Mercury 90hp Jet Sport Issue (Please help new boater!)

[JW-JetBoat]

Hi everyone,

I'm new to boating and here. I just purchased a 1995 Thundercraft Typhoon Jet Boat which uses the 90HP Mercury Oil Injection 2 Stroke Engine, which I've read on the forum is actually a Force engine branded as Mercury?

Previous to this I had a 1995 Northstart Blast with the 90HP engine less the direct oil injection and had no engine issues.

The Typhoon has been sitting for a year or so, and had a small amount of old gas, but I filled it up with new gas, was able to get it running and it was idling fine for a while, no problems, so I took it out on the water. As soon as I got out of the bay and gave it a little gas it died out. Got it to start again playing with the choke and throttle as I started it, and again as I gave it some power it died out.

From the short time I had it out I noticed these things...
- Putting it back to idle would kill the engine after the second start up
- I'm not 100% sure but I think the engine died both times when I was turning the wheel
- There was some smoke coming from the engine after the second time, it has been sitting for a while so I think it was just burning out old build up
- The boat would not turn over the 3rd
- When I was in idle and slowly coming out of the bay, the boat ran very well and was quiet, when I did give it a little bit of throttle the vibrations were a little rougher than my previous boat the 1995 Northstar
- The engine I believe had a knock in it on the first fire up, but I'm pretty sure this was due to it burning the old gas
- After the second time, I couldn't get the engine to turn over. It would turn very slowly and barely complete a revolution. I noticed the boat does not have a marine battery, this could have something to do with it too, but doesn't explain why it was dying..


So it could just be burning out the last bit of the old gas and I didn't have a good enough battery for the starting and stopping, or it could be more. I just want to hear what people with these engines or similar have experienced.

I am not a big mechanic, but I thought it could be some build up in the carbs, I was also suggested to change the fuel water separator, but have no idea where that would be

I've also heard terms "Switch box" and "Stator" on the forum doing a search, and have no idea what they are!

Any help is appreciated!

Thanks!

 

[Faztbullet]

Re: Mercury 90hp Jet Sport Issue (Please help new boater!)

You need to check the basics.. spark, compression and fuel,remember no fuel = no lubrication. If it has been setting a while as you posted check compression 1st, spark on all cylinders 2nd and clean the carbs 3rd.

 

[JW-JetBoat]

Re: Mercury 90hp Jet Sport Issue (Please help new boater!)

Update: So I checked the spark plugs, and all are good. The battery was cooked I needed a new one. Drained some gas and took out the carb's and will get them rebuilt over the next few days.

I'm thinking it was dirty gas, and bad carb. If it's not that, then perhaps the switch box? From reading on the forums I understand this is essentially the ECU for the boat and it could be that.

One thing I noticed there is no fuel filter on this boat, I am going to cut the gas line and put in one myself.