1990 90hp Carb Springs & Fuel line questions

[mitchbuck]

I disassembled, cleaned, and put new gaskets on my carbs this week for the 2nd time in two seasons (last year I also replaced the idle needles). Anyways, I noticed a couple things and have two questions.

1) Last year I replaced the fuel lines on the carbs themselves however they appear to leak a little. I had used marine grade fuel line that I had purchased at west marine that was the same diameter as what was on there previously. Can anyone confirm what the diameter of the fuel lines on the carbs should be and whether there is a specific kind of fuel line I need to be using (manuals and ********** don't appear to indicate this).

2) The choke plate on the top carb has trouble fully opening (~90% open) and I realized that the return spring on the top carb is smaller than those on the center and bottom carbs. The return springs on the center and bottom carbs are the same as the ones on the throttle cam on the other side. So the obvious answer is someone replaced the top return spring at some point with the wrong size spring, but in the carb rebuild kit that I got last year there were two sizes of springs So now I'm not sure if they give you both sizes either to 1) cover all bases, or 2) the center/bottom carbs need smaller springs, or 3) if the carb kit was put together wrong. I have all the springs, just need to know which one(s) I should be replacing.

Thanks in advance!

 

[Jiggz]

Re: 1990 90hp Carb Springs & Fuel line questions

As for the fuel lines, I am not sure about the specific size but are the lines leaking even with proper hose clamps? Usually, this is either a 1/4" or 3/8" ID fuel lines. As for the carbs, all three carbs are identical except the lower two has different fuel inlet fittings (T's instead of an elbow), hence the difference in the model number. This means that the spring on the top carb may have been replaced with a wrong size and probably was not preloaded enough to fully return the choke plate in full horizontal. Double check there is no binding in the choke linkage and make sure you do not put too much pre-loading on the spring otherwise, the choke unit may not be strong enough to pull the choke plates.

 

[mitchbuck]

Re: 1990 90hp Carb Springs & Fuel line questions

The lines are leaking when using either zip ties or hose clamps! That's what I'm suspecting is that the top carb spring was incorrectly replaced....

 

[Jiggz]

Re: 1990 90hp Carb Springs & Fuel line questions

If the proper size of fuel lines were used, they should fit tight to the nipple of each fuel inlet fitting. Snugly is not even the correct term but tight that it requires effort to insert them in. You might want to verify the size of the hoses or even better verify the leak is actually from the hoses and not from the vent hole of the carb. If you can post a pic it will help very much in the diagnosis.

 

[pnwboat]

Re: 1990 90hp Carb Springs & Fuel line questions

Double check to make sure it's not the fittings that screw into the carburetor that are actually leaking. The fittings sometimes have a dark red colored hard sealant on the threads. The sealant cracks and deteriorates with age and the fittings start to leak.

 

[mitchbuck]

Re: 1990 90hp Carb Springs & Fuel line questions

Update: SO I was wrong the springs as I had the correct ones in the kit. I replaced the bad one without too much trouble. Once I got the choke butterflies set properly, I fired it up and it was running good! Then I noticed fuel leaking out of the fuel lines on the carbs.....the fittings were dry. Turns out I installed 5/16 in ID fuel lines on the carbs so they are too big. Does anyone know what ID diameter fuel lines I should have between the carbs? Also, should the fuel line between the fuel pump & bottom carb be the same diameter, or do I need an inline fuel filter to act as a join between larger diameter fuel line from pump to smaller diameter fuel line to bottom carb?

 

[Jiggz]

Re: 1990 90hp Carb Springs & Fuel line questions

Maybe you should just try 1/4" ID fuel lines since this is the next smaller line down. I know for sure my fuel lines between the fuel pump and the carb is 1/4" and I believe same is true with the fuel line between the carbs.

 

[mitchbuck]

Re: 1990 90hp Carb Springs & Fuel line questions

Thanks Jiggz! I'll get some 1/4 in and go from there...

 

[mitchbuck]

Re: 1990 90hp Carb Springs & Fuel line questions

UPDATE: Picked up some 1/4-in fuel line and tried installing it on the carbs it was too small! I had to force it on and even then they wouldn't go on all the way. So I cut some fresh pieces of 5/16 in fuel line and installed them. The leaks are mostly gone now, but I think I need to get some better clamps on them than just zip ties.

Anyways, I took the boat out for first time since rebuilding the carbs and when I tried getting up on plane the engine bogged down hard! Ugh! I had the engine running great before rebuilding the carbs.....only rebuilt them because I was having trouble with cold starts. So back to the drawing board a bit....

 

[pnwboat]

Re: 1990 90hp Carb Springs & Fuel line questions

Not uncommon for the 3 and 4 cylinder Force motors to be a little finicky with cold starts. Did you do the "link and sync" on all three carburetors after you got it all back together? There is a good explaination in the "sticky" at the beginning of the Forum under Force & Chrysler FAQ and other great information

 

[mitchbuck]

Re: 1990 90hp Carb Springs & Fuel line questions

Yup did the lynch n synch. Its either something still with that or something going on in the carbs (i hope not anything new).

 

[pnwboat]

Re: 1990 90hp Carb Springs & Fuel line questions

Replacing the gaskets shouldn't affect anything with the carbs themselves. With the motor in the normal upright running position, squeeze the primer bulb 4 or 5 times to make sure it get's firm indicating that the needle valves are working properly. Make sure the gas tank is not close to empty.

 

[Jiggz]

Re: 1990 90hp Carb Springs & Fuel line questions

When you say bogged down does the motor sound like it's running out of fuel when trying to increase rpm (go high and then go low and then high) or it just won't come up at all and stays at low constant rpm? Do you have a clear fuel filter between the fuel pump outlet and the carbs' inlet? If yes, was it full or 3/4 full when the motor bogged down? If you do not have the clear fuel filter put one in, it is an indispensable diagnostic tool for fuel related problems and costs less than $10. Just get one from WM or some autoparts, just make sure the connectors are the same size as your existing fuel hoses, which I believe is 5/16". And it doesn't have to be big or large so as not to take a lot of space in the cowling.

 

[mitchbuck]

Re: 1990 90hp Carb Springs & Fuel line questions

Update: I tested the engine again and it was still bogging down hard...when I do a hole shot the engine just couldn't make power under load trying to get up on plane. There is fresh fuel, filters, fuel lines, and spark plugs on the engine. I will take your suggestion Jiggz and get a clear filter next time.

So I ended up taking the carbs apart again just to make sure they were assembled correctly. I cleaned out the passageways with compressed air to make sure there were not any blockages. I put fresh lines on the carbs and cranked down the zip ties and now they don't leak finally! After reassembling the carbs and performing the lynch and synch yet again, I tested the boat today with the same results (bogging/can't get on plane). While on the water I adjusted the throttle cam/roller and air mixture screws with no improvement. I also tried pumping the fuel bulb, but it was solid and it didn't help. The choke has stopped working so I couldn't test it to see if it was fuel starved. I verified that the throttle plates were horizontal at wide open. So I am at a bit of a loss now and not sure where I should go next. I've got the compression gauge handy and will test next to make sure things haven't changed since last fall. This is really deflating because I had the engine running great (except for hard cold starts) before rebuilding the carbs...