Just bought a 21 ft CC starcraft with a 120 evinrude outboard. I've had it out only three times and each time I work on it it sems to get a little better, but when I am at a high throttle it chugs and bogs down. Med -- Low are OK. Once you back it down and let it catch up it's fine. I have changed the fuel filter and taken the gas tank out drained and cleaned it. Bad plugs or wires? Also Eastern Marine told me that any outboard over 100HP needs to have 3/8 fuel line. I think I have 5/16ths. Is 1/16 of a difference that much different. Also Am I starving the outboard? I plan on changing plugs and fuel line and adding a water sep. on Mon. Any help would be great
Welcome aboard... Yes a 1/16 can make a difference... I've also seen build up in fuel lines even new ones, of stuff that can restrict flow. Yes it sounds like she's not getting the fuel on the high end. It happens in all kinds of engines. even big diesels. I had an issue with one of mine. Kept thinking it was fuel filter and would change when partly dirty. The other engine runs just fine even when very dirty. Then ine day I noticed that a hose clamp to hold the line in one of many places spilled over the "nipple and was squishing the hose. That much was enough to suck the rpm down by a lot.
In addition to DeepC's suggestion, I would like to add that you might want to run some fuel system cleaner in your gas. I use yamaha's Ring Free or mercury's Quickleen. They really work! I like the Ring Free the best- it controls sludge in the fuel tank, cleans sensors and fuel components and removes/prevents carbon build up!
johnebquick Hope you get the fuel line replaced and give us a report on the flatties. Nice to see you signed up on SFC. That Starcraft is looking good with all your hard work you have put into it. The first boat I fished on was a 18' split window starcraft with a 88 merc... In Del Bay catching tide runners, big tide runners(sea trout) with my pop.
with the higher rpm-it's usually a fuel problem...here's a way to narrow it down...you need a remote tank-plug the remote tank into the fuel ball...run the rig-see if the problem's there....if the problem's gone,you're problem is fuel delivery to the engine...you may have a small air leak into a fuel line-the pick up in the tank may have a problem...gotta check it out...
if the problem is still there,it's on the engine side...run the engine at the high rpm's when it starts to load up,hit the choke,if it clears up the problem's in the carb's...
it's all about diagnosis-not throwing parts....
I changed all fuel lines, replaced quick disconnect, prime ball and all hose clamps. Also changed spark plugs, added a water sep and added some Evinrude carbon cuard. Took it out again and still had problems. When I got back home it started right up. Ran at 2800--3200rpms for about 10 min with no problems. I did notice when I took it out that it didn't have the power it had before. I also noticed when I got back to the house that after changing plugs I left one wire off one of the plugs. So now did I fix the problem and it was the wire off the plug that caused this to happen the last time or is the problem still there and I was only running on 3 cyl? Would only running on 3 cyl also make this happen or am I back to the drawing board?
Running a cylider short will not give you an accurate assessment of what the engine is doing. If the plug wire is replaced and the starve is still occuring then I guess the next place to look would be at the fuel pump... I have in the past tested for this by having someone squeeze the promer ball as I throttle up. If she doesn't puke then the pump could be at question...
I had a problem with the same syptoms as yours. I would run the boat and everything was fine. When running full throttle, she would die?? Did everything you did to no avail. Well, I found that the next time the engine died, the fuel bulb had no prime?? Prime it and she started right up. Ended up having a small corrosion hole in the pick-up tube. Dropped a new tube in the old one, and it's been 6 years with no problem. Good Luck.
Al/Muddybottomblues
I will try the fuel pickup next. Some one else also sugested that. Also Jaws I tried Your sugestion when running at WOT ,and it starts to chug, Throw the choke on but it still stalled. Makes me think there is a small air leak or a coil going bad.
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Thanks: From John
