1984 Mercury 90 Starting Problems

[ktEOS]

Hello all!

I'm new to the forums, so please forgive me if there is a thread similar here that I haven't seen.

My husband and I just bought a 1984 Boston Whaler 17' Newport. It has been sitting in a barn for questionable amount of years and, of course, hasn't been started either (the registration expired about 9 years ago, so we're guessing that's how long it's been sitting!)

The boat came with a 1984 2-stroke Mercury 90 outboard motor, and we're trying to get it running. We hooked up the battery and a gas tank and tried to crank it over. The flywheel goes around partially (see video below) and it really acts like it wants to turn over. We've replaced all of the spark plugs, and cleaned the carburetors, which didn't seem to help. We do have battery power to the trim, though.

I took a video of it last night and put it on youtube in hopes that maybe somebody here could help diagnose the problem. I feel like it's a small problem that we're not seeing due to us not being mechanics. Please excuse our lack of motor knowledge- this is our first boat and we're learning along the way. Any help or insight would be greatly appreciated!

- Katy

 

[mfkadz]

I would try the following.

Remove the plugs and see how it turns over.

Seeing as it sat so long it could be really dry. Maybe some mystery oil in the through the spark plug holes will free things up. Tip the motor up so the holes are pointing to the sky. Put a little in a small container and pour some from the bottle to the container. Just enough for the treatment of one cylinder. There is no portion control from the bottle. Let it sit for a bit and then crank it a bit. That should help get the oil moved into the rings and the cylinder. Then let it sit overnight before trying to crank again. Hopefully by then it will have penetrated.

If it starts cranking for real it would be good to check the compression on each cylinder.

mike

 

[racerone]

Remove starter motor and take it apart for inspection,--All easy to do.

 

[emckelvy]

I noticed in the first part of the video that the battery cable was smoking! That indicates a poor connection and that'll eat up all the power instead of putting it to the starter.

2nd thing was the odd humming, this is not normal. If the starter is making that noise, you should take it apart & inspect, or if you have a local place that rebuilds starters & alternators, usually they will work on starter motors also.

Another thought, if the solenoid is making that funny noise, the solenoid contacts might be shot. After many uses the solenoid contacts get burnt, then this presents a high-resistance connection which keep full current from flowing to the battery.

Are you sure the battery you're using is good, and is fully charged? Many times you'd think it's the motor and really the battery is to blame. After charging the battery all night, you could take it to an auto parts store and they can run a "stress test" on it to see if it's still putting out enough amps to run a starter motor properly.

Note that any loose connections on the engine end can cause similar problems, make sure the battery ground cable is properly attached to a solid engine ground, and the positive cable is tight on the solenoid.

And Last but not Least, did you know that you could start your Inline Six with a rope??! :0

Yes, Indeed you can, and that might be a good way to see if it'll run, until you get the starter issue worked out.

Many times there is still an emergency rope in a pouch on the back side of the front cover (or in a plastic pouch in another place on the powerhead).

This rope will do a dandy job; carefully wrap around the flywheel, give some fast idle on the remote controls, primer bulb pumped hard, key to "ON", push-in and hold for primer/choke until it starts.

With water to the L/U, give the rope a stout pull and I wouldn't be surprised if it didn't fire right up!

HTH & let us know what you find.............ed

 

[scrapper042000]

these 90hps do pull a lot of current to start ,last one I had solenoid that was bad cranked very slow .....defiantely pull plugs to remove the load before trying to start ,and low voltage /poor connections always heat up fast ...that motor with the key off and the spark plugs removed should turn freely by hand at the flywheel ....good advice commander ...I like it ....wow just watched the video ,that humming =low voltage ......did you check battery voltage before you spend money on parts not needed ....if that keeps up your solenoid is going to weld the contact disk internally and then it wont stop cranking ...yes that's happened to me a few times .....yep pull plugs first ,turn flywheel by hand ,in my opinion

 

[mfkadz]

Ahhhh, I missed that in the first part. I watched the second part 20 times and could not find any smoke.

mike

 

[ktEOS]

Hello again!

Wow! Thanks for all of the responses! I will have my husband and our neighbors who have been helping read these (we live on a lake, so our neighbors have been helping us as much as they can).

We have taken the spark plugs out, and when we try to start the fly wheel definitely cranks faster than in the video. It definitely sounds better without the plugs, than with them.

Yes, the battery was smoking! It is a battery we borrowed from our neighbor and have been charging overnight. Looks like we'll be taking it to the auto store to get tested for enough voltage. I also did mention to my husband about a poor connection to the battery being an option. I watched a youtube video of a gentleman who had tried a bunch of different things to start his motor, but in the end his positive and negative wires to the battery had internal corrosion from salt water (he lived on the coast).

Anyways! We'll try some things out and see what happens and give you an update!

Thank you, so much, again!

- Katy

 

[Silvertip]

Clean both the battery end and the engine end of the battery cables.

 

[mfkadz]

Glad to hear the motor spins ok without the plugs.

So now it's just the starter hopefully.

And if you have visible corrosion on either end. The green stuff. Soaking in Coke will clean that up nicely.

mike

 

[ktEOS]

Well guys, we've made some progress! Still not fully turning over, but every day we get a little bit closer.

So far, we've cleaned the battery connections (had corrosion), bought ourselves a new battery (we were borrowing our neighbor's), and tried to start it with a rope. Cleaning the corrosion definitely helped.

Today, we cleaned where the ignition switch is wired and cleaned the connections again. A friend of ours is a diesel mechanic and we figured he could look and give us some sort of direction. After today, it is SO close to fully turning over. Our next steps are to change the battery wires (wires still get hot on the battery), try pumping fresh gas, and then after that, check carburetors. We've also found that one of the cylinders is not firing (out of 6).

So, we're making progress! We really appreciate the help and hope to report back soon with good news.

- Katy

 

[DavidMoore]

I recommend that you don't overlook the starter motor, 2 people mentioned it already.

My story

I've had my mercury 90 3 years now, was always a problem to start. This year after winter storage I had similar problems to yours, eventually, after doing everything listed above, I stripped the starter motor. It was full of corrosion and carbon dust, I blew out the carbon dust with a bicycle tyre pump, cleaned the rotor with and the copper contacts with a bit of wet and dry and removed all the bits of corroded metal from the stator magnets. Wow what a difference, my engine cranks like never before and now starts at the first / second attempt every time.

It's really not difficult to do, reassembly will be easier with a special tool to keep the brushes in place. You can easily make the tool yourself from an old ice-cream tub or stiff cardboard.

There is a you tube video that shows the tool, you can see it at about 20 min's in, recommend watching the rest of the video with the sound off.
Here is the link


https://www.youtube.com/watch?v=N48feMxZiI0

Don't forget to line up the alignment marks during the rebuild, this will ensure the stator does not go back upside down, if it does the starter will run backwards (don't ask how I know this :facepalm

Good luck with your project, with the cleaned carbs and new plugs I would put money on the above working out for you.

David