2017 Scarab 165G Motor Issue

[globaldude]

I'm having a motor issue with my boat (2017 165G w/130hp, non-turbo). It runs fine until it doesn't. It looses power like it's either not getting enough fuel or spark. $$$$ later, the local dealer can't figure it out. The dealer read a MAP sensor code when they hooked upon their computer but the sensor tested fine. They recommended I replace the battery so I did. Took boat out again and it did it again....runs fine then spit, sputter, stall then starts up again like it never happened. So, I limped back to the dock.

I'm at a loss. If I got some bad fuel somewhere, wouldn't it run bad all the time, not just sometimes?. I saw a video once where a guy replaced the filter inside the fuel tank but I can't find it now.

Any help here would be much appreciated. Especially since the dealer's only success so far is taking my money.

 

[Luc Lafreniere]

First, just to ensure you have the correct information, your engine is a 150HP, not 130. Also, it's called a supercharger, not a turbo. Turbos are a different type of device. They both give extra power but using different methods entirely. Rotax engines use superchargers on the bigger HP engines. Not trying to be an a-hole... just want you to know so you have the right info in the future. But definitely no supercharger on the 150HP.

As for your problem... yeah, sounds like that dealer knows nothing. I'd start by simply replacing your spark plugs. Easy and cheap to do. If it doesn't work, then you'll have spares. Make sure to inspect the old ones.

The filter is very unlikely to be the cause. It's like a thin sponge inside the tank. It just prevents particles from getting in the pump. It's not supposed to be changed but it can be if you really want to. It's a pain if you're not mechanically inclined. You need to pull out the entire fuel sender out of the tank located under the middle seat of your boat. I'd recommend avoiding this for now. I highly doubt this is it.

Another possibility could be a bad electrical connection. Tracking it down though is not easy..... that's where you need some actual pro usually unless you're very knowledgeable in the electrical system.

I highly suspect your dealer is not a Scarab dealer? If that's the case, I'd recommend finding a local Sea-Doo guy to help. Sea-Doo mechanics will know exactly how everything works. The only issue they may have is not being able to connect to the computer since they need a specific Scarab computer license. Usually they only have the Sea-Doo one unless they've worked on Scarabs before.

 

[globaldude]

Roger that...not sure why I said 130hp when I knew it was 150hp. Saying non-turbo was ignorance on my part ---it's non-supercharged. Thanks for the lesson.

I inspected & re-gapped the plugs but did not change them since they looked fine. I could change them since it's easy enough. I can do most things myself when it comes to replacing items. I just don't know where/what to replace. The dealer I took it to sells Scarabs & Sea-Doos. They just couldn't figure it out. I plan on taking it out again today to see what happens. Hopefully I don't get stranded. I'll look around for a Sea-Doo mechanic willing to look at it. Appears I'm chasing a ghost on my Ghost.

 

[Luc Lafreniere]

Yeah, if you've checked the plugs, it's less likely, but very inexpensive to replace them. Also, inspect the ignition coils, make sure there's no damage/corrosion and that they are properly seated on the spark plugs. Presumably the small silver terminals on the spark plugs have been correctly removed... I assume it is since you did take them off yourself on top of the dealer presumably looking. But I say this because we've seen it all on this forum. lol

From your symptoms, it really sounds like an electrical problem. Ground wire maybe... but this is the hard part. Intermittent electrical connections can be hard to diagnose. Inspect all wires/connections. Take apart the red master switch and ensure all connections in there are solid and clean.

Ghosts/gremlins/other.... always frustrating.

 

[Cobra Jet Steering LLC]

Sounds like some corrosion on the electrical connections to your mpem computer clean all the connections to the plugs on the wire harness.

 

[globaldude]

Do you know where then mpem computer is located on my boat?

 

[Luc Lafreniere]

to my knowledge, the mpem is a fuse box on our boats. It's the fuse box located behind your battery. All the electrical connections related to the engine are there. As I was saying, you need to inspect all electrical connections (which includes this fuse box) + the red master switch also located near the battery. All of these connections can get corroded over time, especially in salt water environments.

 

[Cobra Jet Steering LLC]

Do you know where then mpem computer is located on my boat?

https://www.scarabjetboats.com/uploads/2016/11/ScarabPIG2017.pdf see if it is in here or look on line for a service manual.

 

[globaldude]

I did replace what I'll call the starter relay and ignition switch because I'm also experiencing an issue when the boat sets for a while (sometimes just overnight), I have to turn the key on & off several times before the starter engages to turn the motor over.

 

[Luc Lafreniere]

If the new relay (in fact, there are two relays in that fuse box behind your battery) and ignition switch were replaced correctly and have proper connections, it won't explain the issue. But if either isn't seated properly, or a terminal is loose, wire damaged during the install proces....

Were your issues present before the relay/ignition were replaced?

 

[Cobra Jet Steering LLC]

The mpem is a computer that runs your engine etc I had one with the same engine in a p w c that would do what you are experiencing and worse it would shut off the engine without warning, and that could get someone seriously hurt especially with the tricks I do I would pull the wiring plugs from it and spray them with silicon spray and then it would run ok for a while and then surprise me again. if you have been getting water in your hull that can be the cause if that is the issue I also had issues with the same P W C loosing top speed and that ended up being an exhaust leak in the hull reducing the oxygen levels required for high speed. Imagine doing this and the engine just shuts off without warning,

 

[Luc Lafreniere]

@Cobra Jet Steering LLC I don't think newer Rotax engines have an MPEM anymore. It's just a fuse box. There's an ECU though... is that what you're trying to say? Engine Control Unit. Those are not the same.

 

[Luc Lafreniere]

I can see why there may be confusion.... I've only been on Rotax engines since relatively recently. But I can see from this page that the MPEM and ECU used to be the same. What is MPEM and ECU on a Sea-Doo? [Explained] - JetDrift

 

[Cobra Jet Steering LLC]

The brain that ran the engine was a box with a large plug that would cause a lot of issues however It has been many years since I owned any sea doo or 4 tec products I did check the internet to be sure they still used those and the mpem still showed up for his model year

 

[Cobra Jet Steering LLC]

I would be cleaning all the ground wires also . Today I spray every connector with white lithium grease before the engine ever hits the water and I have not had any electrical issues since doing that but I also spray the entire engine with that as well and I never hose off the engines unless salt water gets in the hull.
One more thing, I believe those engines also have a neutral safety switch as well as a throttle positioning sensor and if either one is not working correctly it will not start. I had that problem once with a Yamaha.

 

[Luc Lafreniere]

MPEM does not show up anywhere on the parts diagram. I've also never heard of this in any of the Scarab world. ECUs on the other hand... those ARE in the parts diagram and I've heard plenty about them. Based on your description, I think you mean the ECU on these. Part 60 in the diagram.

But the fuse box behind the battery is a prime culprit for bad connections. Lots of stuff going on there. But the ECU connections can also be checked as @Cobra Jet Steering LLCis mentioning.

Did I mention, check all electrical connections? lol Did I mention you may need a pro involved? lol Lots of potential fail points across all of these areas.

 

[globaldude]

Just returned from my test run with no change. Boat starts fine then looses power. Had a strong fuel smell. The motor continues to run if I feather the throttle but not much power. When I returned, I cleaned the two 30amp relays in the fuse box (both had slight corrosion) & put some dielectric grease on the pins. I couldn't quite pinpoint the ECU.

Here's two photos - one shows the fuse box and the starter relay I replaced before. The other photo shows what might be my ECU (box on lower large hose). Still chasing ghosts...

 

[Luc Lafreniere]

Fuel smell???? That is definitely not normal. I'd investigate that asap. Nevermind electrical connections right now. You need to check your fuel line and all associated connections. Under your middle seat as mentioned before is an access panel, 6 screws and you can see teh top of the fuel sender. I'd check that first. Then follow that line.

No error codes on screen at all?

 

[Cobra Jet Steering LLC]

Is it possible to run with the engine compartment open to allow more air flow and also run with the filter removed from the end of the hose?
Sounds like it is chocking out. also check the fuel tank for water, get a small hose and put it all the way down to the bottom of the tank and siphon out some fuel , put it in a clear gallon bottle and let it sit to see if there is water in the tank , I had a situation where I had the same issue and I placed a water separator on the fuel line , to remove the water.

 

[globaldude]

I probably didn't describe the smell correctly. It smelt like unburnt fuel not raw fuel. I believe the smell came from how rough the engine ran. The engine didn't respond (good or bad) how rough the engine was running when adding more throttle; only how much unburnt fuel I smelt. There was no check engine light either. I might need an exorcist.