throttling problem

[mucduc]

hey everyone. this is my first post on this forum. i have been using the forum for awhile now and i have been able to find pretty all the answers to my problems by searching. but now i have a question and have no clue anymore.

i finally got my 1985 50hp evinrude running good today while out of the water. my original problem was that when in the water at full throttle it would accelerate, then slow down, then accelerate, then slow down, and so on until it would just die. the boat sat for awhile until i started working on it again. at first it would have a hard time starting then only run for a few seconds. so i replaced fuel tank, all the fuel lines, fuel filter (i kept finding leaks in the fuel lines), cleaned both carbs and blew out the jets (a very small bit of junk in bottom carb). after i got it all back together it pretty much started right up with no problems. i even shut it off and let it sit and it still started no problems.

but then i put it in the water earlier today and it didnt really want to start and once i got it started and kept running my original problem came back. what do yall think

thank you
patrick

 

[a70eliminator]

Re: throttling problem

Have you replace the fuel line quick couplers or at least install new o-rings in them? It still sounds like a fuel delivery issue.

 

[mucduc]

Re: throttling problem

well kinda. the QD had a real bad leak and when i took it off the motor i sheared the head off the bolt so for a quick fix i just bought a male to male barbed fitting and hard wired the 2 lines together. i cant figure it out. the fuel pump pumps fuel so i know that works. there is that little red switch that is on the right side of the motor. right now i have it pointed forward. how i understand is that the red switch is for priming with pull starting. could this switch be a problem?

 

[tashasdaddy]

Re: throttling problem

vent open on fuel tank? arrow on fuel line bulb, pointing toward the motor? have you changed fuel lines to alcohol resistant lines. have you check compression and spark. hard start in water, idle speed needs to be increased. if will idle fine on muffs, but there is not any backpressure on the exhaust. set muffs idle high, the adjust in the water. read the TOP SECRET FILE, 1st thread in this forum.

 

[mucduc]

Re: throttling problem

vent open on fuel tank? arrow on fuel line bulb, pointing toward the motor? have you changed fuel lines to alcohol resistant lines. have you check compression and spark. hard start in water, idle speed needs to be increased. if will idle fine on muffs, but there is not any backpressure on the exhaust. set muffs idle high, the adjust in the water. read the TOP SECRET FILE, 1st thread in this forum.

vent is open. bulb is in right direction, not sure about the fuel lines (i bought them at napa), thanks i didnt even pay attention to that thread.

what is the reason i would need to adjust the carbs if the settings havent been change to begin with (i can understand if i just rebuilt the carbs and im fine tuning) but the guy who had it before me had it running fine.

 

[bktheking]

Re: throttling problem

(i can understand if i just rebuilt the but the guy who had it before me had it running fine.

It's not that the problem came back, it's that it was never fixed.

Guess I'm missing something, your post stated:

cleaned both carbs and blew out the jets (a very small bit of junk in bottom carb)

This is a change is how the carbs were set, cleaning is taking them apart, fuel flows differently when things are cleaned. But I don't think it's the problem. Check the floats for perferation, sounds like you have a float acting up causing the fuel flow to vary, had a motor do this to me, shake the float(s) and listen for sloshing. Better yet you want that thing to run like a champ, put new kits in the carbs, maybe even floats if it/they are bad. You might also have a bad needle and seat or a sticking needle,anything is possible.

Starting a motor on muffs and out on the lake can yield 2 different results, on muffs the fuel doesn't flow the same as on the lake, you can't hit max RPM on muffs. This makes sense, slow fuel flow at idle woudn't present a problem cause the floats wouldn't be rising and falling like at open throttle speed, it's a loping effect causing the rpm to vary BIG TIME.

 

[1946Zephyr]

Re: throttling problem

Great point, bktheking. I think fuel delivery and cleanliness of the fuel system are a factor here. Just for the heck of it, I would look over the electrical connections of the ignition sytem over really good too, while you're in there. Corrosion can mess with these a bit too.

 

[mucduc]

Re: throttling problem

i will be buying a carb kit today. i talk to a buddy who used to work on small engines and was talking about the float and seat either being stuck up to starve the motor for short burst or stuck down flooding the carb for short burst. after reading the top secret thread i realize i didnt do anything with the high speed jet. i didnt tear them completly down when i was cleaning it. i just took off the bowl and blew that all out then got a lenth of thin solder and cleaned the low speed jet and blew that out.

i saw that the there are a couple different brands of carb kits. they were pretty much the same price whether they came with new floats or not. im assuming that there isnt really any difference between quality of the kits?

 

[tashasdaddy]

Re: throttling problem

i have to disagree with this:

"Starting a motor on muffs and out on the lake can yield 2 different results, on muffs the fuel doesn't flow the same as on the lake"

the reason is that on Muffs, there is not any backpressure on the exhaust. the idle on muffs must be set higher than normal, then you take it to the water, and fine tune you idle, with back pressure on the exhaust.

 

[bktheking]

Re: throttling problem

i have to disagree with this:

"Starting a motor on muffs and out on the lake can yield 2 different results, on muffs the fuel doesn't flow the same as on the lake"

the reason is that on Muffs, there is not any backpressure on the exhaust. the idle on muffs must be set higher than normal, then you take it to the water, and fine tune you idle, with back pressure on the exhaust.

Agreed, Tash, I may not have been clear about what I meant. I'm not talking about idle here, i'm talking about the way the float reacts while under idle vs high speed operation. You can't attain high speed operation on muffs as you risk engine damage, on the lake you can run it "for real", the floats and fuel consumption will act different causing the up and down acceleration as mentioned.

 

[mucduc]

Re: throttling problem

from what i have been reading and what yall have been saying about adjusting the carbs while in the water im pretty sure you mean that once its in the water put in foward gear and increase speed then stop and adjust then keep doing that process as you would in a car. but the problem i have is that i dont have any lakes around that i can put in. only rivers, which i have floated down before cause i couldnt get the boat started again. my question is what is the likely hood of the boat stalling before i have a chance to get back to the dock or shore to readjust the jets. should i over set the jets with the muffs on just to make sure the backpressure of the water doesnt send me down the river?

should this be in another thread?

 

[tashasdaddy]

Re: throttling problem

your carb has fixed jets, no adjustments, you have to set the idle speed stop screw to set the idle speed.
as i said get it idling high, then put in gear, lower the speed to where it will still run in gear, with out stalling.

 

[mucduc]

Re: throttling problem

so in the top secret file about adjusting carbs would my motor fall into the single S/S adjustment needle valve? or 2 adjustable N/V? and this screw is the brass screw that is top dead center when looking straight at the butterflys of each carb? i dont remember if there was another screw bottom dead center.

and could this be the problem with the power gain and loss when in gear?

i just noticed that you are in jax. i live about 30mins north in camden county, ga

sorry for all the small questions.

 

[bktheking]

Re: throttling problem

There is only one adjustment, slow (idle) speed, the high speed jets are fixed unlike the older carbs from the 50's which had both high and low speed ADJUSTABLE jets.

 

[kenmyfam]

Re: throttling problem

One thing I have not noticed here is checking if there is enough fuel delivery to the carbs to begin with. (unless I missed that)
Could possibly be the root of all these evil's here.

 

[mucduc]

Re: throttling problem

im having a hard time trying to find a picture of what the low speed and high speed jets look like. i only saw 1 jet in the bowl. it kinda looked like this picture

is the high speed jet the bigger tube and the idle the smaller tube inside the big one?

http://i184.photobucket.com/albums/x175/pmaloney1974/Carb Rebuild/100_0938.jpg

 

[mucduc]

Re: throttling problem

and are these the adjusting screws?

http://i290.photobucket.com/albums/ll275/ffmartinpl/boat/100_0920-1-1.jpg

 

[tashasdaddy]

Re: throttling problem

those are the low speed jets, they should be turned all the way in, just snug. they are not adjustable, YOUR MOTOR HAS FIXED JETS, NOT ADJUSTABLE JETS. forget about adjusting the carbs, not possible.

top secret adjustment are for older motors than yours.

your high speed jets are deep inside behind the red mark. you need a special screwdriver to get them out. read this, it is identical to your carb.

http://forums.iboats.com/showthread.php?t=244013

 

[bktheking]

Re: throttling problem

and are these the adjusting screws?

http://i290.photobucket.com/albums/ll275/ffmartinpl/boat/100_0920-1-1.jpg

Ya my bad, this thing has no idle adjustment jet, just idle adjustment screw, busy household this morning.

 

[tashasdaddy]

Re: throttling problem

i'm still trying to be perfect also. we all make mistakes.