picture that you refer to is simply to filter large debris out of the water that is being drawn up through the water pump impeller. There is no shift action going on in the upper case where you were looking at the dipstick. The screen I speak of supposedly protects the pump that aids in the shifting, but is prone to plugging up and starving the pump.

Where are you located?

btw, you also want to lose that whale tail. It is very hard on everything. If you need some better stern lift, get some SmartTabs. They work miracles.

 

[anderso8623]

Re: Tight shifting from neutral to forward or reverse, 1979 OMC 120

well, did not get a chance to pull the boat out yet. Howard, did you happen to find a part number for what I would be looking for?

 

[anderso8623]

Re: Tight shifting from neutral to forward or reverse, 1979 OMC 120

The lower gear oil seems to be fine, no milky look. What I noticed, after getting the engine warm, the RPMs spike to 2000. I started to pay close attention, when I was idling out, the shifting seemed fine and the RPMs where at 7-900 in gear. On the way in, 2000. I flew into my slip and waited till the next day to test. When I started the motor, it stayed at 1100 in neutral. As soon as the temp got to about 150, the rpms slowly increased to 2000.

I can only assume that the RPMs are not helping my difficult shifting. Is this so? Why would my RPMs spike as the temp went up?

 

[Boomyal]

Re: Tight shifting from neutral to forward or reverse, 1979 OMC 120

.....I can only assume that the RPMs are not helping my difficult shifting. Is this so? Why would my RPMs spike as the temp went up?

Most definitely on the rpm's. IMHO, it sounds like you have a carburetor/vacuum leak issue. I am always having to fiddle with my Holley 4160 to keep the idle down to a decent shifting RPM. If it gets over 800, which is already too high, I cannot pull it into gear. Back to the idle screw, dial it down and it slides right into gear with no effort.

 

[anderso8623]

Re: Tight shifting from neutral to forward or reverse, 1979 OMC 120

Thanks boomyal! This is where I sit. I have adjusted the idle screw so many time I lost count. And that darn stop never seems to sit in the right position. I get it to idle at about 1100, anything below it dies out. I have cleaned the carbs and replaced the gaskets. However, my kit did not come with a manifold gasket. The current gasket was about a quarter inch thick so I figured if I wrenched it down tight, it would seal. I plan to replace as soon as it comes in the mail.

Could this be the reason for the rough idle and stalling below 1100? Would a complete carb replace be considered if it does not solve the issue?

 

[Boomyal]

Re: Tight shifting from neutral to forward or reverse, 1979 OMC 120

As you describe it, it is one of symptoms of a vacuum leak. Small leak at low RPM will cause an elevated and erratic idle but not be an issue once the main fuel circuits kick in at higher RPM. BUT it could be the carb as well. That base gasket does not sound right, especially if it is in any degree spongy. When you replace it, take a straight edge to the bottom of the carb and make sure it is not warped.

In the meantime, while the engine is idling, take an unlit propane torch, open it a bit and run it all around the base of the carb and around anywhere else where there could conceivably be a leak. If there is one, the engine will speed up and smooth out as the propane hits the cylinders.

 

[anderso8623]

Re: Tight shifting from neutral to forward or reverse, 1979 OMC 120

This is where I stand; I have adjusted the idle screw so many times I have lost count. I completely cleaned out the carbs and the only gasket I did not replace was the intake manifold gasket. Only because it did not come with my kit. I ordered one and am going to replace it to see if it works.

If this does not fix the problem, I am considering a brand new carb. Would this be advisable? If so, do you have any suggestions or part numbers? I dont want to get one and have it not fit and the OEM is obsolete.

 

[anderso8623]

Re: Tight shifting from neutral to forward or reverse, 1979 OMC 120

sorry for the double post. I did not see my original post. disregard the last one.

 

[anderso8623]

Re: Tight shifting from neutral to forward or reverse, 1979 OMC 120

Well...no vacuum leaks...until I striped one of the bolts due to lack of exposed threads. The manifold gasket seems to be ok. It is thick but not spongy. When I originally tried the leak test, I used starter fluid as that was all I had. No increase in the rpm. However it did bog down a little... I dont know if this means the same thing. Then I striped the bolt that holds the carb down...luckily it was a removable bolt. Now all I need is a new nut and bolt. However, now that the carb is missing a nut, I get the rpm spike when I spray starter fluid.

I am very close to buying a brand new carb, do you have recommendations?

Jason