need help with cleaning engine

[garzaglass]

1979 75hp evinrude
the last time i was out last season the engine seemed like it was not getting enough gas the more throttle i gave it. i found out later about how i should have been running the gas out of it every time i was done for the day because of the oil build up. i had run the boat several times without doing this so i hope that its just an oil build up problem. from reading the threads i have seen some things i should do to fix this problem (clean carbs, float bowls, needles ect...) the problem is i dont know where or how to do this. I am new to mechanical work on boat engines. if there is a thread with pictures that show what these things look like that would be a great help. i know how these things work and what they are for i just need a starting place. also the engine has been sitting since aug 07 with gas in it and 10 gallons of gas in my gas tank (mixed). can i still use this gas if i add a additive to it or will i have to throw it out and start over?

thanks for all the help.

 

[jtexas]

Re: need help with cleaning engine

your carbs are remarkably simple devices compared to, say, automotive carbs...three fixed jets, no needle valves. but I wouldn't try it without a repair manual. a factory shop manual is a great investment, will pay for itself many times over. try kencook.com or marineengine.com . iboats has the seloc manual - it has some good information but covers so many models it's kinda confusing in places. carb kits about $12 apiece on iboats.

meanwhile, don't run it like it is - any cylinders starving for fuel are also not getting oil.

You'll also want to do a compression test and spark test.

It's not so much oil building up as evaporating gasoline leaves varnish. A lot of people been running 'em dry for years and never had a problem. Yet. Not such a good idea because the top cylinder empties first and runs without lubrication while the other two run dry. A bit more trouble, but it's better to drain the carb bowls. Take the airbox off and remove the screw plug front and center at the bottom of each carb bowl.

sorry to say, last summers gas will have to be drained. there are additives to keep gas fresh (stabil, seafoam), but nothing can make bad gas into good gas. it can be used a little at a time in your lawn mower or truck.

 

[garzaglass]

Re: need help with cleaning engine

is there any threads that have pics of what the things your talking about look like? ex: "Take the airbox off and remove the screw plug front and center at the bottom of each carb bowl." ive never seen these things so i dont know where to start.

 

[JJags3]

Re: need help with cleaning engine

You absolutely need to buy a manual, everything you have asked is in there. I like Seloc's.

 

[Silvertip]

Re: need help with cleaning engine

The very best manuals are the factory service manuals and be sure to get one specific to your engine. Visit your local library. They often have these manuals. While they may not have one for your specific engine, carbureted outboards are fairly generic. Carbs toward the front, flywheel on top, heads point to the rear. Try e-bay for manuals as well. Understand that you need a "service manual" not an operators manual.

 

[cmuman]

Re: need help with cleaning engine

Don't run the boat any more until you fix the gas issue. It will fry your piston. I agree that boat carbs are way easier than automobile carbs. Compression test will also tell you a lot.

 

[jtexas]

Re: need help with cleaning engine

If I get a chance I'll try to take some pics tomorrow.

You can view your engine diagrams online at www.evinrude.com click on Parts & Accessories / Electronic Parts Catalogue then select your year/hp/model #, but it's no substitute for the manual.

 

[jtexas]

Re: need help with cleaning engine

 

[garzaglass]

Re: need help with cleaning engine

thanks jtexas, thats exactly what i needed! i had a good idea about where to start but just wanted to make sure. so all i need to do is clean out every orafice i can see in the carb with carb cleaner and also take the bowl off and clean it out? then put it back together using a carb kit? from what i have seen the carb kits have new gaskets and seals. is there anything else i need to replace while doing this? also i will need to know how a compression test is done. from what i have seen it looks like a device is used in the spark plug hole. is this correct? and if so where would i find such a device and what kind of compression am I looking for? i think im going to order the seloc online manual. it looks to be the easiest. for some reason i cant figure out how to find a carb kit for my specific motor on iboats. i must be missing a simple link! please let me know if there is any other maintenance i should be doing after letting my motor sit all winter with old gas in it. thanks for your help.

 

[jtexas]

Re: need help with cleaning engine

One rod links the 3 throttle butterflies, one rod each linking the top & bottom chokes to the middle. Linkages just pop out of the plastic retainers. Two nuts holding each carb to the intake.
Four screws to remove the bowl.
Three screw plugs to remove, a jet behind each one. The hi-speed jet is behind the drain screw, the idle jet is behind the screw at the top on the front of the carb body, and the off-idle screw is on top, starboard side, sticking out at a 45? angle.

There's a "special tool" you need to remove the jets, but you can fabricate it from a screwdriver and belt sander or dremel. read about it here: http://forums.iboats.com/showthread.php?t=220506&highlight=special+tool

Disassemble, (don't mix the parts), soak overnight in carb cleaner, blow out the orfices with compressed air (or aerosol carb cleaner), put it back together with the kit. Don't forget the float valve and seat. The new float hinge pin might not fit your carb too well, just use the old one no problem. Best to keep the plastic parts out of the cleaner. The kits have instructions.

Find your motor on this chart:
http://www.iboats.com/Evinrude_Carb...5715371--**********.495049055--view_id.269096

I've always used the sierra kits, no problems. Comes with or without a new float. You probably won't need the float.

The manual will walk you through the link & sync, but you shouldn't have to worry about resetting the timing.

Compression gauge, any car parts store. Start the engine & let it idle up to operating temp. Disable spark by pulling the emergency lanyard (your motor didn't come factory equipped with one of these), or remove all the plugs and ground the leads to the block with jumper wires. Screw the gauge into the top hole and turn the engine over for a few seconds. Repeat a couple times. Note the reading and reset the gauge for the next hole. Difference between cylinders is more important than the actual result. The lowest should be within 5 or 7% of the highest. Expect 120's, but anything over 100 would be good.