1980 25 hp Mercury Long Shaft wont start

[Arkman]

Last fall I received a 25 HP 1980 mercury. I finally had a chance to try and fire it up and I'm having a hard time getting it to fire.

First things first...Here is what I did.

1. Replaced spark plugs and checked to make sure I have spark. Both cylinders I have what I think is good spark.
2. Checked the compression. I have about 110-115 on both cylinders.
3. Checked the fuel system. Originally I had a leak around the cork gasket on the side of the fuel pump/carb. I would prime the bulb and it would just shoot gas out the side. I've replaced the blue plastic cover and the cork ring and now there is no leak. I flushed out the fuel system best I can as well. Cleaned out the filter and so on.
4. I pulled the carb off and cleaned it out best I could. I didn't replace any parts or anything, but cleaned it out with carb cleaner and compressed air. I also did some reading and decided to adjust the idle screw back to the starting position 1 1/2 turns out.

Before I pulled the carb off, I tried to start it. I pulled and pulled and could get it to fire. It sounded like it wanted to go, but wouldn't quite get there. Thats when I decided to pull the carb. After I did that I pulled a few more times and it finally ran. It wouldn't idle, but I was able to get it started and then give it some gas and it ran. I don't like to have it on the muffs above idle so I didn't do this very long at all. I backed off and it died close to idle speed.

After that I could get it to sort of fire again, but not really start. One thing i noticed is when I prime the bulb I can force fuel out the main jet. I'm not sure if this is normal or not, just something I noticed.

Here is what I'm wondering. I don't really have much time or money to dump into this, but I'm wondering if you guys have any insight on what I could do next. I know one next step would be to disassemble the carb completely and redo it all. I think I'll probably skip that if it comes down to it, but I thought I'd see if there was anything else I'm missing.

I don't know a ton about outboards, but I did spend a fair amount of time rebuilding my 1968 20 hp merc so I have some experience. And from what I can see there is no obvious issues. It seems to have both fuel and fire.

Thanks in advance!

 

[flyingscott]

You need to rebuild that carb with a good kit that has the pump gaskets and primer assembly easy to do. You have one major problem you should NOT be able to force fuel through the main jet with the primer ball. That indicates a bad float level or bad needle and seat. Don't think you can avoid the carb rebuild.

 

[Arkman]

Ok. Thanks. I was guessing that forcing the fuel was something that was probably a give away of an issue. I've never had to mess with the float on a carb (i've been lucky they are just fine in the one I messed with). I'm not sure what I'll do next. Getting the needle doesn't seem very easy. I'll maybe pull the carb off again and see if I can figure out out to adjust the float level. Maybe try that before the needle. Replacing the carb gaskets and so on doesn't seem to expensive or difficult so I'll probably try that too.

 

[flyingscott]

Getting the needle out is extremely easy it is under the float pull the float and the needle comes out.

 

[Arkman]

Yeah. I saw where it was when I pulled the carb out. Any advice on what to do or what to look for when I get in there? I don't really know much about adjusting those. I was hoping that I can just adjust what is there at first. I know it all needs to be replaced but nobody in town really has parts so...I was hoping to just adjust and see if I make a difference. If nothing else, see if I can get it to stop spitting fuel out that jet.

I've been doing some more research on carbs to understand a little bit more of what they do and how they work (not much better, but a little). There is a capillary tube (i think is what it is called). A brass tub sticking out on the fresh air side of the carb, before the choke valve. When I prime the bulb a bunch fuel comes out there too. This is something else I don't think is supposed to happen right?

Also, I was looking at the diagram more and found out there are two "main jet" labeled. There is one labeled main jet (#1399-8177) which is on the bottom of the bowl, and then there is one labeled "Main Jet - Back Drag" (#1395-6202) which is above the fresh air opening, more towards the top of the carb. The top one is the one I'm getting fuel coming out of. If that makes a difference.

To me what might be happening with the fuel is that the float doesn't actually float or something to that affect. I'm assuming that what should happen is when I prime, the bowl would fill up and the float would rise until it closes off. Then I couldn't force more fuel in, but instead it is not closing and I can keep forcing fuel in?

I only have a few hours every couple weeks to mess with this. Tonight is one of those nights, and I can't get any parts in town, so I figured I'd try and play more to see if I can get any closer before I order some parts. Thats the only reason I'm wanting to mess with it before I get the carb rebuilt.

 

[flyingscott]

Yes you definitely have a needle and seat problem. There is another possibility you do not have a choke on that carb you have a primer that shoot fuel into the motor for easier starts. If that diaphragm goes bad it will flood the motor. To adjust the float there is a measurement but just bend the brass arms a little at a time.

 

[Arkman]

YOU ARE THE MAN!! I tore it down and just bent that little flap on the float. I just eyeballed the needle location, so when the float was all the way up the needle just barely stopped on the seat. Put it back together and couldn't force gas through the jet, so I pulled and it started. Ran for a while. I turned it off and let it sit and it fired right back up. Seems to be in much better shape. I'll order the new carb kit and go from there.

It still started pretty tough that first time. 20 or more pulls. Will redoing the carb help that or is there something else I might need to do?

 

[MH Hawker]

yes that should help a lot

 

[flyingscott]

The primer could be bad you will get a new one in the kit. Make sure your carb kit has the fuel pump gaskets and the primer assembly. Also do a compression test you want to be about 120 psi on each or at least over 100 psi.

 

[thomas15]

A couple of other things I would do if it were my motor. I would replace the waterpump impeller and I would replace every single inch of fuel line. Then run on either ethanol free gasoline or use an ethanol additive.

 

[Arkman]

Thanks for the advise. I am planning to do that sometime soon. I am pretty sure the fuel line is brand new right before I got it. It looks newer than the stuff I put on my other motor a few years ago. I did a compression test right off the bat and I was at about 100-115 on both. I would think I'm within range of acceptable?

This is what I found for the kit, but when looking at other sites it doesn't look like the primer is included? I think it is listed as "enrichment valve".

http://www.iboats.com/REPAIR-KIT-CARB/dm/cart_id.522037568--session_id.138409252--view_id.1635858

 

[flyingscott]

That looks like it.