Mercury 1500 floods when off-level

[DHag]

Hi. I'm a newbie on this forum, and a relative newbie to boating in general.

I have a '79 Mercury 1500 that runs great until it is allowed to idle when not trimmed to sit level. It's on a '79 Champion Super V bass boat. The boat really wants the motor trimmed all the way down when starting out, in order to come up on plane as quickly as possible. Because of the angle of the transom, and the boat's far-back cockpit position, this means the motor is actually tilted far down in back.

If the motor is trimmed all the way down, and I allow it to idle there too long before opening the throttle, it floods and "loads up," and never gets power. "Too long" is about how long it takes to trim it down. I usually have to back off the throttle, then trim the motor up until it is level. Then it will power up and go just fine. Trouble is, when it's trimmed up like that, the boat wants to stand on its tail, and it takes way too long to come up on plane.

If it makes a difference, the motor has a hydrofoil stabilizer installed (looks like a Doelfin brand), and the previous owner removed the baffles from the exhaust.

A friend who had one of these motors told me that this is "nature of the beast" for Mercury motors. He says he has a 225 horse Merc that acts the same way.

It seems to me that it's getting too much fuel like this. I have checked the float levels, and they are right on spec.

It's hard for me to believe that Mercury would let this be "nature of the beast," or they would lose sales. I'll check any and all suggestions.

 

[Chris1956]

Re: Mercury 1500 floods when off-level

If is not a normal thing for this motor. In addition to having the carb float levels set correctly, make sure the floats have not absorbed fuel. The originals were foam and did absorb fuel. Replace them with then newer hard plastic floats. Make sure the little springs on top of th floats are intact. Also the fuel inlet needles can leak. Best to replace them and their gaskets as well.

After this, reset the idle mixture screws. Also rebuild the fuel pump, or at least check the fuel pump diaphram for leaks.

 

[DHag]

Re: Mercury 1500 floods when off-level

I took one of the float bowls off originally because one carb was overflowing when running. I noticed the float was foam when I took it out. I gave it a squeeze with my fingers but did not see any seepage around my finger tips. That's a trick that works with foam floats from car carbs, but these are a different type of foam. I did not weigh the float, but as I recall, it did feel a little heavy. I thought maybe it was just a denser foam than used in car carbs.

I did not see any springs on them, unless you're talking about the little spring clips that hold the needles to the float tabs.

The needles aren't leaking now, but I can't say the gaskets under the seats were in that great a shape.

The fuel pump seems to be working very well, but I'll check it anyway.

So basically, you confirm what I thought. If the carbs' floats are right (no absorption, no leakage), then the motor shouldn't do that.

Thanks. I appreciate it.

 

[emckelvy]

Re: Mercury 1500 floods when off-level

There are supposed to be little springs inserted into the center depression at the top of each carb float.

The spring pushes on the lever that actuates the carb needle; the float is never intended to directly ride on the lever.

If these springs are not present in your floats, that might explain your carbs' strange behavior.

The newer-style floats are hollow, hard plastic and tend to have more "flotation value" than the old floats. I think this puts a bit more pressure on the needle which makes it seal better. I've noticed that it's quite a bit harder to "blow by" the needles by pumping the primer bulb real hard, with the later floats.

I expect just changing to new-style floats will fix your problem right up. If that doesn't do the trick, a set of new needles/seats are in order.

HTH..........ed

 

[DHag]

Re: Mercury 1500 floods when off-level

There are supposed to be little springs inserted into the center depression at the top of each carb float.

The spring pushes on the lever that actuates the carb needle; the float is never intended to directly ride on the lever.

If these springs are not present in your floats, that might explain your carbs' strange behavior.

Are you talking about this type of float? I can see the spring in the top of this picture.

However, mine has this type of float. No springs that I can find.