Evinrude 75 - Please Help

[SFAgent]

1983 E75TRLCTE idles perfectly but when shifted into gear (forward or reverse) almost immediately bogs down and stalls. Previous owner had not used the motor for several years. I am new to powerboating and would appreciate any suggestions on how to improve the performance of this motor. What is the best way to tune up this motor??

 

[jtexas]

Re: Evinrude 75 - Please Help

welcome to iboats!

If you're the least bit handy (and you better be if you want to own a boat), you can maintain this motor yourself with just the basic tools and a good service manual. I highly recommend the factory manual.

Basic Troubleshooting 101:

1. Compression test. look for compression to be about the same on all 3 (within 5 or 7%).
2. Spark test. get an inline spark tester (couple bucks at autozone), set the gap for 7/16", clip it to the engine block, attach the plug leads (one at a time) and look for a strong blue spark while cranking. If it can't jump a half-inch gap in the open air without a spark plug, it's a good indication that it's not firing in the heat & compression of the combustion chamber.

Report your results.

3. spark plugs should be champion QL77JC4 gapped at .030, in good condition. I have nothing against other plug makers, but this motor will run it's best with that plug -- trust me on this.
4. make sure the fuel is fresh 87 octane gasoline mixed with TCW3 certified oil in a 50:1 ratio.
5. make sure the tank is free of water and debris.
6. make sure the tank vent is open and clear.
7. make sure the fuel line holds pressure.

if all the above checks out:
8. rebuild the carbs. Don't be intimidated, these carbs are really quite simple devices. You can do it. Order 3 carb kits from iboats (without floats). Matter of fact, on an engine that sat for 3 years, rebuild the carbs now anyway, just on general principle (that's my opinion).

Go over to the Engine FAQ section of iboats and read the carb rebuild thread.

Go ahead & order your manual now, too. It will pay for itself many times over.

If you don't know when the water pump was last serviced, or if it's been more than two years, go ahead & plan on replacing the water pump impeller soon as you can get around to it. Actually, same advice here as the carb -- after sitting 3 years unused, replace the impeller sooner rather than later. Wouldn't want bits of dry rotted impeller clogging things up.

You're gonna love that motor.

 

[SFAgent]

Re: Evinrude 75 - Please Help

Thank you very much for your advice and direction, it is greatly appreciated and I will report my findings for compression once I have checked them. On another note, I have read in several other posts that in order to setup a tachometer I need to find a grey wire that would be attached to the terminal pole on the motor, however I have not found any grey wires anywhere on the engine. If I send you a photo of my motor, could you please advise as to where I need to attach a wire for a tach and what type/setting I will need for this particular motor to read correctly? Much thanks in advance.

 

[jtexas]

Re: Evinrude 75 - Please Help

if you have the OMC control box, look right beneath the throttle tension control knob, which is just below the keyswitch. Under that rubber boot is a three-hole socket, that accepts a plug-n-play tachometer wiring harness -- I got my harness off the shelf at basspro, but you can probably find it at most other marine stores. Three wires -- purple (switched accessory power) goes to the IGN terminal on back of the tach, black (engine block ground) to GND and gray to SND. Wire the LT terminal to your helm light switch. Set the tach pole setting to "12p".

If you can't or don't want to find the harness, you can open the control box and find those three wires in there.

 

[SFAgent]

Re: Evinrude 75 - Please Help

OK now I am completely and utterly confused.... I have checked spark in all 3 cylinders and have good spark in all, compression in all three are good. I thought that before I spent the time and money on the carb rebuild kits that I would run some seafoam through the motor to clean up any gum issues that would have been present after three years of sitting unused. Now the motor idles better and will shift into forward and I can give it throttle on muffs (I know you aren't supposed to do this but I was trying to prove a point to my father in law). Motor ran like a dream on muffs, took it out on the river the other day, same problem gave it throttle and it bogged down immediately. My first impression was that since it didn't do that on muffs, would the pressure of the water in the river make a difference in the motor performance?? My immediate thought was that it was probably the fuel pump since the carbs were cleaned out with seafoam and the carb gaskets seem to be in relatively good condition. Any help would be appreciate very much as I am ready to throw in the towel.

 

[jtexas]

Re: Evinrude 75 - Please Help

Well, you got it all the way to the 2-yard-line and stepped out of bounds. C'mon, push it on into the end zone!

Running on the muffs, the motor is completely unloaded. It'll run all day on 2 cylinders and sound happy doing it, then crap out when you put a load on it.

This is really not the least bit surprising. Remember how I said "rebuild the carbs now anyway, just on general principle"?

Don't be discouraged, though, we all learned the hard way...the carbs can not be cleaned without disassembly. Seafoam is great stuff, I add it to my fuel, but the fact is, anything strong enough to clean your carburetors will burn a 2-stroke engine up if you try to run it in the gas tank.

So, the carbs have not been cleaned, and regardless of how they may seem, the gaskets may or may not be in good condition -- you just can't eyeball 'em and tell.

Very unlikely to be the fuel pump...see #7 above, if the line's holding pressure, the pump's ok. If it's not holding pressure the pump is still probably ok. If there's fuel leaking out of that hole on the backside of the pump housing, the fuel pump needs a rebuild.

Don't be intimidated, these carbs are amazingly simple devices -- you'll be very happy with the result. I promise.

[btw, revving it up on the muffs, very risky. search this forum for "thermal runaway"]

 

[Daviet]

Re: Evinrude 75 - Please Help

When you overhauled your carbs did you remove the core plugs on the top of the carbs and clean the low speed passages? Do your carbs have adjustable low speed jets, are they set properly?