Idling/Flooding Problems

dsisk

Recruit
Joined
Jul 5, 2014
Messages
5
I purchased a 94 20ft Lowe pontoon a few months ago. It's a 70 hp 3 cylinder 2 stroke. The boat has not idled right since I bought it. After replacing the fuel lines, bypassing the VRO, cleaning carbs, new plugs, and replacing the head gasket, I did a compression test. Results: Top-115, Middle-145, Lower-145. I know this is a problem. I took it to a mechanic, said top cylinder is scored. So I got to work on it, ordered a manual, and took everything off. Took the powerhead to a machine shop and the top cylinder was bored .30 over. Middle and lower were both honed to polish them up. Ordered new piston head and all the gaskets I needed to replace the old. Put it all back together and threw it on the the boat. Compression test is now, Top-140, Middlie-135, Lower-140. All good. Mixed up fuel, 25:1, as indicated per manual. Took a couple cranks, but it fired up. Ran for about 30 seconds and then died. Boat runs fine above 1500 rpms, anything lower it stalls. I put the boat in the water to see if some back pressure would help, no luck. I did some tweaking while the boat was at the dock to the carbs. Started up, and same thing. I noticed that there is alot of fuel bubbling to the water surface, guessing its coming out of the exhaust. I was told a while back to back the slow idle screws on carbs out to 2 and a half full turns. The manual says 1 and an 8th turns. Do you think this is flooding my engine having the screws out 2 and a half turns? Also when i rebuilt the carbs, i replaced the floats and adjusted the drop as instructed in the kits. I noticed that one of the floats was a little sticky. Do you think maybe this float is stuck open and is contributing to the flooding? When the boat runs for its 45 seconds, I can hear a "ding" coming from the motor, but Im not sure exactly where it is coming from. Sometimes its immediately after the boat shuts off and sometimes its a minute or so behind. Im curious if this ding noise is the carb float sticking. Any suggestions you all have would be great.
 

ahicks

Captain
Joined
Sep 16, 2013
Messages
3,957
You mention VRO, so I'm guessing you have a Johnson or Evinrude. My first suggestion is you post these questions in the engine section of this forum to let some guys that are much more knowledgeable than I am have a crack at what's going on. I do have a few thought. First, if it's flooding at 2.5 turns, why not try it at the factory suggested 1 1/8 turns to see if that helps? Second, reassembling a carb with a potentially sticking float was probably not a good plan. Better would have been to figure out what was causing the sticking and take care of it while you had it apart.

On my '89 40hp VRO (which is working perfectly), there's an "enrichening" device that is used instead of a conventional choke. It amounts to a solenoid, that when opened, dumps a ton of fuel in each cylinder. It might be worth checking to see if that's working properly? If it's not closing properly, or you are holding the key in the "choke" position too long, it could easily be flooding your engine.

Last, it should idle fine with no back pressure required.

Best of luck!
 
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dsisk

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Jul 5, 2014
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Thanks ahicks. Ive been working the last couple of days. I'm gonna head down to the boat tomorrow and pull the carbs off again and clean them out. Yes its a Johnson, sorry forgot to post that. This is my first boat, so still learning all the parts. I didn't think it was sticking that bad when I put it back on. It would drop with light touch, it just didnt freely drop like the other two floats did. Ill check the primer solenoid next to see if its sticking, but when i push the key in to prime i can hear it open and close.
 

out 2 launch

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Dec 11, 2008
Messages
77
I took it to a mechanic, said top cylinder is scored. So I got to work on it, ordered a manual, and took everything off. Took the powerhead to a machine shop and the top cylinder was bored .30 over. Middle and lower were both honed to polish them up. Ordered new piston head and all the gaskets I needed to replace the old. Put it all back together and threw it on the the boat.
Was it ever determined what caused the scoring?
 

dsisk

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Joined
Jul 5, 2014
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That's a good question. I bought the boat from this guy, not knowing anything about them. He started up on muffs and it ran fine, water pissed out like it was suppose too. He seemed like a legit guy, was thorough with showing me everything. He told me that he posted it on craigslist one day and went out and fired it up and noticed that there was not water coming out. So he took it off craigslist and off to a marine mechanic where the impeller was replaced, said it was shredded. Who knows when this happened. About a week after i bought it i called the guy and told him what it was doing. He said that he started having some issues with it towards the end of last boating season (which he failed to mention to me when i bought it). If I had to guess it overheated, but im not sure why the alarm didnt go off. Anyway, when I tore down the motor I found pieces of the impeller in the coolant tank on the side and some wedged in the thermostat. I guess I still don't know why the top scored. I do know that right now I have good compression, I was going to periodically check it, if I can get it running.
 

rogerwa

Commander
Joined
Nov 29, 2000
Messages
2,339
As for the float, if you can look into the throats of the carb while you pump the bulb, you can see if fuel flowing into the carb because the float sticks. I would think the float would stick more closed than open, but who know.. The bulb should also be hard. If you can keep pumping the bulb, the fuel is leaking somewhere. I would put the idle mixture at the rated turn and an eighth. and adjust from there according to manual.

I would guess your scored cylinder came from overheating caused by restricted passages from the destroyed impeller. Depending where your overheat sensor is it may not have been set off.
 

steelespike

Supreme Mariner
Joined
Apr 26, 2002
Messages
19,069
As far as I know the factory setting is too get it running then you need to adjust to the best idle.I think the idle is supposed to be about 700 in gear.
 

Silvertip

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Joined
Sep 22, 2003
Messages
28,758
Idle "speed" and idle "mixture" are two different settings. Idle mixture is set for by using the factory INITIAL setting just to get the engine started in the water. Back pressure has a definite affect on idle quality. When warmed up, adjust the idle SPEED to factory spec or as close as you can get it. Then starting with the top mixture screw, turn it inward slowly (1/8 turn at a time) until the engine begins to bog. Note that setting. Now rotate the screw counter clockwise until it begins to bog. Happiness is somewhere in between those two settings. Rest the idle SPEED again and repeat for the next carb. Reset idle speed and repeat for the next carb. You may need to repeat this process at least twice to get things perfect. Idle speed should be set with the throttle cable disconnected. When everything is adjusted properly, adjust the throttle cable. All of this is covered in the service manual for your engine. If you work on your own stuff, this is the first tool to buy for your engine.
 

dsisk

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Joined
Jul 5, 2014
Messages
5
So I set each carbs idle mixture screw at 1 and 1/8 turn. Started the boat up, but now I can't even keep it running even with throttle. I didn't know that I needed to remove the throttle cable to set idle rpm. I'm going to turn the mixture screws out a little so I can atleast keep it running long enough to make further adjustments. I'll pull off the air silencer an look into the throats while pumping the bulb. The bulb does stay firm though. I still don't know where the "ding" noise is coming from. I'll post results. This boat has been giving me fits ever since I bought it. Thanks for the info. Hopefully we can get this issue taken care of.
 

MaPaHa

Petty Officer 1st Class
Joined
Jul 6, 2012
Messages
239
I have a 150 Evinrude that had a vacuum leak between the throttle plate and the engine. There's a "O" ring that goes between them and it has to be in place everywhere before it will seal. I used tacky red grease to hold it in place during assembly. On the V6, there are only two throttle plates but 3 carbs on each plate and you can rebuild the carbs without taking the throttle plate off which is what I did the first time. Finally I went deeper and found one of the O rings was out of place and leaking vacuum. Replaced them and it runs fine.

Because your's is not idling properly I would look for something like this. Mine was also a VRO; notice I said "was".
 

glust

Petty Officer 2nd Class
Joined
Jan 23, 2012
Messages
141
I know you mentioned cleaning out the carbs, but it sounds to be like its either a vacuum leak somewhere leaning out the mixture, or a jet is still plugged resulting in a lean mixture. Try spraying some starting fluid around motor but not into intake. If the motor revs there is an intake vacuum leak. I have cleaned out carb jets before just to have is suck a dirt ball or something I loosened up in the cleaning process.
 
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