Lo Power under load 4 cyl 120

[crawdatiboats]

I have a 120 in line 4-cylinder 17-foot runabout. The engine runs fine in the drive way, but when I put it in the water and go to take off the engine "bogs down" with no power. I have replaced the point, condenser, Button and Cap. Timing is ok. I took the fire arrester off at the lake and could see fuel spaying into the carburetor. I changed the in line fuel filter and inspected the carburetor filter. I took the top of the carburetor off and it looks clean and no water in the bowl.

 

[wake5150]

Re: Lo Power under load 4 cyl 120

I'm not sure what Year or Carb you have, but typically....<br /><br />Typically IDLE is set with the boat in the water, in gear, with the throttle cable disconnected from the carb. This is quite different than running in the driveway.. <br /><br />I.e. if you set the IDLE at 600rpm in the water, it will probably be 800rpm in the driveway. <br /><br />Conversely if you boat IDLES at 600RPM in the driveway, it will probably IDLE at 450RPM in the water....<br /><br />Point: Set your IDLE with the boat IN the WATER according to your manual and I think you'll be fine.<br /><br />Wake

 

[jeff13601]

Re: Lo Power under load 4 cyl 120

Did you set the dwell on the points? What shape are the plugs and wires in?

 

[crawdatiboats]

Re: Lo Power under load 4 cyl 120

The Boat is a 1974 murcruiser. The carb is a Rochester 4GC. Running at idle speed is not he problem. It runs fine at idle. It is when I go to take off where the engine bogs down.<br /> The Pugs and wire are in good shape. I did not set the Dwell. I did set the point gap at .022 according to the manual.

 

[jeff13601]

Re: Lo Power under load 4 cyl 120

I set my points by gap and it was completely different with a dwell meter. Don has put a lot of links for properly setting the points with a dwell meter. Is the timing advance ok?

 

[Phantom17]

Re: Lo Power under load 4 cyl 120

You mention a "4GC" is this a 2bbl or 4bbl? I too have what I beleive is a GC carb, but a 2bbl. I see an "4MV" in the manual though. I just ordered a rebuild kit over the phone as I have the exact problem you mention. Purrs in the driveway, get about 2800-3100 in the water then it boggs down hard. Worked fine (in and out of the water) until I replaced a plug behind the choke. Let me know if you find your problem. Theres quite a few of us with this problem and everyone says to rebuild the carb. Good luck.-Jeff

 

[crawdatiboats]

Re: Lo Power under load 4 cyl 120

To rebuild the carburetor is the only thing that I have not done. It is a 2-barrel carburetor. What "plug" did you replace behind the choke? Did it fix your problem?

 

[crawdatiboats]

Re: Lo Power under load 4 cyl 120

I was wromg about the carb it is a 2GC and this is a 2 barrel

 

[Phantom17]

Re: Lo Power under load 4 cyl 120

There is a welch plug behind the choke. It looks like a concaved nickel, 5/8 of an inch round. The guy I bought the boat from took a bolt, washer and 2 nuts, made a plug, and glued it in with orange gasket sealer. Boat ran mint, 4800 rpms w/o a problem. Came out of the water faster than I expected. Then I put a real plug there (I wanted the right part there). That's when my problems started. After I put the welch plug in, bang, 3100 max rpm and the motor sounding like it was starving. I made the carb leaner, got nowhere, richer got maybe 100 more rpm, same problem. I am actually going to re-install the manmade welch plug tonight, test it this weekend and see if the problem is gone. If not, new welch plug and re-build carb. You?????<br />-Jeff

 

[Phantom17]

Re: Lo Power under load 4 cyl 120

BTW, still purrs in the driveway, with the real welch plug, problem only occurs on the water.

 

[crawdatiboats]

Re: Lo Power under load 4 cyl 120

Jeff,<br /> I rebuilt it about a year ago and it has been doing fine. I took the carburetor apart tonight and cleaned it with carburetor cleaner and spayed it with compressed air. I did not see anything that looked bad or even dirty for that matter. I will take it to the lake tomorrow and see how it works. <br />On yours do you think that you cold have got some of the orange gasket sealer down into one of the orifices causing your problem? Did the homemade plug mess up your hole for the plug? That carburetor is easy to go though so once you get your rebuild kit and go though it you should be in good shape.

 

[Phantom17]

Re: Lo Power under load 4 cyl 120

The choke is sealed off from the carb so no, I don't think any of the orange stuff got loose. The home made plug was pretty good actually, just didn't want it to be the source of getting stuck out with the kids. I'll put it back in and see what gives, if not rebuild the carb. never done one before so I'm a tad skeptical about not having the right adjustments.

 

[crawdatiboats]

Re: Lo Power under load 4 cyl 120

I picked up a manual from the marina written by "seloc" that has very good step-by-step instructions on how to adjust the carb. It is well worth the $20 investment. It also has good blow-ups diagrams. Another trick that I found if you have never done it before is to use your digital camera and take some reference pictures before you start so that you can refer to if you get stuck. Good luck!

 

[Phantom17]

Re: Lo Power under load 4 cyl 120

Thanks, I'll pick one up. I took the welch plug out today to re-install the home made one, and low and behold, I found a "wad" (like in size and shape of a shotgun shell wad) of gasket stuff inside the choke body in the choke piston channel. I removed it, got a new plug and installed it. Put it all back together and adjusted the choke. (I set it so that it was just closed, but engine wouldn't start. Leaned it up, started, run, started, run etc. See what happens when I get it out on the water.

 

[crawdatiboats]

Re: Lo Power under load 4 cyl 120

the lake and all is well. There must have had something in the Carb.Jeff,Let me know how you make out. Thanks for the help! Mark

 

[Phantom17]

Re: Lo Power under load 4 cyl 120

Hopefully today, if my plans go right!

 

[Phantom17]

Re: Lo Power under load 4 cyl 120

Problem solved. The "wad" of gasket goop was the problem. Got out on the lake, popped the throttle forward and took off. Glad I didn't rebuild the carb etc etc. I'll do that later.