1994 Mercury 90HP Sport Jet (force) Starter Issue

I just bought a 1994 Sea Ray Sea Rayder jet boat with a 1994 Mercury 90HP Sport Jet (force) motor. The previous owner let it sit for a year with gas in it so the first thing I did was pumped out the bad gas and rebuilt all three carbs. I noticed that the cranking was a bit weak even with a brand new and fully charged battery. I also noticed that the bendix on the starter would disengage often as I was cranking and the motor not running yet. So I took the starter out, took it apart, cleaned it up (everything looked good inside), and installed a new drive kit (spacer, spring, washer, and bolt) and a new bendix (the old one was slipping internally).

Once I got everything back together the motor will crank without the bendix disengaging most of the time but there are still times when the bendix will disengage and the starter will rev up. I turn the key to the off position, wait a few seconds, and try again. Sometimes the bendix will engage and then disengage almost immediately and other times it will crank without the bendix problem.

I can get the motor to start and run both with a hose attached and sitting in the water tied to the dock. Was about to take her out for a test but then the overheat alarm came on. I am investigating that now and will post questions later if I cannot solve that one.

Anyway, any ideas why the bendix will intermittently disengage from the fly wheel or is this a common thing and I am just ignorant of it since this is my first boat?

Appreciate the help.

Re: 1994 Mercury 90HP Sport Jet (force) Starter Issue

Hi, Charlie.

Welcome to iboats.

Kind of unusual symptoms for this, but it is easy and free to fix if it is the problem.

Hidden corrosion in the connections of the battery cables really limits the current available to the starter and it sounds like you don't have enough current there.

Try removing, scrubbing shiny and reconnecting all connections of the big battery cables.

Good luck, and let us know what happens.

Re: 1994 Mercury 90HP Sport Jet (force) Starter Issue

As JB said clean the contacts on the main cables. The earth wire where it connects to the block of the motor can corrode and is difficult to see as it is tuck away.
These starter motors are different to a car starter as they don?t have a solenoid to hold the bendix gear up onto the ring gear. It is only the inertia of the bendix gear not spinning as fast as the starter that lifts it up to the ring gear. Once the gear is engaged it?s only the resistance from the motor that holds it there. If the motor kicks the bendix gear will drop off of the ring gear and stay down until the starter stops spinning. If the bendix gear is spinning the same seed as the starter there is no force to push it up.
It?s quite common to have this happen especially when the motor is cold and kicks a bit but doesn?t start. As long as the starter turns the motor over at a decent speed you should be OK.

Re: 1994 Mercury 90HP Sport Jet (force) Starter Issue

Thanks for the responses gents. I will give that a shot. I did clean the contacts for all the wires on the starter solenoid and the red wire that goes from it to the starter when I had the starter out a few days ago. I'll check all the other contacts and the ground wire tomorrow.

So in recent news, I took the boat out to the ramp since it was running great in my driveway after replacing the fuel filter and a few of the fuel lines. Ran great attached to the dock so I idle'd her out passed the no wake signs and then slowly took her up to speed. It felts under powered based on what my expectations were but planed out pretty quick. Took some turns and all seemed good to go. Turned to take it back in and pick up my wife and daughter to take them for a ride and just as I got it pointed toward the dock the motor died. It wouldn't restart no matter what I tried and the battery died from the on and off cranking. 45 minutes of "Row Row Row My Boat" later I was back at the dock laughing about it.

Tomorrow I will pull the spark plugs and poke around to see if I can find anything suspicious that might indicate what happened. I was at WOT and everything seemed fine and then suddenly I am dead in the water.

Oh, and what is kind of funny, I pulled the rookie mistake of putting it in the water without the plugs before all this happened. Thankfully no one was around to witness it. Bilge pump on and ran for the truck to pull it out and put the plugs in. Haha. Oops. Not sure how high the water got but it did get over the bottom of the motor itself. I don't think it got high enough for water to enter the lower carb.

Re: 1994 Mercury 90HP Sport Jet (force) Starter Issue

Have you managed to get the motor to start again?

The first thing I would do if it cut out at WOT is a compression test.

If that checks out OK see if you are getting a spark. You can get a cheap inline spark tester at an auto store or make one of ?fucawi??s home made testers.

Then start looking at the fuel side.

It could be something as simple as a split fuel pump diaphragm. The shock of being used may have been too much for it.


I?ve done the bungs thing at the ramp too!

Good Luck

Re: 1994 Mercury 90HP Sport Jet (force) Starter Issue

Two Fish .....The starter on a car with a solenoid to hold the pinion in gear is called a Pre Engaged Starter ...... The ones on the outboards are called Inertia starters .. Bendix is just a makers name not a part ...More American Crap Steve in Noosa

Re: 1994 Mercury 90HP Sport Jet (force) Starter Issue

Haven't got it started yet since then. I only tried for a few seconds and then decided to get all the terminals off and clean them before trying again. Bad news is I snapped the bolt that all the ground wires were connected to the engine block with. It was froze up. I did find a bit of corrosion on those connections though. So now I have to solve the broken bolt issue and then will be able to proceed with the rest.

Re: 1994 Mercury 90HP Sport Jet (force) Starter Issue

That?s bad luck. Hopefully the corrosion there was the problem.

You could try a machine shop and get them to drill out the bolt and fit a new thread.
You could find another bolt or nut on the block of the motor to attach it to. Stay clear of any fuel sources just to be safe.

Re: 1994 Mercury 90HP Sport Jet (force) Starter Issue

just purchased a 96 thundercraft typhoon with a 90hp sport jet in it. had it out the other day and ran great for 45 min, then couldn't get it past trolling speed. filled fuel tank, added fuel conditioner, topped up oil with a synthetic 3 oil... starts fine... if i idle back to neutral, wait a few seconds then open it up she goes great for about 20 seconds then cuts back again. And talk about fuel consumption. Seems that these are common issues with this engine. Does anyone have any good news stories on these engines? should I sell this boat now?

Re: 1994 Mercury 90HP Sport Jet (force) Starter Issue

As Fucawi mentioned, the pre-engaged starter (car starters) will engage first and then turn over and will stay engaged until you let go of the switch from the starting position, even after the engine is running. The outboards has inertial type starter drive which will turn over first (to move the drive pinion forward by means of the worm thread on the shaft) before engaging the flywheel gear, engaged, continue turning until the engine fires or runs. When the engine fires even on one cylinder (intermittent or "coughs") only and not necessarily the engine running, the flywheel will turn faster (because of higher gear ratio) than the starter pinion drive, disengaging it in the process. If you continue to hold the switch in the start position, the starter will freewheel against the flywheel bottom without engaging. So you will let go of the switch turn it off and try starting again. What you have is not a starter problem but an engine starting problem. The starter disengaging when the engine "coughs" is totally normal. And this always happens when the engine is cold. You might want to check the idle screw setting first and then also the idle fuel/air mixture screw. There's a sticky post for setting these.

Re: 1994 Mercury 90HP Sport Jet (force) Starter Issue

If the broken ground bolt doesn't hold anything except ground wires, you can either try removing it or drilling and tapping a new bolt hole right next to it and make it a new grounding bolt. Obviously, if it holds or bolting something together other than ground wires, there's no other options except to drill it out.