90 HP Won't Turn Over / Plugs?

[l008com]

So last year was the first year that our boat never made it into the water. It was winterized and we never got it re-winterized since we never even started it up. So cut to this year and I tried for a long time today and it just wouldn't turn over. This motor has been kind of famous for taking a long time to turn over, but once it does, it runs like a champ. This is the first time ever that it hasn't turned over.

So the gas tank was about 1/4 full with old gas. I really had no way to get rid of that so I just filled it with medium grade gas hoping that would be enough to get it to run.

Spark plugs are cheap enough that I figure if I'm going to bother taking them out to clean them, I might as well just replace them. I found a site online that said what kind the motor takes but I'd definitely like a second opinion. Oh and do you still have to gap spark plugs? I was reading a post on this website from 5 years ago about that. That wouldn't have even occurred to me.

So my questions are:
What kind of plugs does my motor take?
Do i need to gap them and if so, to what?
Does my problem sound like it might just be bad plugs? Or does it sound more like something else?

The motor is a 90 HP mercury, not sure of the year but I'd guess early 90s. We got it around 95-96 but it was used. So I'd guess maybe 92-94? I can take a picture and post it if that would help.

Oh and in a related problem... I can't open the case around the motor because it hits the hull of the boat. This is because the boat is in my driveway and even with the motor as far down as it will go (resting on a 2x4) its still leaned back pretty far. The only solution I was able to come up with would be to latch up the trailer to a truck (so it won't roll away) and jack up the rear of the trailer, probably a good foot or two up so I can lower the motor all the way, so I can open the case and replace those plugs. Is there an easier way to do this that I'm missing?

Thanks!

 

[verado7]

Re: 90 HP Won't Turn Over / Plugs?

running the old gas was a bad idea .

have you checked for spark? pull a plug put the boot on and have someone hold the plug against the block while you crank just hold the rubber boot with your hand and have them look for or hear the snap - if all is good there on all plugs start looking at a fuel problem - it would be a good idea anyway to rebuild the carbs and fuel pump -some carbs have the fuel pump built in and some dont just take your serial number to the parts person - kist are about 100 bucks and really simple to do just make sure you get the needle valve in the kit the old ones are likely stuck in the seats and not letting fuel thru - very common on a motor of that age and more prone when a motor sits long .

post back with your findings and we can help more

 

[l008com]

Re: 90 HP Won't Turn Over / Plugs?

Can anyone tell me what kind of plugs I need?

 

[l008com]

Re: 90 HP Won't Turn Over / Plugs?

Ok well I figured out what kind of plugs I need.

Now heres the deal, the other day it was cranking and cranking and cranking, but it woudln't turn over. Today, it wouldn't crank AT ALL! It's very strange. The other day it was cranking for I'd say at least an hour. Not non stop, I let it cool off between tries, but I was going for an hour. I actually had jumper cables connecting my idling car to the boat battery so it was cranking full speed.

Fast forward to today, it wouldn't crank a bit. I replaced the plugs anyway since i had them, and the old plugs were FILTHY. Horrible. I feel like if it would crank, it would start right up now. But it won't. I even tried turning the starter with a screw driver to see if it was on a dead spot (which would be very unlikely anyway, since i most certainly would have hit that dead spot the other day with all the cranking I did). But I checked the lights and horn, the boat is getting power. And I even took the step of sanding all the dirt off all the battery connectors, the O rings, so everything had a super clean connection. Still not a peep out of the starter. Any ideas?

 

[cell]

Re: 90 HP Won't Turn Over / Plugs?

Did you check the battery voltage?lights will still work with a low voltage.Sounds like if you had to keep er car jumped up to the battery it was a weak one to begin with.Are you sure you were in neutral?(I know dumb question but I did it beforeDid you tilt your engine back a little farther after changing the plugs?If so drop it down.theres probably a safety switch keeping you from starting your engine at that angle.
If you get it cranking squirt some fuel/oil mix in the carb...not starting fluid,and see if will turn over.If it does then Id look into a fuel problem.

 

[l008com]

Re: 90 HP Won't Turn Over / Plugs?

Did you check the battery voltage?lights will still work with a low voltage.Sounds like if you had to keep er car jumped up to the battery it was a weak one to begin with.Are you sure you were in neutral?(I know dumb question but I did it beforeDid you tilt your engine back a little farther after changing the plugs?If so drop it down.theres probably a safety switch keeping you from starting your engine at that angle.
If you get it cranking squirt some fuel/oil mix in the carb...not starting fluid,and see if will turn over.If it does then Id look into a fuel problem.

I actually had it hooked up to my car again today the whole time I was trying. So it's definitely not a weak battery issue. Since I killed it the other day before I Hooked it up to my car, I figured might as well hook it up from the start today. And I did have my motor all the way down. It was in neutral, and I even put it in and out of gear a few times. I tried pretty much everything. Giving it some gas in neutral for example. Choke, no choke. Things that really shouldn't effect NOT cranking at all. But I was desperate for a solution.

 

[verado7]

Re: 90 HP Won't Turn Over / Plugs?

when you crank it with the jumper cables does it turn fast ( normal) or really slow ?

if really slow pull all the plugs out and see if it cranks normal now - yes ? maybe partially seized.



if above doesn't apply change the starter solenoid (cheap enough to try) , pull the harnes apart at the motor and look for corrosion on the pins and in holes, neutral safety start on , ignition switch - you really need a manual and a dvom to trouble shoot this - the manual will have the voltage specs .


but the fact that it doesn't crank at all sometimes - i'm leaning toward solenoid, nuetral safety ,tilt safety (if equipped) and ignition switch in that order.

 

[l008com]

Re: 90 HP Won't Turn Over / Plugs?

After seeing the old plugs, I'm fairly confident that my problem the other day, where it cranked as much as I wanted, was a bad plug problem.

The problem today is totally different. Unfortunately, I don't even know what a solenoid is. But if you can show me where to get the part, and some instructions on how to remove it, I'm sure I can replace it

Does it make sense for something like that to work great and then just STOP working, suddenly, while the motor is idle?

 

[l008com]

Re: 90 HP Won't Turn Over / Plugs?

So lets say my starter is defective, how difficult is it to uninstall a starter, and reinstall a new one? Also I know autozone can check bad car starters, can they check boat starters too? If thats the problem, and I can replace it myself on the cheap, I'll go for that.

 

[Chris1956]

Re: 90 HP Won't Turn Over / Plugs?

If you trace the red +12VDC battery cable from the battery, it will end at the starter solenoid. On the solenoid is a thick cable that runs to the starter. the solenoid is a heavy duty switch that connects the two heavy cables together, to supply +12VDC to the starter. Take a jumper cable and connect one end to the battery + post, and touch the other end to the starter +connection, and see if the motor spins. the starter + connection, is the wire that runs to the solenoid. if the starter doesn't spin, it is bad. If the starter does spin, something else is bad (fuse, ign switch, wiring or starter solenoid).

 

[l008com]

Re: 90 HP Won't Turn Over / Plugs?

OK well. Today I pulled the starter. I touched direct battery power to it, very briefly, and boy did it spin. I reinstalled and turned the key, and nada. So it's clearly not a bad starter.



So there's the motor. How much is a starter solenoid? And WHERE in this picture is it? As a last resort, of they aren't too expensive, I figure i'll replace it and see if that fixes the problem. And if not, i'll just bring the boat somewhere to get repaired. But i'm poor so I'd like to do it myself

 

[sschefer]

Re: 90 HP Won't Turn Over / Plugs?

The starter solenoid is the bottom solenoid between the switch box and the starter. It is the one where the battery positive lead connects to the terminal on the right and the starter lead connects on the left.
There are two more immediately above it for your trim/tilt. Notice the green wire and the blue wire connected to them, green is down and blue is up. Don't worry about them I'm just telling you for refernce to the starter solenoid.

Before you change it, check just below where the starter + lead connects to the starter. There is a red wire with a 20amp fuse inline. If that fuse is blown your engine won't crank. You can check it with a simple automotive circuit tester.

Nothing else has any obvious signs of failure but the starter looks original and an hour of cranking on an old starter may have caused enough load over time to breakdown and finally blow the fuse.

 

[l008com]

Re: 90 HP Won't Turn Over / Plugs?



So is this correct? I'll try to check that fuse later on today. Wouldn't that be great if it was that simple I could be boating in no time!

 

[sschefer]

Re: 90 HP Won't Turn Over / Plugs?

So is this correct? I'll try to check that fuse later on today. Wouldn't that be great if it was that simple I could be boating in no time!

Yep, that's the ticket. The red fused wire goes to the red at the ignition switch and comes back to the solenoid as the yellow/red stripe wire. The yellow/red wire also passes through the neutral lockout switch at the control so you might also check that. The yellow/red wire will only have power on it when the ignition switch is turned to the start position and the control is in neutral or in the warmup (gear shift disengaged) position. It will not have power in the run position.

 

[l008com]

Re: 90 HP Won't Turn Over / Plugs?

What I originally circled was not what I was thinking. I was circling that huge black tube think, but the fuse is actually the smaller black tube with red wires coming out of each end. Either way, the fuse was corroded but not blown, and replacing it anyway didn't help. Still nothing. Although it does click when you turn the key. Just one weak click coming from the motor. Not like the starter is trying to turn, nothing that powerful. Just a little tick like.. somethings doing something?

So any other thoughts at this point?

 

[l008com]

Re: 90 HP Won't Turn Over / Plugs?

UPDATE: OK so I believe I found my motor's serial number, and the proper solenoid it takes. So maybe tomorrow I'll head over to west marine, again, and give this a shot. If this doesn't work, what else could it possibly be? Where can I find the neutral switch, and how would I test it?

 

[OkcOffRoader]

Re: 90 HP Won't Turn Over / Plugs?

starter solenoid...like he said, follow the positive cable from the battery, the other end of it is connected to the solenoid...carefully note the location of the wires before removal to ensure you dont cross them on install...

 

[sschefer]

Re: 90 HP Won't Turn Over / Plugs?

UPDATE: OK so I believe I found my motor's serial number, and the proper solenoid it takes. So maybe tomorrow I'll head over to west marine, again, and give this a shot. If this doesn't work, what else could it possibly be? Where can I find the neutral switch, and how would I test it?

If you're getting a click that's the solenoid. Have you ever bypassed a solenoid to start a car? I don't recommend doing it if you haven't done it before but you use two large screwdrivers to jump across the large battery terminals of the solenoid. Hold on to the handles and put one tip on each LARGE battery terminal and touch the two shafts together momentarialy. It's going to spark and leave a weld mark on the shafts but that is normal. The starter should engaged and run. If not, your problem is not the solenoid, its either battery, cable or starter. If you're at all skeptical about how to go about this procedure, don't do it.

 

[l008com]

Re: 90 HP Won't Turn Over / Plugs?

Yeah I'm not going to do that. I'll just replace the solenoid, and if that doesn't work. I'lllll beeee baaaaaaack . . .

 

[Silvertip]

Re: 90 HP Won't Turn Over / Plugs?

Let's get some terminology straight.

Won't turn over means the starter is not cranking the engine.
Cranking means the starter is spinning the engine.
Cranking and turning over are therefore the very same thing.
"Won't start means the starter is cranking the engine but it "won't start".

The item you have circled looks to me like its the main engine to control box harness connector. Cranking issues are very often bad battery cable connections on the battery or at the engine. Disconnect both ends of both cables, make them shiny clean and reattach them tightening them securely.