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Honda 75 carbed help needed

J

JackB1

Member
I have a 1996 carbed 75 Honda. It looks new and I keep it as good as I can. Did have an issue with ethanol last year and had carbs rebuilt, tank pumped clean and now use regular gas and run a 10 micron filter. The motor was running the best it ever has......until today. Was out on the river when she idled down on her own, ran rough and almost stalled. My first thought was fuel because of the previous issue. Had wife hold onto dock while I unscrewed filter and emptied into container. Fuel looked clear and fine. Was able to get started and headed back to dock. Got her up on plane but at wide open throttle would only do 24mph [normally 50]. Once in a while she would surge to wide open and run fine for a few seconds then cut back down again. I could tell she was running rough like on 3 cylinders instead of 4.

Back home I first checked the plugs. There was one that was not snapped on tight but did not make any difference in running when I snapped it in fully. I pulled all plugs and they looked fine. I then pulled plugs off one at a time with engine running. For some reason the bottom plug caused engine to stall when others did not. Not sure why.

Then I drained each carb into a glass jar thinking some crap got into carbs from the line between filtyer and engine. All fuel was clear. There was one strange thing. I started at the bottom carb and worked up. When I got to the top carb there was no fuel to drain. I don't ever remember that happening before. Is it possible one of the fuel pumps is to blame? It looks like one [there are 2] pump handles 2 carbs. Would appreciate any suggestions from those with a pay grade higher than mine before it goes to the shop.
 
You have done a lot of good checks...


Sounds like it could be a fuel pump...or you could be sucking air through a loose fitting or hose.

Keep in mind...you have not checked compression...so you do not know it something happened to the engine internally.

Check all your fittings for tightness

Check your fuel filter on the engine....has it been changed lately?

Easiest thing to try is have your wife squeeze the fuel bulb and try to keep it hard when the engine is faultering. Doing this will keep the carbs full of fuel, just like a good fuel pump is supposed to.

If one of the fuel pumps have a ruptured diaphram and is putting fuel into the crankcase, the oil level will have increased and will probably smell like fuel. So...check your oil.

When you pulled the plugs wires off of the spark plugs....did you hear the clicking(arcing) of the spark if you hold the wire near the spark plug? On all cylinders?

Lastly, make sure you are using NGK spark plugs DR7EA.

If all that tests out ok, then see if you can rig up a 6 gallon tank with different fuel and try using it as a test.

Again...if you have good compression and spark (with the proper timing), then you are left with a fuel issue.

Mike
 
Well, I sucked it up and took it to mechanic today. He called and said that I needed a new coil. Could not find it locally so had to order over internet. I did ask why there was no fuel in the top carb when I drained them but he basically said, one thing at a time. I find it hard to believe that two things happened simultaneously so am hoping he is right on his diagnosis. Coil was $104. I am kicking myself for not trying to squeeze bulb when still out on the water. I do think that I heard the clicking when pulling the wires on all cylinders. I do use NGK plugs and will check the oil when i have a chance. Coil will not arrive for a couple of days and will report back when it is installed.
 
Make sure you get the old coil. I have the same feeling as you. It was probably ok unless he knew how to test it. I can not tell you how many times I have gotten calls from other (non Honda) dealers and even a Coast Guard Mechanic who swore they had no spark...and the coils were bad. The coil fires two spark plugs at the same time. If you do not have both leads to the coil connected during the test, it will look like it is bad.

In any case, he is the one looking at it and it is easy to second guess...so I should keep my mouth shut.

You motor is one of the original 75 HP's that Honda made, so just about anything could be going on.

Keep us posted.

Mike
 
OK, here is the outcome. I explained the coil procedure to my mechanic who said he was aware of the issue and uses a homemade setup to do the testing. Coil was replaced and the engine is running fine. Could it have been a stuck needle valve and I just ended up paying $104 for an un needed coil. I guess that I will never know. I do appreciate the help from the forum and hondadude. Gives us a leg up when having these issues.
 
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