This is going to be a lengthy description, but I have made numerous repairs/fixes and am at my wits end no longer knowing what information is pertinent or not.
Problem:
A4 starts, idles fine, when throttle is increased slightly RPMs increase all the way to up to 4000 RPMs.
Now the lengthy description. I bought a ’79 columbia 8.3…A4 did not run. carburetor was already removed. In getting the engine back in shape I’ve done the following:
1) Checked raw water flow
2) Emptied old gas from fuel tank with pump also got out a lot of sediment from bottom of fuel tank.
3) Replaced impeller (bought from Moyer)
4) Replaced thermostat with single action 160 degree thermostat and (bought from moyer). Engine was running hot at idle…problem fixed.
5) Took apart and resealed mechanical fuel pump after small fuel leak in gasket around housing of manual primer. No more leaking of fuel.
6) Replaced spark plugs. Plugs were Champion replaced with equivalent spark plugs from autolite.
7) Added 15 gallons 92 octane gas to fuel tank
8) Replaced fuel filter/ water separator on fuel line before fuel pump
9) Replaced fuel line (copper tubing running from Fuel Pump to Carb. Fuel Inlet) A4 Manual says 5/16” Outer Diameter couldn’t find 5/16’’ so I used ¼” copper tubing (1/16 smaller) with compression fittings
Now the carb.
1) Bought Moyer Marine Service and overhaul manual
2) Ran step by step through disassembly, cleaning (with Carb cleaner), and assembly in Fuel System section of Moyer manual…carb was already very clean to start with.
3) Bought Tachometer (bought from Moyer) to view what RPMs engine was running
4) Installed carb….started engine…no change. Engine idles great, a little high around 900-1000. I got it down to 800 rpms but it runs a little rough. Give it a little throttle and RPMs scream up to 4000.
5) Removed choke cable and throttle cable…operating everything now straight from levers on carb. Move throttle lever 1/8th inch throttle up RPMs jump to 4000
6) Rpms go so high tachometer breaks first day it was installed!!
7) I know what you’re thinking now…Mixture!!! Just to be sure I removed the carb and disassemble again. I TOLD YOU IT WAS GOING TO BE LONG.
We are not done yet.
8) Removed all jets, needles, gaskets, float assembly, reassembled with new gaskets (Moyer gasket kit)
9) Set all screws as follows according to a Gravely publication on Zenith 68 carbs.
Throttle stop screw - held throttle at stop position, turned throttle stop screw until it touched stop, continued screwing in 1.5 turns
Main Jet – screw in until seat turned back out 2.25 turns (left)
Idle Adjust Needle – screw in until seat turned back out 1 turn
10) Installed carb. still with no throttle cable. Same result! Idles great, starts pretty well with little to no choke (Raises questions! Addressed later.) Move throttle lever 1/8th inch throttle up engine RPMs go high. (no actual RPMs Tachometer is broken). Tried from no throttle to throttle up under load in forward. No Change! Still high RPMs with very little throttle up. Same in reverse. Unscrewed (turned left) main jet needle 1, 2, 3 full turns to lean mixture no change at all. Maybe slightly rougher idle when main jet needle out 3 full turns (5.25 full turns from seat).
11) Remove carb AGAIN. Remove flame arrestor. Plate that is the Choke Valve is bent leaving valve open even when choke lever is closed. Flatten out choke valve plate, reassembled; assured tight fit when choke is in closed position.
12) STAY WITH ME ALMOST DONE… Last thing I can think to check while I have the carb off…Float and float assembly. Took float assembly apart again, checked port, movement of main jet needle, reassembled float….
13) Checked float level height as according to Gravely Zenith 68 publication. “With bowl cover inverted viewed from free end of float the float bodies must be centered and at right angles to the machined surfaces. The float settings is measured from the machined surface (no gasket) of cover to top side of float bodies highest point” dimension should be 1 5/32” plus or minus 3/64”…my float was 1 12/32” Ah Ha THIS must be the problem. Using needle nose pliers and some pretty precise calipers I got the float centered and square at 1 6/32”
14) Carb reassemble, put back on the A4……wait for it……wait for it…..NO Change. Same problem. Idles good. Needs coke to start now. 1/8th inch throttle up RPMs go to the sky.
I’m staring to think it isn’t the carb. I need to be chasing, but don’t know what else to try any ideas at all are helpful. Don’t want to spend $150 on another tach until problem is fixed. More importantly, NO sailing at all this season because of engine trouble. I’m so close I can feel the wind. Please help.
Problem:
A4 starts, idles fine, when throttle is increased slightly RPMs increase all the way to up to 4000 RPMs.
Now the lengthy description. I bought a ’79 columbia 8.3…A4 did not run. carburetor was already removed. In getting the engine back in shape I’ve done the following:
1) Checked raw water flow
2) Emptied old gas from fuel tank with pump also got out a lot of sediment from bottom of fuel tank.
3) Replaced impeller (bought from Moyer)
4) Replaced thermostat with single action 160 degree thermostat and (bought from moyer). Engine was running hot at idle…problem fixed.
5) Took apart and resealed mechanical fuel pump after small fuel leak in gasket around housing of manual primer. No more leaking of fuel.
6) Replaced spark plugs. Plugs were Champion replaced with equivalent spark plugs from autolite.
7) Added 15 gallons 92 octane gas to fuel tank
8) Replaced fuel filter/ water separator on fuel line before fuel pump
9) Replaced fuel line (copper tubing running from Fuel Pump to Carb. Fuel Inlet) A4 Manual says 5/16” Outer Diameter couldn’t find 5/16’’ so I used ¼” copper tubing (1/16 smaller) with compression fittings
Now the carb.
1) Bought Moyer Marine Service and overhaul manual
2) Ran step by step through disassembly, cleaning (with Carb cleaner), and assembly in Fuel System section of Moyer manual…carb was already very clean to start with.
3) Bought Tachometer (bought from Moyer) to view what RPMs engine was running
4) Installed carb….started engine…no change. Engine idles great, a little high around 900-1000. I got it down to 800 rpms but it runs a little rough. Give it a little throttle and RPMs scream up to 4000.
5) Removed choke cable and throttle cable…operating everything now straight from levers on carb. Move throttle lever 1/8th inch throttle up RPMs jump to 4000
6) Rpms go so high tachometer breaks first day it was installed!!
7) I know what you’re thinking now…Mixture!!! Just to be sure I removed the carb and disassemble again. I TOLD YOU IT WAS GOING TO BE LONG.
We are not done yet.
8) Removed all jets, needles, gaskets, float assembly, reassembled with new gaskets (Moyer gasket kit)
9) Set all screws as follows according to a Gravely publication on Zenith 68 carbs.
Throttle stop screw - held throttle at stop position, turned throttle stop screw until it touched stop, continued screwing in 1.5 turns
Main Jet – screw in until seat turned back out 2.25 turns (left)
Idle Adjust Needle – screw in until seat turned back out 1 turn
10) Installed carb. still with no throttle cable. Same result! Idles great, starts pretty well with little to no choke (Raises questions! Addressed later.) Move throttle lever 1/8th inch throttle up engine RPMs go high. (no actual RPMs Tachometer is broken). Tried from no throttle to throttle up under load in forward. No Change! Still high RPMs with very little throttle up. Same in reverse. Unscrewed (turned left) main jet needle 1, 2, 3 full turns to lean mixture no change at all. Maybe slightly rougher idle when main jet needle out 3 full turns (5.25 full turns from seat).
11) Remove carb AGAIN. Remove flame arrestor. Plate that is the Choke Valve is bent leaving valve open even when choke lever is closed. Flatten out choke valve plate, reassembled; assured tight fit when choke is in closed position.
12) STAY WITH ME ALMOST DONE… Last thing I can think to check while I have the carb off…Float and float assembly. Took float assembly apart again, checked port, movement of main jet needle, reassembled float….
13) Checked float level height as according to Gravely Zenith 68 publication. “With bowl cover inverted viewed from free end of float the float bodies must be centered and at right angles to the machined surfaces. The float settings is measured from the machined surface (no gasket) of cover to top side of float bodies highest point” dimension should be 1 5/32” plus or minus 3/64”…my float was 1 12/32” Ah Ha THIS must be the problem. Using needle nose pliers and some pretty precise calipers I got the float centered and square at 1 6/32”
14) Carb reassemble, put back on the A4……wait for it……wait for it…..NO Change. Same problem. Idles good. Needs coke to start now. 1/8th inch throttle up RPMs go to the sky.
I’m staring to think it isn’t the carb. I need to be chasing, but don’t know what else to try any ideas at all are helpful. Don’t want to spend $150 on another tach until problem is fixed. More importantly, NO sailing at all this season because of engine trouble. I’m so close I can feel the wind. Please help.
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