'98 75hp fuel issues (amongst other things)

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CatTracker1860

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Jun 3, 2019
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New guy to the forum. Please forgive me if I reittreit any issues or questions that have been answered in previous posts as I have searched the forum repeatedly for any issues or questions I've had previously and have always found answers. I figured it was time to join as I endeavor on fixing the fuel issue in my outboard. I'm not extremely familiar with working on outboards so don't beat me up too bad.

I checked compression before buying the boat and it was 125 on all 3 cylinders

​​Ive had the boat out 3 times.
I've been dealing with replacing fuel lines/filter and cleaning the carb after having trouble getting the motor to start on the water several times. Once started it was "spotty" on running with some skipping and cutting back. After pulling it out and replacing the filter and fuel lines I cleaned the three plugs which looked pretty decent. Put it back together and started it in the yard and it ran great other than it seemed to idle very low, so I adjusted the screw on top of the carb thinking it was a idle screw (not sure that was a good idea now). Would crank with one flip of the switch. Took it to the lake and rode around for an hour at speeds between fast idling and wide open. It cut off and got hard to start. I could lift the high throttle lever and it would fire up and run rough, smoke bad. When I put the lever down it cut off. I finally got it loaded up and back home. Pulled the plugs and Top plug was wet with mixed gas, Second plug was black as was the Third. I cleaned everything but haven't started it yet due to wanting to pick brains on here.
 
jerryjerry05

jerryjerry05

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(so I adjusted the screw on top of the carb thinking it was a idle screw (not sure that was a good idea now).

Your right BAD idea.
That's the air/fuel mix screw for running at idle.
When adjusting anything on an outboard, try to remember the original setting so it can be returned.
Set air screw: 1 1/2 turn out.
Then in the water , in gear adjust in 1/8th turn waiting 10 seconds between turns.
When it stutters, coughs, stalls then turn back out 1/2 turn.

(It cut off and got hard to start.)
Sounds like it got hot???
Test the alarm system and see if the warning horn is working.
New to you, change the impeller(even if the seller says it was just changed)
Some people LIE!!!
There's a temp sensor on the block, key on, ground the sensor.
That should make the alarm/buzzer sound off.
Most buzzers are small and hard to hear when the motor's running.
I replace with a car or motorcycle horn.
If you do that? it can be wired backwards and not sound off.

Before you do anything more, read the first 4 posts in this forum.
Some may pertain to your motor a lot won't.

The setting of the air screw should be in there somewhere.
Also u-tube video's are a good bet for some repairs.

Also "NO SUCH THING AS A DUMB QUESTION"​
 
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CatTracker1860

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Jun 3, 2019
Messages
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Jerry, after reading further in this forum I realized I screwed up for sure. Since I made that screw adjustment at home before taking it to the lake I feel like that may have been the culprit to it cutting off like it did. Reason being is it cut off while idling to the dock and it had done this a couple times prior while going under the few bridges also. When I say it was hard to start I mean it would only crank with the throttle lever lifted nearly wide open and would cut off if I put it back down. I think after having to run at low RPMs for an extended period of time due to boat traffic and rough waters didn't help plug matters either. But after pulling the plugs the top plug is wet with fuel, the mid and bottom were both black and nasty.

I ran this boat last weekend and had the issue with having to crack the throttle slightly to crank it but once it fired up it ran ok. I could idle it and shift without it cutting off.
 
jerryjerry05

jerryjerry05

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Reset and go for a ride.
What are the rpm's at idle, in gear, in the water?
750-800 is recommended.
 
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CatTracker1860

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Jun 3, 2019
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Jerry, I'm not sure of the RPMs as I do not have a tach. I don't run it hard since I don't have one and am afraid of running high RPMs for too long. I'm going to reset the screw now. Unfortunately the lake is a 40 minute ride, is a bucket test ok for checking that?
thanks
 
F

foodfisher

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Feb 18, 2009
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I'd get a tach no matter what. It will make adjustments so much easier and forewarn you of coming problems.
 
jerryjerry05

jerryjerry05

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May 7, 2008
Messages
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The tach wire should already be in the harness.

Yes you can use a hose or DEEP bucket.
The cavitation plate needs to be at least 3-4in over the plate.

Set at 1 1/2 turn out and reset when you get in the water.

They sell an item called "Tiny Tach"
Just wrap the wire around the plug wire.
Make sure it's for an outboard.
 
jerryjerry05

jerryjerry05

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If you get a TT make sure the battery's replaceable.
I bought the first TT when they came out.
No replaceable battery :( after a few years it DIED :noidea:
 
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CatTracker1860

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Joined
Jun 3, 2019
Messages
6
I cleaned my dirty plugs, cleaned my fuel filter out, cleaned up a few things with the fuel system and reset that mixture screw. Bumped the switch and she was purring! Can't wait to get it on the water and fine tune it.

Thanks all for the help. I'll get a tach next week and try to locate the wire in the harness for it to get it hooked up 🤙
 
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