Calling All Boat Mechanic/ Armchair Mechanics Motor Problems

[701FishSlayer]

Alright guys, since we're all experts here there's simply no need to go elsewhere for answers. Got a buddy that has just acquired a new fishing rig (was a member of FBO not sure if he's here yet, either way he will be here. The boat has been sitting for the last 3 years, he has put new plugs in it, gas etc, even went the extra mile to slap a new prop on it. That's the back story on the boat. It's an older lund with an early 80's 50 horse Merc on it. The trusty tried true and blue style. Just trying to get him out on the water but we've got some problems. After a minor tune up and good cleanup at home he slapped the muffs on it and got er running. It was fireworks, it was time to go fishing. Here's where the problem is (hope your still reading). It starts fine at home with the muffs, get er down to the lake and back er in, nope, no go. We're ballin on a budget here guys, mechanics want way too much $ for labor. I know somebody here has some input. What ya thinking? Took it to the lake 3 times today, Audobon for the first trip with the first round of bad news, got er home and running, then ran to darling and backed her down, nope. Tried one last time, ran fine at home with the muffs once again, back up to darling, nope. Die hard fisherman, just trying to get the lines wet but not experienced with boat motors. Let the guessing games begin.

 

[Vollmer]

1st thing I always used to check on my old boat was the ball primer.

 

[DirtyMike]

Does it sputter, turn over at all? Check your fuel line/filter.

 

[Chris Skager]

It runs perfect hooked up to the garden hose....

 

[Kurtr]

Does it just turn over and not.fire.when at the boat ramp

 

[Petras]

does it just turn over when ur trying it at the lake?
does it act like it's trying to fire at all?
Check and make sure the Primer ball is pumped up fairly hard. might not be a bad idea to change the fuel filter... also, just out of pure precaution I would go ahead and replace the water impeller in the lower unit... if it hasn't been run in 3 years that impeller may be dried up and cracked and not pumping water up to the motor and this can cause big problems...
biggest thing I would check is make sure your fuel line connections are tight and make sure that the primer ball is nice and firm.

- - - Updated - - -

also, is it a pull start? or does it have a key and starter? if it has a key and starter then it's likely there is a "kill switch" on it.... you could check this and wiggle it around to make sure it's not keeping the motor from making spark...

 

[drivenmarine.net]

Being it will run at home and not backed into the water, leads me to believe it has something to do with the angle of the boat at the ramp. Dumb question, but how much gas is in the tank? Could have something to do with the fuel connection on the motor. Make sure to pump the primer ball as well.

 

[Biggoose]

Been through numerous boats and motors, one tip I always do is to have the motor trimmed all the way down when starting, not sure why but had a couple older merc's that wouldn't start otherwise.

 

[Joe]

Usually a symptom of a really dirty carb. I would first double check the compression, just to find out if the motor is worth servicing. Then maybe try a Seafoam treatment, before having to go through the pain in the ass procedure of rebuilding the carbs.

 

[Bacon]

Probably don't have to rebuild carbs, but you should clean the jets. I'm guessing they are partially pluged from old gas sitting in the float bowls. Unless they were drained when put away.

 

[Davey Crockett]

If it runs so good at home but won't start at the lake pay close attention to what Biggoose mentioned about motor tilt. They are hard to get fire in the hole when trimmed up and might dump too much gas in the hole if your at an angle on the boat ramp.. When you pull the plugs when it won't start are they dry or wet ? I run one of these blue 50 HP mercs in a 16' lund, very good motor for trolling and still gets me across the lake at a pretty good clip. If it runs at home it should run at the lake.

 

[NodakBuckeye]

Pretty much covered what I know to check. My first though was trim at the ramp, they have a sensor/switch that keeps them from starting if trimmed up to much. Would be helpful to describe what exactly is happening at ramp. Good luck, it can be very frustrating! My 2002 75 sat for 6 years until I fired it up last year. Changed plugs, impeller, lower unit oil, thermostat, fuel filter, exterior fuel line and primer bulb, drained old gas and ran some sea foam through on the first tank.

 

[Radar13]

I agree with the boat trim,I had this before also

 

[701FishSlayer]

If a person had to rebuild the carbs, how nasty of a job we talking? Little youtube and a 6er get er done or should a mechanic do it.

 

[Vollmer]

If it runs fine hooked to water, I would not make a bad carb my 1st guess. But still a possibility.

 

[eyexer]

low speed jets are plugged. When your on the driveway it will start and run off just the main jet because it's sitting relatively flat. When you have it trimmed up on the water it won't start because your dumping enough fluid out of the carb overflow tube to now allow the main jet to pull fuel. and the low speed jets are plugged so they aren't helping any. Pull the carbs. remove the bowl. Remove the float and float needle. Remove the main jet and pilot jets. Remove all other jets in the carb. Then take these parts and soak them in a gallon can of carb cleaner overnight. You can soak the whole carb if you remove any rubber and gaskets. I usually soak it all but it has to be disassembled. Then after soaking blow out all jets with a can of carb cleaner using the red straw on the can.

 

[NodakBuckeye]

Agree.... What does it do at the ramp? Are there any seals on the exhaust system that could fail and let water in a interfere with starting?

 

[SupressYourself]

I had an '83 50 horse Merc. I had so much carb trouble that I now run an EFI and will never buy another carbureted motor. I had those two carbs off so many times that I could do it blindfolded.
Anyway... like others said, if it runs fine at home, I doubt the carbs are "bad". They may be a little dirty, which may be contributing to your problem, but may not be the main problem. Sometimes when the motor is trimmed up, the needle sticks in the seat and you can't get any gas out of the bowl and into the intake.
When you have it sitting flat in the lake with the motor trimmed all the way down, squeeze the bulb till it's hard and then give it a good "gorilla stomp" to make sure the needles are pushed out of the seats. Squirt some starting fluid in each carb for good measure, and then let er rip.
If that doesn't work, we will need a more detailed description of EXACTLY what it does when it's on the lake (aside from not start).

 

[Davey Crockett]

My 1982 sat in a quonset and never got used from 1984 untill I bought it in 2010, I poured a can of sea foam in a quart of mixed gas and let it run with the muffs for a good 45 minutes. Put new fuel, and a new impeller and haven't had to look at it. Knock on wood.

my last run of the year I take the gas line off and run it out of fuel before I store it. I should use stabil but I don't

 

[NDwalleyes]

I had a similar situation years ago. The motor ran different depending on the trim of the motor. If it was trimmed all the way down it ran fine and if it was trimmed up say 10% it would run rough at idle and would stall out under any load. Ended up being a crack/worn spot in the fuel line. As the motor was trimmed up the crack would open up and allow the motor to suck enough air it would stall out. If you have the motor trimmed up at the ram and trimmed down at home with the muffs on it, this could be the issue. Check your fuel line in the area where it connects to your motor or around the primer bulb.