1997 75 hp carb adjust question

[danb303]

I've been having problem this year with my carb (I think). It's a long story but the short version is that my bulb had a hole in it and I ran it 2 weekends without one. No problems other than the motor didn't want to take the throttle from an idle.
I replace the bulb and all hell brakes loose.LOL Anyway, now it don't want to idle (idles ok for a few seconds then dies), it's hard to start, and it doesn't want to run at WOT (runs better when I back it off just a bit.

I am new to baots and sure could use some advise.

Might should also add that it has fouled the plugs during all this. I replaced the plugs and it ran like a champ in the driveway (muffs on) put it in the water and all this started.

 

[TwoFish]

Re: 1997 75 hp carb adjust question

Did you set the float height and retune the engine?

 

[danb303]

Re: 1997 75 hp carb adjust question

No I have't done either. I have read how to set the float height but I don't know how to tune it. I have built and tuned many Holley carbs for myself and friends but I have never touched a boat carb. This is my first boat.

 

[TwoFish]

Re: 1997 75 hp carb adjust question

Luckily these motors are fairly simple to work on so if you have some mechanical knowledge you should be OK. If you plan to work on the motor yourself a workshop manual is a must. Don?t ever run the motor with a lean mixture. Always ground the sparkplug leads if you remove them from the plugs to prevent damaging your coils.


A ?Sticky? at the top of the Force forum has info specific to Force /Crysler. http://forums.iboats.com/showthread.php?t=449011


Frank Acampora has written a great article about tuning these motors. Located as a ?Sticky? at the top of the Force forum.
http://forums.iboats.com/showthread.php?t=431021
I have a 1998/ 75 hp. I used the settings from my manual and the procedure from Frank?s thread and it worked well. His description is MUCH better than what is in the manual!


The ?Engine repair & Maintenance? section of the Iboats forum lots of good topics including carby cleaning. http://forums.iboats.com/forumdisplay.php?f=4

Youtube has some info there on outboards as well.

Take the time to read up on what you want to do first and if you are not sure this forum has some great people who have helped me learn to work on my motor. I would not have had the confidence to do it without them.


Good Luck

 

[danb303]

Re: 1997 75 hp carb adjust question

I finally carried it to the lake and tuned the carb as directed in the other post. It runs tons better but still isn't perfect. I am hoping that the reason is my one way check valve is bad. The bulb kept getting soft. I was able to pump it up a couple times but after that it was leaking too bad to get it tight. When I turned the engine off I heard it bubbling in the tank. I'm going to upgrade to a larger tank and a newer style valve and hopefully that will cure my problems. which are....

1. Idles for a few seconds then it tries to die.
2.At WOT I can feel it bogging down just a very little bit. I hope it's sucking air and the new valve will fix that.

any thoughts?

 

[TwoFish]

Re: 1997 75 hp carb adjust question

It sounds like it is not getting enough fuel, be it air getting in, not pumping fuel well or a blocked get in the carby. It is a good idea to fit a fuel pump kit to the fuel pump if it has not had one recently. They are relatively cheap and easy to fit. There is usually an inline fuel filter between the fuel pump and the carby. Replacing this is part of a standard service and will eliminate another potential fuel blockage.

If you suspect the motor is running lean you need to get it sorted as this can damage the engine. All the lubrication for the motor comes through the fuel. If you are low on fuel you are also low on lubrication for the motor.

I had trouble with my motor stalling at idle. I finally found the problem was an incorrectly run breather hose on the in floor fuel tank.

Good Luck

 

[danb303]

Re: 1997 75 hp carb adjust question

I'm going today or tomorrow and getting a new tank, the newer style quick connect and a new hose kit. They sell all that a Academy Outdoors. My fuel line has 2 different types of quick connects on it. The one near the motor has the old metal insert twist type and the one near the tank is an in line type with the release lever on it. Mine doesn't have the quick connect on the tank.

If I replace all that can I do away with having 2 quick connects? Can I just have one at the tank and not one at the motor? THe line isn't a problem to take off of the pump.

Thanks for any info

 

[TwoFish]

Re: 1997 75 hp carb adjust question

My motor only has one connector at the tank. The fuel line is one piece from that connector to the fuel pump.

 

[danb303]

Re: 1997 75 hp carb adjust question

Great...thanks

 

[danb303]

Re: 1997 75 hp carb adjust question

I hate to bring this back up but I finally had a chance to try the boat out. It cranks and runs real good with the muffs on but putting it in the lake it's a different story.
After the problem mentioned above I installed a new tank, quick connect, line, bulb, and filter. With all this new I still can't get the bulb to pump up tight.

In the lake it cranks fine but doesn't want to idle past 10-15 seconds and it dies.

It also don't want to take the throttle unless I pretty much shove it all the way. If I slowly engage the throttle it dies.

At WOT it seems to have a little mis and it will only run 16 mph (20ft pontoon) I tried backing the screw out 1/4 turn and it seemed better for a minute then it was hard to tell. So I backed it out another 1/4 turn and it did about the same.

Thanks for any help

 

[TwoFish]

Re: 1997 75 hp carb adjust question

Could be a few things.

Fuel pump may not be suppling enough fuel. Have you tried to pump the fuel bulb at idle to see if this helps. Under normal use the fuel bulb with not stay hard as fuel in the hose is under a slight vacuum but should not be sucked flat either. As mentioned earlier you may need to rebuild the fuel pump.

If the bulb with not harden up when priming it you may have air getting in the line, a leak in the line or the needle, seats in the carbs may not be sealing properly or incorrectly set float height.

The other thing that can cause an engine to die at idle is that the idle speed is set too low. It should be 700 ? 750 rpm with the boat tied to the dock in the water and the motor in forward gear. This will be about 1000 rps in neutral. At slower speeds the fuel pump does not get enough back pressure to pump fuel properly. Refer to the link above in tuning. Frank?s tuning instructions are very good.

Good luck

 

[danb303]

Re: 1997 75 hp carb adjust question

A local Marine store has me a fuel pump kit ordered. I'm going to try that.

Also, when I pump the bulb it sounds like air going back into the tank. I was thinking it wasn't supposed to do that.???

Does that card have a low end circuit and a top end circuit? If so could the low end be somwhow blocked?

THANKS

 

[danb303]

Re: 1997 75 hp carb adjust question

One more?

Can you check the fuel pressure? I have an inline gauge that I can use.

 

[TwoFish]

Re: 1997 75 hp carb adjust question

Yes the carby has a slow speed and a high speed circuit. The mixture screw adjusts the slow speed circuit. The high speed jet is not adjustable. The slow seepd circuit works to about 2000 rpm and the high speed starts working from there. Both circuits feel fuel in a WOT but the slow seed circuit has less effect.

There is a thread in the FAQ section of the forum on testing fuel systems. http://forums.iboats.com/showthread.php?t=283363

 

[danb303]

Re: 1997 75 hp carb adjust question

I checked an exploded view of my carb on the internet and it looks like there is a main jet (high speed?) and a throttle jet (low speed?)
I'm not sure I know how to get to the throttle jet. I am about to go out to the shop and check it out.

Also, I have a small hole in the side of the carb that goes thru to the inside. Is that some sort of air bleed or am I missing something.

And by the looks of the plugs I am running lean

 

[TwoFish]

Re: 1997 75 hp carb adjust question

It does sound like it is running lean.

See what happens when you fit the fuel pump kit.

There is a section on carby cleaning in the FAQ I mentioned earlier.

I had a look on my carby for holes. There are three but they are all blocked off. Two shallow ones on the starboard side and a deeper one (1 inch deep) on the port side.

Have you checked the compression to see if it is OK?

 

[danb303]

Re: 1997 75 hp carb adjust question

The compression on all 3 cyl is right at 120. real close to 118-122 hard to tell on my Craftsman gauge.

I sprayed card cleaner in that hole and it came out inside the carb. That is what concerned me. I'll try to post a pic tomorrow.

I cleaned the carb again and put it back on. First thing I noticed after putting it back on was that it was idled high (I had been idling it up to see if it would idle) That kinda makes me think I might have made it better. Also noticed lots more smoke coming out the exhaust which hopefully means it's getting more gas. I'm going to try to take it over to the lake and try it out tomorrow evening. My fingers are crossed

Thanks for the help

 

[danb303]

Re: 1997 75 hp carb adjust question

oh and... I teed in a vacuum gauge to the fuel line before the pump and it didn't show any vacuum (on the muffs)

On the carb... running the screw in makes it more lean or richer?

 

[TwoFish]

Re: 1997 75 hp carb adjust question

Has the fuel pump kit arrived? I would be reluctant to run the motor hard if you think it is not getting enough fuel because of the pump. All the lubrication for the motor is in the fuel. If you are low on fuel you are also lower on lubrication.

I?d be interested to see a photo of the carby.

Turning the screw clockwise (IN) leans the mixture and anti clockwire(OUT) makes it richer. As mentioned in the tuning post don?t run the motor with the screw any less than ? of a turn from fully closed.

 

[danb303]

Re: 1997 75 hp carb adjust question

I don't think I am properly adjusting the idle. I have been using the rod with 2 eyelets on each end to adjust it. Seems like I remember reading that someone was saying that was not correct.