30 hp johnson cycling at high speed

[farfel]

have a 1999 30 hp ele start have dismanteled an cleaned the carb also the fuel pump because the engine started cycleing up and down when i opened up the throttle. there are no fuel leaks compression is great new plugs fresh gas idles like a kitten. this happens intermitintly after ive been running a while then it only runs at low speed. give it a while and crank it up and it runs great again until the next time. ive checked everything i can think of to no avail. any ideas?

 

[Daviet]

Re: 30 hp johnson cycling at high speed

Sounds like a high speed jet problem. When you overhauled the carb did you remove the high speed jet and clean it? Item #19 below.
http://www.ishopmarine.com/ishop/js...nown&isFrPG=false&forItemCode=&pCode=C0066558

 

[farfel]

Re: 30 hp johnson cycling at high speed

when i removed and disassembled the carb there was no high speed jet and this was the first time it was ever disassembled prior to this problem the engine ran like a dream at wot

 

[Cofe]

Re: 30 hp johnson cycling at high speed

I agree with Daviet, there is a high speed jet #19.

 

[farfel]

Re: 30 hp johnson cycling at high speed

ok i'll see if i can buy that jet and install it
will let you know what happens

 

[Daviet]

Re: 30 hp johnson cycling at high speed

If there were no jet in the carb, it probably wouldn't run. Are you sure there is not one in from the factory, it takes a special tool to remove it. I made one by regrinding a screw driver.

 

[Cofe]

Re: 30 hp johnson cycling at high speed

The #19 high speed jet in your carb is listed as a #59D Orifice. The size of the hole in the orifice is 0.059 That is roughly twice the gap distance on a spark plug for a reference.

 

[farfel]

Re: 30 hp johnson cycling at high speed

no there was no jet.and there were no threads for it to go into what i did notice was thgat in the brass tube that goes up from the center there was another tube in it that sipons gas up i cleaned this also with a fine wire and blew it out. friday when i ran the boat the engine ran fine but after about an hour it started cycling again. cant be dirt as i have a fuel filter from the tank which is also new and the inside of the carb is spotless

 

[farfel]

Re: 30 hp johnson cycling at high speed

thanks for the specs but please read on

 

[Daviet]

Re: 30 hp johnson cycling at high speed

Can you post your model number, I am confused by what you are saying, and don't see a 30hp with a carb like you are describing.

 

[farfel]

Re: 30 hp johnson cycling at high speed

found the jet pulled it out it was clean no obstructions. engine model # BE30BAEEC dont think its a carb problem pulled the plugs again they are clean (surface gap plugs)

 

[Daviet]

Re: 30 hp johnson cycling at high speed

You are going to have to trouble shoot this when the problem is happening since it comes and goes. Use an inductive timing light to check spark on both cylinders when it is acting up. If spark is ok, it is most likely a fuel problem, since it comes and goes I would expect that the compression is ok. It might not hurt to double check the compression to get a basic check of the engine.

 

[farfel]

Re: 30 hp johnson cycling at high speed

compression on engine is exellent 140/145 spark is ok it doesnt miss on idle purrs like a kitten
hole shot is great up on plane in no time. wot boat does about 28 mph. i run about 5 miles to my favorate spot no problem put-put around for a while no problem turn it off fish for a while go to another spot no problem start going home get the boat on plane run about 5 or10 min and it starts acting up so i back off the throdle and it runs smoothly put it in neutral then slam it forward it takes off like a rocket runs g ood for about 5min and starts cycleing again back off throdle until i'm doing about 7-8 mph and it runs fine all the way back to the dock just don't know whats up with this thing never saw this before

 

[Daviet]

Re: 30 hp johnson cycling at high speed

It sounds like an electrical componet is overheating and causing some ign problem. Check it while it is acting up and see if you are loosing spark on a cylinder.

 

[farfel]

Re: 30 hp johnson cycling at high speed

coils ?

 

[farfel]

Re: 30 hp johnson cycling at high speed

well took the boat out today when it started cycling again i put a spark tester on first one cylinder than the other no problem. spark is fine. took the tester off and ran the engine again. it was still cycling so i put it in neutral and slamed the throdel wide open. still cycling did it again ant it ran fine no problem slowed to an idle (trolling speed) putt-putted around for a while opend it up again .
no problem. I am baffled

 

[Monte1961]

Re: 30 hp johnson cycling at high speed

After rereading your first post again, I suspect the carb/s for what ever reason are running themselves out of fuel @ wot. I would check fuel pump pressure and volume. Good luck and tell us what you find!

 

[farfel]

Re: 30 hp johnson cycling at high speed

i think you're probably right i've been thinking the same thing if i remember correctly the diaphram in the fuel pump looked a little bellied probably from alcahol in the gas. i will order a new diaphram install it and let you know. bnearest place to get marine gas is in port canaveral which is pretty far away. maybe i should get a spare as they are pretty cheap.

 

[farfel]

Re: 30 hp johnson cycling at high speed

ok here we go again. rebuilt the fuel pump it ok pumps fine. finaly took the boat out this morning it ran the way it's supposed to. coming back from fishing i had to go slow as it was very rough out when the wind picked up. so it ran nicely at 8mph. got to smooth water and throddled up and it did the same thing like it was missing lowered the speed and it ran fine again. did this several times and it always started missing. think maybe temp. has something to do with it as when the engine sits for about an hour it runs fine again. so maybe something heats up and only partialy fails?

 

[Daviet]

Re: 30 hp johnson cycling at high speed

Use a timing light and check the spark on each plug wire when it is acting up, if both plugs are firing correctly, you have eliminated the complete ign system. You say the plugs are the surface gap type, swap them out for the center electrode type and see if it helps, I have had problems in the past with the surface gap plugs, especially at lower speeds.