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9.9hp Mariner issues

H

heckhole

Member
I have a 1989-ish Mariner 9.9hp with a few issues.

I've had it for roughly 8 years now and just recently started experiencing issues.

First the engine started to start hard, took a lot of pulls or a shot of starter fluid. Sometimes it would bog and die out, once it would run - it would rev up nice and push the boat well then start to lay down and run at about 3/4 throttle and down on power. I started to poke around and noticed the enricher leaking. Replaced the enricher, solved the fuel leak but did not solve my running problems - at all.

So I treated the fuel and stuck with using my trolling motor until I had sufficient funds to fix the engine.

Took the boat out of storage this year and not to my surprise, it runs the same. I pulled the plugs & the top plug was bone dry, but brown. The bottom plug was brown and barely wet. I let the plugs dry, swapped them and the boat didn't run differently. When I pulled the plugs this time, the top plug was slightly wet, the same as the bottom plug now.

So I swapped coil packs side to side, checked the plug wires, everything looks good.

Started it up, idled okay but it still does the intermittent sucking sound and sounds like a major miss every once in a while, when I put it in gear and give it throttle, it sometimes bogs or makes the sucking sound, almost shuts off and then comes back to life.

I've noticed when pulling the plugs, the top plug is significantly warmer than the bottom plug. The bottom plug doesn't feel warm at all sometimes.

Not sure what to do...any advice?
 
Check the intensity of spark !--------The ignition system was engineered and built ( at some expense ) to be able to jump a gap of 7/16" or more.---Let us know how good the spark is.--------Check compression too and report the results.
 
racerone said:
Check the intensity of spark !--------The ignition system was engineered and built ( at some expense ) to be able to jump a gap of 7/16" or more.---Let us know how good the spark is.--------Check compression too and report the results.
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My compression gauge will not work in this engine, but I can tell you the good'ol thumb in the hole compression is excellent.

As for spark intensity, if I pull the plugs and pull the cord, the spark jumps well, but that really doesn't mean too much, right?
 
Laying plugs on the block is a meaninglessw test !!---Compression gauges are a good investment at less than 1/2 hr labour at many repair shops.
 
Understood.

I pulled the carb apart, no clogs everything was spotless. Replaced vacuum lines just for ****sngiggles.


She still runs when she wants, however It did run on one cyl for a while, shut it off and it fired back up on 2 cyl and ran fine. Put it in gear and it ran well. Shut it off and tried again, ran on 1 cyl and died whenever I touched throttle.
 
Open the idle mixture screw (CCW) one half turn and see if that helps.

Jeff

PS: I've recently run into a LOT of bad coils on these motors.
 
fastjeff said:
Open the idle mixture screw (CCW) one half turn and see if that helps.

Jeff

PS: I've recently run into a LOT of bad coils on these motors.
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I did move the coils and I couldn't get the cold plug to follow any coil. The colder plug was always on the bottom.

At one point I had it idling for about 5 minutes, with some smooth idling and then periods of misfiring etc. When I shut it down, the top plug was nice and hot, bottom plug was easily 15 degrees cooler & always felt to be the same temperature as the air outside.

I did change a coil around 4 years ago.

I sprayed around the carb checking for leaks with carb cleaner, it didn't rev up, so I eliminated any air leaks. However, I did notice when it does the large sputter, I see & hear a poof from below the vacuum line area on the right side (looking at the motor while on the boat). When it does that, it doesn't fire at all for a moment and then poofs & comes back to life.
 
fastjeff said:
Try opening the idle mixture screw (hiding behind a black plastic plug) about 1/2 turn CCW.

Jeff
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So... It took about 20 pulls without using starter fluid to get even a half chug out of the boat. I gave it a shot of starter fluid and it idled, chugged, popped and smoothed out a little, died as soon as I shifted it into gear.

Turned the idle mixture screw a half turn counter clockwise, idle smoothed out almost instantly and shifts into gear and runs great in the bucket. Starts first pull.

Are ya freakin' kidding me?? Both plugs are equally warm now too.
 
fastjeff said:
Good work!

Jeff

PS: Thank the enviro-whackos and agri-busiiness for ethanol gas, which is what causes this.
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It's really the ethanol??

I was shocked that the 1/2 turn literally flipped a switch and made it run like it USED to. It runs well in the bucket... hopefully today I will get a chance to put it on the lake and see how it runs actually pushing the boat.
 
Yeah. It has less energy per gallon than pure gas, so you need to add more of it to produce the same result.

Jeff
 
This has been very interesting and shows how helpful the experts on this site can be. I know I've been helped here a bunch. Great job!

Steve
 
Put the boat on the water last night, I reset the idle screw and it wouldn't start. Turned it 1/2 turn CCW per Jeff's instructions and it fired up, idled great, pushed the boat well from idle to 3/4 throttle.

Any time I tried to go beyond 3/4 throttle, it would lay down or heavily bog and almost shut off. I could back off the throttle to 3/4 and it would come right back to life. Runs exceptionally well from idle to 3/4 throttle.

Any ideas? It seems like it needs some fine tuning for 3/4+ throttle?
 
Restriction in fuel line? I had a fuel hose one time that had flattened out, that was the problem. Got enough gas to run fine, but not wide open.

Steve
 
Since you mention that, I did notice the fuel line going into the fuel filter is a little twisted and collapsed. I will go ahead and replace it
 
Well, had a lot of issues with the motor today.

Started easy, only a few pulls. Idled up well, shifted into gear, took off almost got to plane and it sounded like it was running on 1 cylinder or getting too much air. If I shift back to neutral, it comes back to life and sounds healthy.


Now I messed around with it a little on the water. When it's running poorly, if I move extremely slow, I see an oil/gas slick. If I flip back to neutral, the slick goes away as the engine idles and comes back to life.
 
Sounds like the carb is flooding, or maybe there's a tear in the fuel pump gasket. One other malady of those engines is a leak at the reed valve; one side of the thing goes to one cylinder, the other side to the other. If the rubber seal around the reed valve is leaking it will cause all kinds a weird behavior.

Jeff
 
It looks like this engine has never been opened. My godfather bought it new, I inherited at 8 years ago.... I've tried spraying everything with carb cleaner while running to see if I could get an RPM fluctuation but I get no response.

I feel like something is out of sync. Forgive me for not knowing what the parts are called, but I see the throttle cable and the arm it moves. There is the white arm this piece pushes up to open the butterfly on the carb. If I put the engine in gear and ignore my throttle shaft and use the throttle assembly on the engine, it runs.
 
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Now, I'm no professional spark plug reader. Any opinions?

The plug on the left is from the bottom cylinder. It looks like it is not firing well, the strap is not a light brownish like the right (top plug).
 
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Fired up first pull in the bucket. Idles good, shift into gear and it goes to wide open throttle without a burp. Comes back down to idle without skipping a beat.

?????????
 
It must be fuel related. I held a 2x4 behind the prop in my bucket and was able to significantly bog the engine. I think a full carb kit is needed, with fuel pump.
 
heckhole said:
It must be fuel related. I held a 2x4 behind the prop in my bucket and was able to significantly bog the engine. I think a full carb kit is needed, with fuel pump.
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So, I'm looking at fuel pump kits every where...all obsolete & unavailable? Is it not common for these to break?
 
Ethanol tends to eat 'em up. You shouldn't ave trouble getting parts for a motor that new. This site has them.

Jeff
 
This should be a yamaha rebadged as a mariner import, get the fuel pump diaphragms on the yammy side. You should only have a single coil with 2 spark wires These wont run worth a crap if t-stat is missing or stuck open..
 
fastjeff said:
Ethanol tends to eat 'em up. You shouldn't ave trouble getting parts for a motor that new. This site has them.

Jeff
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I see a repair kit now. I was too stressed out to look closer the first time I searched for parts. :D

Fazt, I'm not sure about this being a re-badged Yamaha. It definitely has 2 coils.
 
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