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Thread: 1989 Mercury 80hp 3 cyl
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07-14-2022, 08:36 PM #15000 RPM
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1989 Mercury 80hp 3 cyl
This motor looks almost like new. It also starts cold and runs great, but then after is has warmed up a while it starts to lose power and stalls out. It's easy to start again at this point but has no power and stalls out especially if you try to accelerate. Try another day and it is fine again, then the cycle repeats. I was pretty thorough making sure the fuel system from tank to carbs is healthy. I'm thinking something like the switch box or coils warm up and then start to faulter. Any advice?
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07-14-2022, 09:20 PM #2
If the switch box is original or very old, it would be good to replace it. You are looking at about 150 or $175 for a good Sierra brand. Also double check the pulse fuel pump and float levels in the carburetors.
1990 Shadow bass boat w/ 2.4 200 Merc. Totally resto'd boat and love it!
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07-15-2022, 06:11 AM #35000 RPM
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08-01-2022, 04:31 PM #45000 RPM
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Replaced the switchbox and fuel pump, also verified the float level on one of the carbs. No dice. Still runs good for a while then I need to keep pumping the ball, and this is sticking with an external tank that I know works. Guess I better check the floats on the other carbs.
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08-05-2022, 03:29 PM #55000 RPM
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Stator, buy a Mercury stator, stay away from after market ignition parts.
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08-06-2022, 07:15 AM #6
Check compression.
RockTeam Junk
No sparkling wiggles in here, only dump truck grinches.
"Screamin Heathen"
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08-07-2022, 08:48 PM #75000 RPM
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08-08-2022, 03:41 PM #85000 RPM
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Tried another set of carbs. Runs the same. Runs for a while then seems to starve of fuel and pumping the ball brings it back. Using good external tank and new fuel pump.
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08-08-2022, 03:44 PM #95000 RPM
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08-08-2022, 04:40 PM #10Member
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could be a bad bulb had it happen before on a omc v4 walmart stuff did not supply enought fuel try mercury bullb
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08-08-2022, 06:52 PM #115000 RPM
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Since it runs when you squeeze the bulb and you have tried a known good fuel supply you may want to check the reed valves. I'm thinking with a broken reed the crankcase pressure needed to drive the fuel pump may not be there. You are correct the fuel pump runs off #2 cylinder.
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08-09-2022, 12:30 PM #125000 RPM
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08-09-2022, 12:33 PM #135000 RPM
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08-11-2022, 06:39 AM #145000 RPM
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So I put a pressure/vacuum gauge at the pulse entry into the fuel pump, and also at the output of the pump. While running, the pulse entry cycled between roughly 5psi and -12psi. This seemed normal to me. On the output end there was 0 (zero) pressure, unless I pumped the ball, then I got around 2psi momentarily. Now this is a brand new fuel pump, not just a kit rebuild. So I took the original fuel pump and applied a rebuild kit, and output pressure is now roughly 4-6psi. The engine seems to operate normally now on all three of the fuel tanks I was testing with. All this testing was on the trailer, so now I need to take it to the lake.
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08-15-2022, 11:42 AM #155000 RPM
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Is this a Mercury fuel pump or aftermarket? I would only trust a Mercury fuel pump.
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