Can't run wide open after fixing regular culprits; HELP!

[kiddynomite]

I have tried searching these symptoms before I posted but can't find the identical topics discussed here, and, I have posted some round about questions the past few days hoping not to take up too much of anyone's time and/or brain cells - but I'm thoroughly stuck.

I have a 1982 Evi 70hp - the last time it was in the water was 5-6 years ago and it ran fine, minus a little hesitation when you dropped the hammer (1 second worth). I have finished rebuilding/painting the boat recently and I put it in for a "sea trial" and it started right up, idled awesome and cruised out of the launch site fine. The problem is when you try and run it wide open - it goes maybe half speed (that's a guess, I have no tach or speedometer).

I had a small leak when I primed the tank tight at the motor that went away after a second or two or it started running. I cleaned the carbs and the bottom two were pretty well gunked up, the ignition system is firing good - the middle plug is a litle wet while the top and bottom tend to be dry(er). The compression is right where the book says it should be and still, the exact same problem. It didn't run any better after we cleaned the carbs - which sealed up nice and fine but a little gas drops down from them when it runs but I can't pin point it.

That's all the information I can think of off the top here, any and all help will be greatly appreciated.

 

[HighTrim]

Re: Can't run wide open after fixing regular culprits; HELP!

This is in the FAQ by Joe, it may help in your problem, after that you may want to read Waking a sleeping engine. You said you checked the compression but maybe check the spark as he explains here. gl

(Compression & Spark Test)
(J. Reeves)

1st - Regardless of what problem one might encounter, always start with the basic troubleshooting procedure. Check the compression which should be in the range of 100+ psi (somewhat less on the smaller hp engines) and even on all cylinders.

2nd - With the spark plugs removed, rig up some type of spark tester whereas you can set a gap to be jumped. On magneto ignition systems.... and also the Battery Capacitance Ignition system OMC engines from 1968 to 1972, set the gap to 1/4". On the solid state OMC ignition systems from 1973 to the present, set the gap to 7/16". The spark should jump the gap with a strong blue lightning like flame..... a real strong blue snap!

If there was no spark, on engines from 1973 up, disconnect the RED main electrical plug at the engine. Remove the s/plugs. crank the engine via the starter solenoid (jumper bat term to small 3/8" term nut, not the ground nut) and observe spark. If spark is now okay as stated above, the usual cause is a shorted ignition switch.

If the above checks out as it should, and the engine dies out when throttle is applied or won't idle, it is usually due to one or both of two things. The carburetors are fouled, in which case the cure would be to remove, clean, and rebuild them..... or the timer base under the flywheel is sticking which would result in a retarded spark. If the engine will not fire/start at all even though you have the proper spark and compression, it's usually due to fouled carburetors.

To check the timer base for sticking (Engine Not Running), spin the prop to align the shifter dog with forward gear and while doing so, put the engine into forward gear. Now, while watching the timer base, slowly apply throttle clear up to full throttle. The timer base should move smoothly all the way up against the black rubber cap that is atached to the end of the full advance spark setting screw. If the timer base sticks, find out why and correct that problem.

Usually any sticking of the timer base is caused by one of the four retaining clamps being slightly too tight. Putting a very thin washer under the clamp cures that problem. Some boaters use a thin screwdriver to bend the clamp upwards slightly but I prefer the thin washer. The sticking can also be caused by having a faulty stator start to melt down, resulting in a sticky substance dripping down on the timer base nylon retaining ring.

 

[tashasdaddy]

Re: Can't run wide open after fixing regular culprits; HELP!

you have the classic symptoms of clogged high speed jets. when you cleaned the carbs, did you?

disassemble the high speed jets with the special tool and clean them and the seats?

install new needle valve and seat?

remove the core plug on top of the carb, and clean idle jets?

reassemble with a new carb kit?

read this, http://forums.iboats.com/showthread.php?t=158086

all these items are in the carb kit, except the special tool. here what the tool looks like. i made mine with my belt sander.

also did you do a link n sinc? and replace the impeller?

 

[kiddynomite]

Re: Can't run wide open after fixing regular culprits; HELP!

Thanks guys for your help. To answer a few questions; I checked the plugs and they had a good solid spark.

Tashadaddy, when I cleaned the carbs I took them apart, the seals were still good and the needle'n'seats were good. The jets were a little gunked up so I cleaned them thoroughly and put them back together. I know it was not the ideal cleaning but they were in pretty good shape, summer is halway over already and I was trying to save a dime. But they were spotless when I put them back together. How does the special tool work, and to really show how green I am, what do you mean by link n sinc?

 

[tashasdaddy]

Re: Can't run wide open after fixing regular culprits; HELP!

the high speed jets are deep inside the drain plug on the front bottom of the carb. the tool is made to go in that narrow hole and unscrew the jets, so the can be cleaned, it doesn't take much build up to restrict these.

the low speed jets are under the top core plug, which has to be pried out and replace with a new one, in the kit.

linc and sinc, is a step by step process, different for each engine, covered in the OEM manual, what it does is correctly sets the electrical timing with the operation of the carb, so the work in unison.

 

[jtexas]

Re: Can't run wide open after fixing regular culprits; HELP!

There's tiny little passages in there that you can't see into, so there's no way to visually determine that they're "spotless". Order the carb kits from iboats, $11 apiece, you'll have 'em in a few days. Disassemble your carbs & soak 'em overnight in B-12. The special tool works like a screwdriver, but ..........trust me on this............. don't try to remove the jets with a screwdriver, you'll end up mangling 'em. Without the tool, best you can do is clean 'em in place with a single-strand wire (don't risk scoring or scratching 'em up with a brush), & blast some aerosol carb cleaner through 'em.

Until you've done this, there's no way to rule out clogged hi-speed jets as your problem. Taking short-cuts with your carbs just means having to do it over again - summer's too short for that.

link & sync - process of syncronizing the carb linkages & spark advance. kind of complicated - you'll need a manual for the step by step - meanwhile, you can make sure the throttle valves are parallel, closed at idle, horizontal (not beyond) at WOT. And the timer base starts moving *before* the throttle valves start to open.

 

[kiddynomite]

Re: Can't run wide open after fixing regular culprits; HELP!

I will try this out asap - you have been a tremendous help, thanks!