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1988 45 hp Mariner, bogging issue.

Brabz1973

Brabz1973

New member
Hi Everyone,
So last fall I bought a 1988 45 hp Mariner at a dealership that someone had traded in for a new outboard.
I've been busy refurbishing my aluminum boat so I'm finally getting it out on the water now.
Took it out for a spin for the first time and found out it was running on 2 out of 4 cylinders. Found out that one carb was plugged up. So I cleaned both carbs out and put new fuel lines.
Engine fires up real nice and runs good.
Took it out for another spin on the water, motor runs good in neutral, but when in forward gear and giving her the gas she starts to bog down and seems to be running on a few cylinders. Seems to be happening underload.

Any thoughts or guidance would be greatly appreciated.
Thanks
 
Have you checked for spark? If no spark try switching the coils around. if the problem follows the coil its a bad coil
 
Can you eventually get it to plane off? If yes, try adding another 1/4 turn OUT (CCW) on the idle mixture screws from your best idle setting.

Jeff
 
Ya I checked for spark. That was the first thing I did. It has good spark on all 4 cylinders.
This is running it at home with muffs on. I'm wondering if underload on the water may be a different story? Is it possible to loose spark underload trying to plane out?
 
O--kay. Now we're getting somewhere.

Here's what to do: With the boat on the trailer, or tied to a dock, warm the motor thoroughly and put it in gear, running as slow as you can without it stalling out. Next, adjust the idle mixture screws on the carbs, taking it nice and slow as you make the adjustments (so the motor levels out at that setting). When you've gotten the best setting you can--she's idling as fast as the adjustments will allow and smoothly--then add 1/4 turn out (CCW) on each screw. Take her for a run and, if she still bogs, add another 1/4 turn out.

Now, is this doesn't cure the problem, you have either too much prop for the boat, improper timing (need to check it), and some other factor.

Jeff
 
Thanks Jeff,
I will give this a try when I get a chance.

Just to be clear on your instructions. You're saying to adjust Idle mixture screws to the best setting, then add a 1/4 turn out on the same screws?

Thanks,
Mike

Oh forgot to mention the prop is a 13 pitch (btw).
 
Last edited:
Thanks, Jeff,
I adjusted the Idle mixture screws as per your instructions, Finally had a chance to take her out for a rip on the water, now I can get her to plane out then shortly after she seems to be starving for fuel and bogs down, Runs well at trolling speed. My next move is to replace the fuel line from fuel tank to the fuel pump an get a fuel pump kit.
 
Don't forget to replace the bulb--I've had a check valve in one lock up and stall the motor similar to yours.

Jeff
 
Jeff,
Finally got a chance to change all fuel.lines and bulb. Installed a new diaphragm kit in the fuel pump. Adjusted the idle mixing screws as per your instructions. Got her running mint on the trailer in a barrel.

Just need to take her for a rip on the water and see if that cured the problem.
Probably be doing that next week sometime. I'll keep you posted for sure.
Thanks
 
Well, I took her out on the water and I am happy to say the motor runs great.
Thank you very much Jeff for your guidance. Very much appreciated.
 
Hey guys I have an 88 45hp mariner and have the same issue. I changed all the fuel lines, new tank, new bulb, plugs, wires, water pump, fuel pump. Did a compression test and only 20psi all around. I dont know what to besides scrap it
 
racerone said:
Repeat the test with a good gauge.
Click to expand...



I will try. When we were doing the compression test it wouldnt get no higher than 22psi. Then we took the plug out and squirted a little oil behind it to see if the gauge was faulty or not and then compression went up to 120psi and gradually went down to 20psi.
 
Hello Captains. I have a 1998 Mercury 250HP EFI that boggs at mid throttle. It starts and idles well. Once I throttle it up at about 5-10 knots it begins to bogg. If I keep the throttle at nearly full power it boggs for a very long time (5 mins or more) chugging along, and then kicks in and plains off and runs smooth. Once I throttle it back to mid speed it begins to bogg until I return to idle. I already changed the plugs, water/gas separator and gas filter. Any advice?
 
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