RPMs dropping

[Jharrisok]

Okay guys, I’m needing some help. Does anyone have any clue why my RPM’s randomly drop for a split second? It only starts after about 20 minuets of running and then continues the rest of the day. It seems to be worse when running between 5-6k RPM and when pulling a wakeboarder or tuber. I’ve replaced the plugs and checked the plug wires. This is the only video I got of it doing it but usually it’s worse. I have a video but I can’t seem to post it on here.

 

[Midnight2V]

A spark plug set can tell you an entire story about what is happening in the engine.

Was there anything obviously wrong with the plugs or did they look alright? Were any of them a different color (reddish-yellow or blue) on the porcelain, the electrode, or the ground strap? Were they greasy, oil covered, dry? Did any of them smell like gasoline?

 

[FLBulldogger]

I've never experienced it and I don't know that it affects us NA's but I remember back before I bought the boat in my research here on this board and the other board an issue with heat soak that seemed to afflict the SC boats your symptoms kind of describe heat soak, IMHO, @haknslash, @SamCF and others have refit there engines if memory serves me and I'm sure plenty of others also, I found this thread here for you may help you understand if this is the issue or not https://jetboaters.net/threads/sx-192-mods.6550/ good luck and I'm sure you will get some good advice from the folks here.

 

[Midnight2V]

I had the heat soak on my boat, but it never dropped me below 6300 RPM and it was never a sudden drop but a gradual reduction in peak RPM. I don't know to what extent it would affect NA boats other than causing the engine to reach a temperature limit either due to fouling or a clog in a cooling line.

JHarrisOK, is your boat supercharged? I can't tell from your profile. BTW, I see you are in OKC. I just move from OKC to Houston this winter. What lakes do you frequent?

 

[Jgorm]

It sounds like a miss. My fx140 does almost the exact same thing. Runs fine early in the day, but then drops nearly 1000 rpm and 8mph sometimes. Sometimes it comes back to full speed, but sometimes not. It feels like someone just turns off and on one cylinder. I'm pretty sure it has bad compression on 3 causing that cylinder to miss. Maybe it's a valve clearance issue where it needs a smaller shim and the exhaust valves are not fully closing once they warm up.

 

[Jharrisok]

I had the heat soak on my boat, but it never dropped me below 6300 RPM and it was never a sudden drop but a gradual reduction in peak RPM. I don't know to what extent it would affect NA boats other than causing the engine to reach a temperature limit either due to fouling or a clog in a cooling line.

JHarrisOK, is your boat supercharged? I can't tell from your profile. BTW, I see you are in OKC. I just move from OKC to Houston this winter. What lakes do you frequent?

The boat is a 2014 AR192. It is super charged and I upgraded the intercooler to the SHVO a couple years ago. I also did the ribbon delete, now I wonder if one of those could be the source of the problem? Heat soak is not the problem, I had that before I changed the intercooler now it’s almost completly gone. I’m thinking something electrical or maybe valve?

We go to Arcadia a lot since I live in Edmond and we just bought a place at Eufaula so we will be going there more now.

Thanks for offering up suggestions!

 

[haknslash]

Can you upload the video to YouTube or someplace? The forum won't allow you to manually upload a video as it's not set up for hosting them unlike a picture.

Heat soak wouldn't cause a temporary drop like a spike and since you've already resolved that with the intercooler upgrade and ribbon delete that rules it out. My RPMs would drop to 7200 when I would have heat soak on the stock intercooler but it was always consistent and never a spike or miss type feeling in RPM.

Since you mentioned it happened more when pulling someone I have to think it's related to a load. Would a bad TPS sensor cause this issue? They have a history of going bad and being finicky. It would be interesting to see what a data logger or YDS would show. Any codes being thrown? Bad gas maybe?

BTW you can change your boat profile so that it shows 192 instead of 19 so it will help others out know your boat. Get the video uploaded and hopefully others can chime in to help isolate the issue.

 

[Jharrisok]

Can you upload the video to YouTube or someplace? The forum won't allow you to manually upload a video as it's not set up for hosting them unlike a picture.

Heat soak would cause a temporary drop like a spike and since you've already resolved that with the intercooler upgrade and ribbon delete that rules it out. My RPMs would drop to 7200 when I would have heat soak on the stock intercooler but it was always consistent and never a spike or miss type feeling in RPM.

Since you mentioned it happened more when pulling someone I have to think it's related to a load. Would a bad TPS sensor cause this issue? They have a history of going bad and being finicky. It would be interesting to see what a data logger or YDS would show. Any codes being thrown? Bad gas maybe?

BTW you can change your boat profile so that it shows 192 instead of 19 so it will help others out know your boat. Get the video uploaded and hopefully others can chime in to help isolate the issue.

Thanks, I've updated my profile.

I have the video posted on the Yamaha Jet Boat Owners USA (Official Group) FaceBook. Link below, if you are a part of that FB page.
https://www.facebook.com/groups/164...tif_id=1527600022675275&notif_t=group_comment

 

[haknslash]

I watched the video and thanks for posting it. I don't think that is fuel related. Definitely seems electrical like something is wrong with spark or ignition. I would check all over the engine and look at the harnesses to make sure all connectors are plugged in and nothing looks like it's coming apart (wires being pulled from connectors included). By how intermittent the RPM's drop it almost seems it's like something is loose but that that doesn't really explain why your RPM is down in general from the 7600-7800 RPM it should be at with those mods at or near sea level).

Does it idle ok? Does the boat feel slower or sluggish all throughout the powerband or does it feel like it normally did in the past with only your RPM's are acting up at WOT?

 

[Jharrisok]

I watched the video and thanks for posting it. I don't think that is fuel related. Definitely seems electrical like something is wrong with spark or ignition. I would check all over the engine and look at the harnesses to make sure all connectors are plugged in and nothing looks like it's coming apart (wires being pulled from connectors included). By how intermittent the RPM's drop it almost seems it's like something is loose but that that doesn't really explain why your RPM is down in general from the 7600-7800 RPM it should be at with those mods at or near sea level).

Does it idle ok? Does the boat feel slower or sluggish all throughout the powerband or does it feel like it normally did in the past with only your RPM's are acting up at WOT?

It idles fine and that wasn’t WOT but the best RPM I’ve ever got was 7400. When it’s not “missing” it seems normal. I pushed every connector I could see to make sure it was connecting but now I think I will take them all apart and visually check them to see if I see something. Thanks for the input!!

 

[haknslash]

What is your altitude where you boat? What was your best top speed at 7400 RPM? I have the same mods and at my elevation (600 ft) I'm 49 MPH (gauge indicated) at 7600 RPM throughout the day. With it happening in a range of RPM I wonder if it's just enough vibration for a loose wire or something to start acting up? Please keep us posted what you find!

 

[SamCF]

Check the map sensor and Cam Position Sensor. If there is anything wrong with either of those it will cause reduced RPM or complete shutdown. No alarm codes??

 

[SamCF]

Also, it hits your supercharger clutch hard every time your engine cuts out under boost. Don't keep driving it like that.

 

[Jharrisok]

Check the map sensor and Cam Position Sensor. If there is anything wrong with either of those it will cause reduced RPM or complete shutdown. No alarm codes??

No codes. I’ll check the sensors, thanks.

 

[Jharrisok]

Check the map sensor and Cam Position Sensor. If there is anything wrong with either of those it will cause reduced RPM or complete shutdown. No alarm codes??

How do I check the sensors?

 

[Jharrisok]

I wanted to update you all, I figured out the problem!!!! It was just a wire connection that had come loose. I reconnected it and it runs perfect! Thank you for all the input. If anyone happens to know what this wire does I would be happy to know.

 

[Jgriffy]

We’ve survived hurricane Michael, only to now get our boat out to relieve some stress to only find that we’re having the same issue as above-RPMs barely above 5500! Ughh. Replaced the impeller, wear ring, plugs-no improvement. It feels like the boat is loaded down with water in the hull and cannot get up on plane or that it’s governed! I took off the intake hose, and could feel the fins on the supercharger, they spin both directions. Yikes, supercharger replacement is like $5k and my extended warranty ran out end of March-yuck. Any ideas? Gear assembly behind supercharger? FYI, air filter housing rubbed hole in oil filter, blew oil all in engine compartment...limped back to my dock, threw overheat code. Could it be this code still, tho it doesn’t show it? Preciate the assist fellows, from Panama City, FL

 

[SamCF]

You likely only need to replace the supercharger clutch. I haven't done one, but a handy person should be able to do it.

Video of repair:

How to install SHO / SVHO Supercharger clutch Video

Here you go guys this is a run threw start to finish on how to install sho / and svho supercharger clutches https://youtu.be/3xfb0cyD1x part 1 https://youtu.be/MB-YwUqD6_o part 2

greenhulk.net

Dean's Team clutch that will last forever:

CR Yamaha Heavy-Duty Supercharger Clutch Assembly [CR Clutch] : PWC Performance Parts

PWC Performance Parts CR Yamaha Heavy-Duty Supercharger Clutch Assembly [CR Clutch] - After years of development and testing, we're proud to introduce the most durable heavy-duty clutch on the market! Whether you are serious racer, running on lakes on the weekend, or jumping waves out in the...

www.4-tecperformance.com

Stock clutch that is a direct oem replacement:

Yamaha OEM Supercharger Clutch – 2013-2016 SHO

New Yamaha Genuine OEM replacement supercharger clutch. Used on 2013-2016 Yamaha 1.8L SHO engines. (updated 57 tooth clutch) New oil pump assembly gasket is required when replacing this clutch. (par

rivaracing.com

 

[Jgriffy]

You likely only need to replace the supercharger clutch. I haven't done one, but a handy person should be able to do it.

Video of repair:

How to install SHO / SVHO Supercharger clutch Video

Here you go guys this is a run threw start to finish on how to install sho / and svho supercharger clutches https://youtu.be/3xfb0cyD1x part 1 https://youtu.be/MB-YwUqD6_o part 2

greenhulk.net

Dean's Team clutch that will last forever:

CR Yamaha Heavy-Duty Supercharger Clutch Assembly [CR Clutch] : PWC Performance Parts

PWC Performance Parts CR Yamaha Heavy-Duty Supercharger Clutch Assembly [CR Clutch] - After years of development and testing, we're proud to introduce the most durable heavy-duty clutch on the market! Whether you are serious racer, running on lakes on the weekend, or jumping waves out in the...

www.4-tecperformance.com

Stock clutch that is a direct oem replacement:

Yamaha OEM Supercharger Clutch – 2013-2016 SHO

New Yamaha Genuine OEM replacement supercharger clutch. Used on 2013-2016 Yamaha 1.8L SHO engines. (updated 57 tooth clutch) New oil pump assembly gasket is required when replacing this clutch. (par

rivaracing.com

Man I hope so thank you so so much for the info will check it out!

 

[D3nN1s]

Just had this happen to me... hope it’s just the clutch