Boating How-To’s - Boat works on land, stalls and wont restart in water

I was towed last night (after recently purchasing this boat). The motor started right up, we started trolling and then it just cut out. It would start right up in neutral, but would cut out when I tried to put it in forward/reverse, then when I put it back in neutral it would cut right back on.

I took it home, and it started right up in the driveway (obviously with ear muffs)!!!!!! Fired up perfectly, changed from forward/neutral/reverse with no problem, was pissing well. Everything was intact, shifting cables were fine.

Anyone have any idea? I'd appreciate any feedback. Could this be an E-10 problem? I'm putting in regular gasoline with star-tron. Should I run seafoam through it? It currently has half a tank (17.5ish gallons)

I have a 1995 Mako 171 with a 2000 Mercury 115 outboard.

Any input is greatly appreciated!

I was having pretty much the same problem with my 150 yamaha. It would idle and go into forward and reverse on the muffs..But when I put it in the water as soon I tried putting it into gear it would die. How long had the boat been sitting before you bought it? My problem was with the carbs. They had some junk in them and also needed to be adjusted. The reason it runs on muffs is because there is not as much back pressure like there is in the water. Its easy for the the engine to run its not working as hard. When you put it in the water the pressure makes the engine work more and its not getting the gas it needs. You probably need to have the carbs and fuel lines cleaned. Maybe have the carbs adjusted. There is probably some crap in there from the motor sittin or it could be coming from crap in the gas tank.

I think it was sitting for a month maybe, I'm not entirely sure. What you've said seems to be the central theme of what I believe is occuring. How do you suggest cleaning the carbs/fuel line? I dont think it's the fuel line because I pinched the fuel line hose and it still worked fine so I think the gunk is in the carbs.

If it's 'varnish build-up' in the carbs, add some SeaFoam to the fuel and run it thru.

On my little Honda 35 I sprayed Deep Creep thru the carb after removing the float bowls (3).

AFTER I cleaned out the mouse nest and replaced chewed hoses.

It's running lean. No back pressure on the exhaust in the driveway, runs fine.

Time for some carb cleaning and idle adjustment.

I decided remove the air box and spray sea foam into the carbs. The top two carbs would cause the motor to almost die out when I spray sea foam in. When I sprayed into the bottom two carbs the motor would continue running as usually then shoot a huge plume of smoke out. I used the whole can across the four carbs.

After this I took a 16 ounce can of sea foam and mixed it with 3/4 gallon of gas, and ran that through the motor for 15 minutes to go through the fuel lines.

It seems like the bottom two carbs are super clogged. I plan on running the remainder of the gas through the motor tomorrow.

Its touch to clean the crap out of the carbs while its still on the motor. You can remove the bowls and try to clean as much as possible. You will probably need to take them apart and clean the jets and everything else. Just removing the air box and spraying sea foam in isn't really doing to much. If its varnish in there you will really need to soak the parts. Just spraying them isn't enough to clean that crap off. Good luck

If I buy a carb kit, I should be able to do it on my own, no?

Do I even need to buy a carb kit, or should I just take it apart and clean the hell out of everything I see?

low compression, back pressure on exhaust? Tweak up the idle.

I didn't neet to buy a carb kit. Just take it apart and clean everything you can. Be careful not to ruin the gaskets. You might need to buy new gaskets. You should probably look in a manual for the engine and see what the carbs should be adjusted at and make sure they are correct.

Its obviously not firing on all cyls.

Do a compression test before buying any parts.

If compression is ok,

Do a spark test with a spark tester.
Set the gap to 3/8th inch and compare each cyl, I suspect one cyl will not have a blue spark.

It might be nothing more than a bad coil.

If you have good spark on all cyl's order rebuild kits and do all carbs.
http://www.youtube.com/watch?v=mjzEqbKuTXs

Carb cleaning is ok if you're stuck on the water but a proper job requires parts to be swapped out, cleaning can't fix jets with wear rings or fix old gaskets.

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Will do! Thanks for the advice!

Carb kits are normally relatively cheap but I guess 4 might set you back. They are usually a bunch of gaskets and sometimes springs.

I'd suggest taking apart your carbs one at a time, starting with the troublesome two. The gaskets holding the jets might be so bad that excess fuel is blowing past them. It's also possible the floats are compromised or the tang needs to be adjusted to shut-off fuel-flow when the bowls are full.

When removing the floats, you want the carb to be on a solid surface so you don't lose any of the itty-bitty pins, clips or springs. Trust me, they do tend to fly if you don't controll them carefully. A light shake will tell you if they have developped a leak and hold fuel and need replacement.

A shop manual is always going to come in handy but your local shop will probably print-out an exploded diagram for you if you buy a rebuild kit or float

Oh... The reason I suggested doing one at a time is in case you aren't sure where something goes you have fully assembled units to compare it to.

Good luck!

Well the boat is in the mechanics yard again. He rebuilt the carbs and ran new fuel lines. He took it for a water test, ran the hell out of it and it worked fine. 15 minutes later on the water without him and it dies again. He is rebuilding the fuel pump as he says this is the problem for sure.

The problem started out with it dying occassionally during trolling. Then it got worse and wouldnt start here and there. Then it's gone to about every 15 minutes it dies and I have to fight like hell to get it started.

I did notice if I keep pumping the primer it will keep working.

Good luck with that pump. I first rebuilt mine because I thought it was time. The new check valve membranes were little smears of nylon sheet. If you don't put them on just so, they curl up. I quickly got sick of it stalling out and re-installed the rubber ones. I have rebuilt the pump again since then and just left the antiques in place.

I hope this visit to the shop straightens things out for you.

Any updates? Always curious to the 2 stroke threads, as I own one as well. What did the shop tab set you back?

Do you have a cut out switch.
Runs great with muffs and cuts out under load, sounds like the switch needs to be adjusted to me.

Well the boat is in the mechanics yard again. He rebuilt the carbs and ran new fuel lines. He took it for a water test, ran the hell out of it and it worked fine. 15 minutes later on the water without him and it dies again. He is rebuilding the fuel pump as he says this is the problem for sure.

The problem started out with it dying occassionally during trolling. Then it got worse and wouldnt start here and there. Then it's gone to about every 15 minutes it dies and I have to fight like hell to get it started.

I did notice if I keep pumping the primer it will keep working.



If you have to prime the bulb to keep it running sounds like a hole in fuel pump diaphram?
Did the mechanic tell you spark and comp is fine?

I'd like to share my own experience, and maybe give you some ideas of your own.

My two boys bought a Valco w/ a 15HP Evinrude, ran fine at seller's parking lot.

We make a test run that eve. It's a real bugger to start. Soon as I back off the choke, it wants to die out. Not wanting to face the disappointment I would see in there eyes, I throttle, get it in gear, and get under way. Once at that point, we could idle w/ choke pushed in. Got to harbor entrance, just so we could throttle up. It throttled well, and let me decide it was way too much motor on that boat to let boys take outside harbor. The thing could indo with a little unfortunate judgement.

Back at shop, I go online to find some pointers w/ the outboard. Frustrated, I just go to air, fuel, spark concept. I have no experience with outboards. I did take apart the fuel pump before I figured out it was a vacuum leak. People tend to over-tighten the plastic cover on the top of the carb, I found a long crack on the top, with no crack visible on bottom. The lid is obsolete, a compatible replacement has an extra screw to secure the lid. The carb would need to be tapped, or replaced altogether. The carb otherwise looked very clean. The was a screw hole from the choke bracket, right in the throat of the carb (but usually filled by screw anyways) I actually teflon threaded the bolt, and mar-glassed the top of the lid. I felt, like, what the hell.. I even made an elongated washer to press down where the replacement had added the screw.

Now, it would start up first pull, no choke needed. We get it in the water, and ran perfect all day fishing in harbor. I tried to throttle up at harbor entrance, and it would just bog down. The bird in the back of my head said it was unlikely an all new problem developed coincidently, but I felt confident I licked the last problem w/ the choke. It started up just fine. I pulled the lower plug wire while idling, and the rpm just came down a little bit. The little jolts remind me of grandpa's practical jokes in the backyard (motor city). When i tried the top plug, the engine just quit. I had already sanded the plugs, and they still didn't look to bad. I replaced the lower coil for $20. It made an improvement, it came up from idle while, in gear, a little more, but would still bog when trying to apply any load. I installed the fuel pump repair kit, the old rubber was worn, the first time I just re-assembled it. A little improvement, but not it. I started thinking I needed a new $100 power pack, at least new plugs. While putting back to the ramp this afternoon, i got an idea, and lifted the lid. I put my hand over the air intake, the idle came right up. I could even throttle it heavy, like it was back to normal.

lol, I stuffed some crumpled paper into the air intake, it runs like a dream now. ;)

btw- during that process, I could get it to throttle at the dock in gear, tied off, but not under way in a breeze, where the engine got more air.

I suppose I'll get that newer model carb lid, and tap the carb. ...eventually