I bought a used 75hp Evinrude outboard motor from the 1970's. Model 75543B. It came on a Starcraft Jupiter V boat 16ft long. The boat has a top speed of about 6-7mph (11kph). I'm not sure what's wrong, but I think maybe it's running on only 2 cylinders instead of the full 3. I think maybe I need to change a spark plug wire. How long should the wire be from the coil to the cap?
If the problem is not that one cylinder is not firing, what are other possibilities about this problem? The engine does not seem to rev as high as it could. It just seems to go at a slow cruise. It starts well, but only seems to reach 1/2 to 2/3 speed, and doesn't plane out the boat.
Make (of engine): Evinrude
Model (of engine): 75543b
hello. i have changed the format of the screen from chat to Q@A . it will allow you to follow troubleshooting procedures when you have the time. there is NO EXTRA CHARGE.Before you spend money on plug wires, the ignition test thats coming up could show you the spark is strongYour outboard is a premix engine, that means the carburetors are responsible for delivering the oil to your crank bearing and components. If this engine has been sitting for a extended period of time. The carburetors could be stopped up with varnishwhat it takes to make any engine run is compression, spark, and fuel.. compression is easy, you can pick up a compression gauge at any automotive parts store for less than $50. compression test do more than tell you if the engine is good it can tell you how clean the engine is. The fuel pump runs off engine compression and crankcase vacuum for examplecarbon build up on the piston rings will cause a issue called sticky rings. it can be solved by just running de-carbonizer through your engine. your outboard needs to be a minimum of 100 psi and all cylinders need to equal each other within 10 psi.so step 1 do compression checkStep 2 spark gap test. A spark gap tester allows us to test the strength of the ignition system by making the spark jump up to a 1/2 inch. The spark gap tester cane be purchased at any parts store. The following address will give you a image example. http://www.thetoolwarehouse.net/p-7200-thexton-404.aspx
I think the boat has not been used for a couple years at most, but not unused for a really long time. I bought STP Complete Fuel System Cleaner to put in the gas tank.
So, first I need to buy a compression gauge and test the engine compression? What do I need to do if the compression is low? Should I run at tank of gas with STP through the engine first, just to eliminate the sticky ring possibility?
Everything we will do to your engine, will be decided after we do the troubleshooting. That way we are not wasting your money and time on something you may not need.Those two tools listed, you will always need as a 2 stroke outboard owner.After you complete the troubleshoot test. Contact me when ever you can. There is no rushThank you
Thank you. How can I contact you again? Do I need to logon to this website? How do I find and contact you?
It's easy. Just come back to this website and follow the reply link. And don't worry about the time, I just solved a persons boat problem over a five day conversation. So please take your time. Thank you
Relist: OtherFollowing up on your suggestions...
To follow up on your advice...I bought a compression tester and tested the outboard motor. All three cylinders are about 120-125 psi, so I think the compression is ok.
In the process of testing the compression, found the problem. When I took the cover off the outboard and really looked at the motor, I noticed some silicon sealer around the base of one spark plug wire, where it attaches to the coil. I peeled the silicon away and the wire seemed a little bit loose. When I pulled it out of the coil socket, there was little resistance, and there was a ragged little bunch of wires hanging out the end of the insulation. Even with the little I know about motors, I still thought that didn't seem right, like maybe there wasn't a good contact. I pulled the other end of the wire out of the spark plug cap, and the wires were cut even with the insulation. I went to a boat shop and bought some new spark plug wire. The instructions for installing a new spark plug wire suggested to me that the old wire was installed backwards by the previous owner. The silicon seal suggested that maybe the previous owner was having trouble with that particular cylinder/wire/coil. According to the instructions, the clean-cut end should have been screwed down onto the threaded little post in the coil socket, and the ragged end should have gone into the spark plug cap, where the loose bundle of wires would have ensured good contact. So...I cut the new wire to the same length as the old one, and installed the new wire according to the instructions. As extra insurance, I also put in new spark plugs. The old NGK plugs were a recommended alternative to the specified Champion plugs (I found the specs on the internet), but according to the sales guy at NAPA auto parts, the particular NGK plugs in the motor were a little hotter-burning than the originally-specified Champion plugs. I bought the right Champion plugs and installed them. When I fired up the outboard in my driveway (with water hose attached), the motor started instantly and sounded smoother and noticeably more quiet than before. I took the boat out on the water and it now revs higher and tops out at 47.5km/h, which is WAY better than the 11km/h it did before, and easily planes out the boat. It also trolls smoothly at the slowest speed I can make it do, without stalling/quiting. So....I think the problem is solved.
So...thank you very much for your first step of advice. I now know how to do a compression test, and have learned a bit more about how outboards work.
Is there anything else you think I could/should do with this outboard? Is the compression of 120-125psi good? Should I do anything to improve the compression, and if so, what should I do? Any other advice about how to properly put the outboard away for the winter, or upgrades to improve fuel efficiency, whatever, would be appreciated.
Thanks very much Scott!
Hello Jim Great job on the troubleshooting. Your compression is with in spec. The main thing you will always want to do is keep all your fluids fresh. 1) Fuel = all fuels Whether it is ethanols based or not has a shelf life. Here in Texas fuels are up to 10 % ethanols and it has a shelf life of thirty days. If you are unable to drive your boat as often as you drive your automobile, then you must run the engine until all the fuel is used up in your fuel tank . Then from now on drive you boat every thirty days with just enough fuel to we're you run dry. The point I'm making is to cycle your fuel. Never leave fuel in your engines carburetors or fuel tank that is more Than thirty days old. The alcohols content will damage all rubber and plastic fuel components. With all per-mixed engines run ratio is 50 to 12) gear case or lower unit oil. Both names refer to the housing were the propeller is turning. There is gear oil in this unit. It is always below the water. It is important that no water gets in and you oil is clean.Thank you, XXXXX XXXXX time on the water.
Over 18 years experience in the water sports repair industry.