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Mercruiserbackfires no power

"Paul.
You said you had tried

"Paul.
You said you had tried a different tank with no change. Is this a 4bbl or 2bbl carb engine?
Is this an electric pump?
If not electric pump and you feel this is the problem,find an electiric pump and remote tank and connect it and see if it helps. Any automotive style electric pump should do for this test.
You sound like your location is about the same type as mine. The middle of nowhere. I hope you have a parts store close you can find a pump and some fuel line at.

What is the area you are located in. Nothing to do with the boat just wondering."
 
"I am in small community calle

"I am in small community called Port Alice on the north end of Vancouver Island in BC. It sits on the Quotsino Sound. It is about a 25 mile boat ride to the mouth of the sound to open water in the pacific. Great salmon, halibut and ling cod fishing. Have to outside for salmon right now, but before too long they'll be coming into the inlet.

It is a 2bbl carb. We replaced the fuel pump which is electric. When tested previously we attached the auxillary tank to the inlet on the fuel pump.
I was thinking a gravity feed would take the fuel pump out of the equation all together. Also I was thinking of lifting the siphon tube about 1/2 way up in the tank to get it off the bottem and see if that makes a differnce.

Right now I can't tell if we have two problems or one, but it is clearly not getting fuel now. If the lower end has to come off, is this something that I can do?
Where are you located?
Paul"
 
"Paul.
Yes ypu can handle the

"Paul.
Yes ypu can handle the removal of the out drive. You need a 5/8 & 9/16 end wrench or socket for this.
The shift must be in forward for the drive to come off. Just remove the trim cylinders from the drive and tie them up out of the way and remove the 6 nuts holding the drive on. It's kind of heavy so it's a good idea to have some help.
When reinstalling it make sure the shift lever on the front of the drive is pointing forward so it goes back into the linkage rod on the gimble ring. You'll see this very clear when the drive is removed.
Take care removing the drive so the gasket is not broken. Depending on the condition of the gasket it should be re-useable but may need a little sealer.
I'm not sure of the gravity feed idea, it is iffy at best. This sounds dangerous to me. You would need at least a gallon of fuel for it to have enough pressure to keep the carb full. You may be able to spray starting fluid into the vent on the carb float bowl witch would add extra fuel into the carb.
A can with a spray tube on it that you can make sure of where the spray is going.
If you have a full can it should be able to keep up enough for you to tell if this is the problem.

I'm located in another great fishing area. We don't have the fish you do but have some of the best trout fishing you can find. Rainbow,brown.lake trout,sockeye salmon in the fall. A little place called Grand Lake in Colorado. 8200ft altitude. 30 pound lakers are common.

Back to the boat. When you get the drive off where the shift rod goes through the gimble ring is where these flappers with be if they have come loose. You can't miss them if you're looking for them.
They can be a real pia to remove from the port. They are hard plastic and do not break easy. Except from their mount of course. Only two ways to remove them. Remove the shift rod(witch never wants to come loose) or hold it with vise grips and cut it with a cordless sawsall.
I'll be on and off here this morning but I will check back in a little while. Good luck."
 
"Not Me,
Before we pulled the

"Not Me,
Before we pulled the boat my neighbor suggested that we take another stab at the carb. We took it off, took it apart and blew it out. He also reset the float to allow in more gas. For the first time we were able to get the boat onto plane and with full throttle 24 knots. Clearly it is now getting gas and has improved the situation. It is still underpowered, since I never had to use full throttle to cruise at 27 knots. My tach is not working so I don't know rpm.

When running my neighbor pointed out that the intake manifold was very cold and the base of the carb was so cold that it was condensing water. Do you know what would cause that; it is a symptom if another problem or same problem. Does it indicate an intake leak, loose manifold?

Still plan to remove the outdrive after we have done what we can in the water. Want to make sure that it isn't more than one problem.

I could live with 30 lb lake trout; sound we are both in ideal places,
Paul"
 
"Paul.
That is intresting.

"Paul.
That is intresting.
I thought that the carb had been rebuilt. I now need to ask if the main jets were cleaned with a tip cleaner for a torch or a small wire?
If this was over looked it would cause this type of problem.
I never gave it another thought since you said the carb was cleaned.
These jets have very small holes in them and plug very easy from old fuel. Make sure the jets are clear.
This is more likely than the exhuast. The engine would run about the same with either problem.
I'd pull the jets first to be sure they are clear as well as their ports.
Sorry,I guess I should have asked about this before. I took it for granted that the person doing the carb repair knew to check this.
I sure hope it is the cause.
If it is getting up and going it is not the exhuast. No matter what you did it would no go with a blocked exhuast system. Unless it is clearing out on it's own. (nest). The jets are in the bottom of the float bowl. Little brass plugs with a screw driver slot to remove the. Careful with them. You need the correct size driver or they may round out. Put a fair amount of down pressure on the jet while trying to remove it. It should break / snap loose.
Paul this post is getting to long. Can you send your e-mail address."
 
"Here's an update on where

"Here's an update on where things stand now. As I mentioned yesterday, we had only replaced the needle valve and accelerator pump when we first went into the carb. Yesterday we completely took it down removed the jets and pushed wire through the openings and blew it out with an air compressor. As you pointed out I believe that has been the problem all along.

Yestrday afternoon went into the next towsn and bought some fuel treatment, retimed it and we ran the boat again. It improved on power; we had it running about 28 knots at full throttle. Still under powered, but with out a working tach on the boat its hard to know more. When I reset the rpm and timed it, it seemd to pulse slighty off of the 10 degree btoc. Something is stil odd, but it seems like I should be able to get my son out fishing; he still has about five days here so we have some catching up to do.

Not Me, thank you for hanging in there with me on this. Your advice has been invaluable. If you send me your email address I'll let you know it goes tomorrow when we go out.
Paul"
 
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