Carburator adjustment ?

[glennj3]

Carburator adjustment

1987 470 Mercruiser, she sat up for about 2 years on the trailer under a shed. I put new batteries in, took her to the local shop, complete tune up and an old water leak repaired. They bypassed my fuel pump and used an outboard tank to run the engine. It still did not run smoothly for them due to not have a constant fuel pump pressure.The engine did not run well when I got her home. I removed the fuel pump, replaced the fuel line, cleaned out all of the garbage from that filter and replaced, removed the carburetor, cleaned and put in a overhaul kit. She now cranks up great, smooth idle but she hesitates (stumbles) sometime when increasing the throttle.
It is very hot outside and I am using the water hose to run her. The idle mixture was out 4 turns when I removed the carb. After overhaul I turned it out 2.5 turns initially. I had to turn it out about 4 turns again to get her to run smoothly.
The fuel was old, I put some fuel foam (to remove water and sludge) mixed in some fresh fuel. Idle is still at about 700 RPM. She shifts into gear easily.
Trying to figure out if the accelerator pump is moving when it should? I did not change any size to the rods so they should be the same as before overhaul.
Trying to get her to take the gas without stumbling! I will run fast but has to get through that stumble just at the start of increasing the throttle.
Thanks for your help. May end up taking her back to the shop, but she will set there a few weeks!

 

[glennj3]

I posted earlier but do no see it anymore. I had gone into much detail but now I don't care to go through it all again.
In short, I overhauled my carburetor cleaned it etc. Cleaned the fuel pump and filter, replaced the fuel line. 440 Mercruiser, 1985. The fuel is old but I put some fuel foam (absorbs water and sludge), put some fresh fuel in the tank. Had a complete tune up at the shop done. I chose to overhaul the carb myself and save $250.
Now, she cranks up and runs great, I have a hesitation (stumbling) most times I try to give it acceleration.
The idle screw is about 4 turns out, anything less and she does not run well at all. RPM is at 700. She engages gears well. I am using the garden hose on the trailer as the lake is not close by.
Any advice? Thanks.

 

[stonyloam]

440? Maybe 470? Anyway 4 turns out is a bit much, should be about 1 1/2 Could be some crud in the idle circuit. If you screw it farther out does the RPM change? If not it may need cleaning. The hesitation may be related to the accelerator pump. Check the timing.

 

[JerryIrons]

My feeling is that if you need 4 turns out to make it run smooth, and stumbling on acceleration, your carb still isn't right. How did you clean it? Also check the timing like stony said.

 

[Rick Stephens]

Old fuel is old fuel. Seafoam won't rid you of either the crud or the broken down ethanol.

If you have a bad throttle/RPM range after a carb cleaning/rebuild then something isn't clean yet in the carb. That has to be the most common problem with carburetor rebuilds, even shops get it wrong on a regular basis.

 

[glennj3]

Thanks, when things don't work like they should and I have several variables, results are always changing. Since my post, I managed to get her going pretty good so I took her to the lake for an in the water test. I ended up driving all around the lake at slow, then normal cruise. On the return I opened her up for just a bit. Shortly afterward I saw the temp go up some but under 175 degrees and it stayed there until I slowed down at the boat ramp. The engine stalled, I cranked her back up but she was idling poorly. I then notices she was running hot (just over 175) so I cut her off and flagged some friends down for a tow in.
Pulled her out on the ramp and a lot of what looked like lake water came out of the boat plug when I removed it.
Checked the coolant, it was gone out of the internal system.
Since I did not change out the outdrive water pump I figured it broke, Pulled it off and it looked like new, I replaced it anyhow since it was 2 years old but only used twice.
I pulled the thermostat, check it and it worked in the specified perimeters and looked new so I replaced it.

Puzzled, I replace a gallon and a half of coolant, cranked her up using the garden hose, removed the cap. Very suddenly the coolant started blowing out of the cap port and the engine started running hot. Stopped in my tracks.
Today I pressure tested the cooling system, it would only hold 10 lbs, and was blowing water out through the upper outdrive area, I could not see the exact spot it was coming from but all of the hoses looked good.
I came home and removed the gaskets from the front of the heat exchanger and fresh water came out and there was some antifreeze (green) on the bottom of the Heat Exchanger.
So I think the carburetor problem has been replaced with a cooling issue. The heat exchanger is only several years old from new, the inside looks very clean.
What or how should I test next?
Thanks,

 

[stonyloam]

Do a compression test, and look at the exhaust elbow gasket.

 

[glennj3]

Thanks, I removed the heat exchanger from the boat. With the caps off of both ends I can see through all of the small tubes, everything looks smooth and clean. I washed everything out with a water hose and it was clean.
I used the two large hoses (that should be the closed cooling system) held them up evenly and filled one with water until the other was equal level. It did not hold the water level up and water was slowly pouring out of the end of the exchanger. I would assume there is a hole someplace in there where it should not be?
If this is so, can I have this one rebuilt or is it best to just buy a new one. They cost bucks!
Terry, do you mean to do cylinder compression tests? What would I be looking for at the elbow gasket?
Thanks again.

 

[stonyloam]

Sounds like a hole in the exchanger. Yes a cylinder compression test, the fact that coolant was blowing out may indicate a head gasket problem, and 470's are known to have hug problems. Always a good thing to check. For the exhaust elbow gasket, it separates the coolant from the raw water, so if it leaks you can loose coolant out the exhaust. Look for a corroded surface or any signs the gasket is bad, check rhe elbow fir rust holes.

 

[glennj3]

My mechanic said to never crank the engine with the radiator cap off, it will always blow antifreeze out, like a volcano!

 

[stonyloam]

My mechanic said to never crank the engine with the radiator cap off, it will always blow antifreeze out, like a volcano!

What??? I don't think so. Did he explained why? I think you might want a second opinion on that!

 

[glennj3]

Stony, I replaced the HE today, filled with antifreeze and she ran well without heating or leakage problems. I did not run with the cap off but did top her up after she cooled down some. At this point all seems to be working well. The reservoir is filled so when I check her tomorrow antifreeze should be at the cap.

I am having initial start up problems, does not want to crank up easily as she should. Engine likes to stop like it has too much compression, then will back fire mist from the carburetor sometime. No popping backfire stuff. I always need to touch the choke flap a little to get her to run, when starting from cold. Cranks pretty well after the initial run.
The idle jet screw is out 4 1/2 turns, anything less and she hesitates and runs ruff, will not accelerate.
At 4 1/2 turns she runs so smoothly and accelerates well except for 1300 to 1500 RPM, very ruff, then smooth's out and runs strong. The tachometer also jumps around a lot at that point, like a short.
I hate to pull the carburetor apart again because it was so difficult to put back together. I did not remove choke valves so the choke rods are difficult to work around. I did well to not bend the float while putting her back together. It would be best if I could remove the rods in order to put it back together efficiently!
Idea on how to do that?