Early 80's Mariner Experts, Need Help With 30Hp.

[ChrisAW]

I bought a Mariner 30hp for the 15'7" Smokercraft I bought this winter. Having problems with gettimg it to run properly. Ran alright when checking it out but after getting it in the water it doesn't have any power, won't run full rpms and wants to sputter and cut out. Plugs are black and are coming out wet.

Has good compression, 130psi. Cleaned carb, but am having problems with making sure its tuned correctly, as I'm not familiar with them.

So far, we have checked the fuel pump and it had one of the metal leaves or whatever bent out, so fixed that. No leaks. The reeds are in very good shape, look freshly replaced. Has spark, but hard to say if its weak or not. Float is not taking on fuel/is air tight.

I could used some help with the carb though. Not sure how the float should be adjusted. Usually level when resting right? Well when I did that it wouldn't start at all without starting fluid. Adjusting it so it would be resting below level, it is getting fuel again and starting but running like poop. Acting the same and plugs are still coming out wet\black. I plan on replacing the needle/seat, but I have a feeling that's not the only issue here. I did read someone had a problem with a blockage in the exhaust port. So I plan oon checking that out as well.

Just looking for more info or any suggestions as to what else could be the problem here.

I'm getting depressed, season starts on Saturday here and my boat isn't going to be ready

[Goaltender]

If you're loosing power under load it is usually one of two things. First - the carb could be starved for oxygen. Take the cover off and try running it with it off and see what happens. Second, you have a bad coil.

[ChrisAW]

If you're loosing power under load it is usually one of two things. First - the carb could be starved for oxygen. Take the cover off and try running it with it off and see what happens. Second, you have a bad coil.

 

I have ran it without the cover, doesn't do much. I could see the coil being a problem, but not sure how I could test it to be sure. It has spark, but it could be a weak. Any tips?

[Goaltender]

Under load the coil will not produce enough spark to keep the engine running at higher speeds. This may be of help... Good Luck!

 

[ChrisAW]

Well one of the first things that my buddy mentioned was that the crankcase seal on top could be going bad, but he had seen no sign of it. Until I just called him telling him that it basically tried to blow itself up, and was revving on its own. Apparenly this is a definite sign of a bad seal, so I guess we get to break it down and really get to work on this thing.

[james 14]

Well one of the first things that my buddy mentioned was that the crankcase seal on top could be going bad, but he had seen no sign of it. Until I just called him telling him that it basically tried to blow itself up, and was revving on its own. Apparenly this is a definite sign of a bad seal, so I guess we get to break it down and really get to work on this thing.

 

Did you clean the carb before or after you started having problems?

 

When you say "blow itself up" and "revving on it's own" are you saying that it all of a sudden ran up to a high RPM? Did it stay at the high RPM?

 

I had a carb issue with an early 80's Yammie (which I think is similar to the Mariner) where the float was sticking due to debris in the bowl. It would rev up like this to where you thought the thing was about to blow until you hit the kill switch...even then it took a few seconds to get it to shut down.

 

I also had issues with setting the float height. In my experience it takes VERY little movement to make a big difference. About 1/8" was the difference between the engine not even starting and running perfectly.

 

What you're describing with the wet plugs and inability to run under load sounds like the engine is getting flooded. It's either dumping too much fuel in or it's air supply is getting choked out somehow.

 

Did you adjust the air/fuel mixture? There's a little screw on the side of the carb (not to be confused with the little screw adjusting throttle position at idle). This screw adjust the air flow into the carb to make the motor run rich or lean.

 

Did you check the spark plug gap?

 

Are you sure you cleaned the entire carb? Try spraying some carb cleaner through the intake while the engine is idling. Don't do too much at one spray or it'll stall and flood. Hit the throttle simultaneously with each spray. If it seems to help you'll need to pull it apart again and make sure everything is clean. There are a lot of little holes that the air travels through.

 

You may also want to check your butterfly valve to make sure it's opening as you push the throttle. This is another setting that could be out of whack where the valve is staying shut too long. Ideally, it'll be perfectly level at WOT.

 

Maybe even play with the idle RPMs. If it's idling too low it could be flooding when you give it gas if you push the throttle too quickly.

 

I'm trying to give you all of the easier possibilities since 95% of the time it's something like this. I would start with the air/fuel mixture screw. If that doesn't work adjust the bowl height in smaller increments. Start out with it too lean and gradually increase from there. Once it gets enough gas if it still wants to choke out the play with the air/fuel mixture a little more. If it doesn't work set that screw at a medium level and check the butterfly valve and idle RPMs. If that doesn't work spray the carb cleaner into the intake while hitting the throttle. If that doesn't work check the spark gap (should probably do that anyways). If none of that works I got nothing for you.

[Nitrofreak]

One more thing to check is the keyway for the flywheel, make sure the key is not worn allowing the timing to be off.

[ChrisAW]

Did you clean the carb before or after you started having problems?

 

When you say "blow itself up" and "revving on it's own" are you saying that it all of a sudden ran up to a high RPM? Did it stay at the high RPM?

 

I had a carb issue with an early 80's Yammie (which I think is similar to the Mariner) where the float was sticking due to debris in the bowl. It would rev up like this to where you thought the thing was about to blow until you hit the kill switch...even then it took a few seconds to get it to shut down.

 

I also had issues with setting the float height. In my experience it takes VERY little movement to make a big difference. About 1/8" was the difference between the engine not even starting and running perfectly.

 

What you're describing with the wet plugs and inability to run under load sounds like the engine is getting flooded. It's either dumping too much fuel in or it's air supply is getting choked out somehow.

 

Did you adjust the air/fuel mixture? There's a little screw on the side of the carb (not to be confused with the little screw adjusting throttle position at idle). This screw adjust the air flow into the carb to make the motor run rich or lean.

 

Did you check the spark plug gap?

 

Are you sure you cleaned the entire carb? Try spraying some carb cleaner through the intake while the engine is idling. Don't do too much at one spray or it'll stall and flood. Hit the throttle simultaneously with each spray. If it seems to help you'll need to pull it apart again and make sure everything is clean. There are a lot of little holes that the air travels through.

 

You may also want to check your butterfly valve to make sure it's opening as you push the throttle. This is another setting that could be out of whack where the valve is staying shut too long. Ideally, it'll be perfectly level at WOT.

 

Maybe even play with the idle RPMs. If it's idling too low it could be flooding when you give it gas if you push the throttle too quickly.

 

I'm trying to give you all of the easier possibilities since 95% of the time it's something like this. I would start with the air/fuel mixture screw. If that doesn't work adjust the bowl height in smaller increments. Start out with it too lean and gradually increase from there. Once it gets enough gas if it still wants to choke out the play with the air/fuel mixture a little more. If it doesn't work set that screw at a medium level and check the butterfly valve and idle RPMs. If that doesn't work spray the carb cleaner into the intake while hitting the throttle. If that doesn't work check the spark gap (should probably do that anyways). If none of that works I got nothing for you.

 

 

I did pretty much everything you said in your post. Another sign that I didn't mention is that when its backfiring, I can see smoke or air movement coming out from under the flywheel, as well as small amounts on gas/oil leaking from the top of the crankcase.

 

It did pretty much exactly what you're describing about how it revved on its own. What was the cause of this you think? I know a couple people that I described this too and mentioning the backfiring, smoke from under the flywheel and the gas/oil, they said the same thing. Seal is bad on top. But I was playing with the carb and the float a lot, so I could have done something there for sure. Last adjustment I had made was trying to help keep it from completely swamping itself, I made the float shut the inlet valve completely when level. The plugs were coming out dry now, but still black/suity.

 

Edit: And I was able to get it to run better from this. It will rev under a load now, and was idling/running without stalling. It just kept backfiring no matter what I adjusted. The backfiring would stop if I gave it any throttle for the most part as well.