Joe Todaro
New member
Hoping someone can give me some good advice because I am going nuts with this engine. Recently purchased a 1981 Mako 170 with a 1985 Johnson 120HP. Boat has been running on a 6 gallon external tank for the past 5 years by the previous as he told me there was a problem with the internal fuel tank. Boat ran fine on the external but I decided to make the investment and do the following:
- Put brand new 24 gallon internal tank in
- Did some re-wiring under the center console (wires were a mess plus light and bilge switch did not work. Put a new rocker switch panel on...everything now works)
- Changed all 4 spark plugs
- Installed a water separator (the boat did not have one installed nor could I find a fuel filter anywhere)
After all of the above was completed I had a problem starting the engine...before the engine started on a dime, now I have to give it throttle to get it started. Engine will start and stall consistently.
Had a mechanic stop by and he said I was have a problem with the 2 lower carburetor's (one on each side). I took the carbs apart and cleaned. 2 of them (uppers) were a little dirty. Put them back together and it was a little better but still kept stalling. Same mechanic did a compression test and 3 cylinders were at 125 and the 4th at 120 (sounds good). He told me to put the boat in the water and see how it runs. Did that and the engine kept stalling. Kept trying and got it running. It would run fine for about a minute and then bog down then pick up again and then bog down again and then eventually stall. I kept hearing the RPM's change on its own, plus I was blowing a lot of smoke. Noticed that my oil reservoir which was almost full was down to about a 1/4 tank..hence the VRO was giving too much oil. I bypassed the VRO and did a direct fuel/oil mixture into the new tank. A little better but still stalling and changing in RPM's on its own.
Last night I disconnected the fuel line from the fuel pump to the carburetor to see the flow of gas. This is I guess where my question is...what should the flow of gas look like??? When I cranked the engine fuel shot out in a steady stream and then reduced a little...then shot out in a stream again. Is this normal? (I have a video of the fuel pump working but I don't know how to upload it here)
Any other ideas of what can be causing this? It's driving me insane.
- Put brand new 24 gallon internal tank in
- Did some re-wiring under the center console (wires were a mess plus light and bilge switch did not work. Put a new rocker switch panel on...everything now works)
- Changed all 4 spark plugs
- Installed a water separator (the boat did not have one installed nor could I find a fuel filter anywhere)
After all of the above was completed I had a problem starting the engine...before the engine started on a dime, now I have to give it throttle to get it started. Engine will start and stall consistently.
Had a mechanic stop by and he said I was have a problem with the 2 lower carburetor's (one on each side). I took the carbs apart and cleaned. 2 of them (uppers) were a little dirty. Put them back together and it was a little better but still kept stalling. Same mechanic did a compression test and 3 cylinders were at 125 and the 4th at 120 (sounds good). He told me to put the boat in the water and see how it runs. Did that and the engine kept stalling. Kept trying and got it running. It would run fine for about a minute and then bog down then pick up again and then bog down again and then eventually stall. I kept hearing the RPM's change on its own, plus I was blowing a lot of smoke. Noticed that my oil reservoir which was almost full was down to about a 1/4 tank..hence the VRO was giving too much oil. I bypassed the VRO and did a direct fuel/oil mixture into the new tank. A little better but still stalling and changing in RPM's on its own.
Last night I disconnected the fuel line from the fuel pump to the carburetor to see the flow of gas. This is I guess where my question is...what should the flow of gas look like??? When I cranked the engine fuel shot out in a steady stream and then reduced a little...then shot out in a stream again. Is this normal? (I have a video of the fuel pump working but I don't know how to upload it here)
Any other ideas of what can be causing this? It's driving me insane.
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il ratio and making it smoke. Check all of your connections to the fuel tank and make sure all fittings are snug and air tight.