| MudmotorTalk.com http://mudmotortalk.com/mmt_v2/ |
|
| RPM drops drastically above 4200 http://mudmotortalk.com/mmt_v2/viewtopic.php?f=3&t=74730 |
Page 1 of 2 |
| Author: | SlimOx [ Sat Nov 16, 2019 12:31 pm ] |
| Post subject: | RPM drops drastically above 4200 |
Guys, Having trouble getting my tech on the line. See below: First off, I've had cam, rods heads etc done by a well known tech. Boat ran fine all day until randomly in open water I had the below issue: Anything above 4200 RPM the rpm reduces greatly and I have to back off throttle to keep the boat from slowing down. As long as I stay below 4200, she runs perfect. Anything above it loses propulsion and RPMS drop. This occurs in or out of the water. Thoughts? Valve lash is good. Prop/internal issue? Never had anything like this happen before. Thanks for the help. |
|
| Author: | Will [ Sat Nov 16, 2019 12:48 pm ] |
| Post subject: | Re: RPM drops drastically above 4200 |
Carb or EFI? Are you hitting the rev limit? |
|
| Author: | SlimOx [ Sat Nov 16, 2019 12:58 pm ] |
| Post subject: | Re: RPM drops drastically above 4200 |
Carb. And everything seems normal there... Fuel may be the culprit? I did come very close to running out of fuel. Maybe filter? Or does anyone know about the high pressure fuel pump? Do those go out? Boat has 165 hours on it (so fuel pump). New build around 130 hours. |
|
| Author: | SlimOx [ Sat Nov 16, 2019 12:59 pm ] |
| Post subject: | Re: RPM drops drastically above 4200 |
Will, I think I hit the limiter but it drops out so quickly it is hard to tell. If I stay on WOT it won't get there....stays well below 3200. If I adjust throttle to stay at 3200 it runs perfect. That is why I might diagnose as fuel system. |
|
| Author: | Russ [ Sat Nov 16, 2019 1:51 pm ] |
| Post subject: | Re: RPM drops drastically above 4200 |
There isnt a high pressure fuel pump on a carbed motor. Theres one fuel pump. It sounds like its not keeping up.when it starts doing that, pump the bulb and see if it helps. #CFFITR #GhostBoat #Whoneedsphysicsihaveamudmotor |
|
| Author: | SlimOx [ Sat Nov 16, 2019 2:29 pm ] |
| Post subject: | Re: RPM drops drastically above 4200 |
I'll try that. Also, when I checked valve lash there was some oil/dark fluid inside. Does this indicate anything? I don't recall that being normal. |
|
| Author: | Russ [ Sat Nov 16, 2019 2:47 pm ] |
| Post subject: | Re: RPM drops drastically above 4200 |
Oil has to be up there or the rockers have no lubrication. Completely normal. #CFFITR #GhostBoat #Whoneedsphysicsihaveamudmotor |
|
| Author: | SlimOx [ Sat Nov 16, 2019 2:54 pm ] |
| Post subject: | Re: RPM drops drastically above 4200 |
Ok - seems like quite a bit. Continued priming on the bulb did nothing. Not sure where to go now...checked all wires for grounding etc. Everything looks normal. Thoughts on prop issues? Never taken a lower assembly apart on one of these? Is it similar to an inboard/outboard where the prop can be slipping at high rpm? It does it regardless in or out of water so that seems unlikely. |
|
| Author: | SlimOx [ Sat Nov 16, 2019 3:11 pm ] |
| Post subject: | Re: RPM drops drastically above 4200 |
I haven't taken the carb apart and cleaned. Don't have a whole lot of reason to do so...I've ran it multiple days in a row without an issue. No carb adjustments since... I did almost run out of fuel - killed engine before it went dry. Refueled with my spare gas can and off I went with no issues for multiple days. Thoughts on carb? |
|
| Author: | brycecheramie [ Sat Nov 16, 2019 3:13 pm ] |
| Post subject: | Re: RPM drops drastically above 4200 |
I was going to say it sounds carb related to me. could possibly has a slightly clogged jet and when you need more fuel, its not getting it. have you hit anything hard while going down the road? Something that could have messed with carb needle? Intake leak? I'd go to carb first. |
|
| Author: | SlimOx [ Sat Nov 16, 2019 3:58 pm ] |
| Post subject: | Re: RPM drops drastically above 4200 |
Typical county roads and occasional potholes you don't see. Big trailer hops etc... Took a good hit over a river log yesterday but thats typical. Wouldn't I see issues on the lower end if carb was truly messed up? I haven't done anything out of the norm. |
|
| Author: | SlimOx [ Sat Nov 16, 2019 4:02 pm ] |
| Post subject: | Re: RPM drops drastically above 4200 |
Rev limiter? How do they work? Don't they simply keep me at a specific RPM? Not drop me down the 2Ks? Its dropping off once I go over a certain amount of throttle. If I keep it steady below 4200 ish it runs fine... |
|
| Author: | SlimOx [ Sat Nov 16, 2019 4:10 pm ] |
| Post subject: | Re: RPM drops drastically above 4200 |
Recommendations on ways to diagnose/clean carb without a full disassembly? I very much dislike taking the entire thing apart if it isn't the culprit! |
|
| Author: | Russ [ Sat Nov 16, 2019 4:13 pm ] |
| Post subject: | Re: RPM drops drastically above 4200 |
Ugh. Carb basically has three circuits. At idle, it's on the pilot. Past idle it starts getting on the the needle jet. At full throttle it's on the main. In between each theres a transition period where each has its play. If the main is clogged, it can cause there to not be enough fuel when its needed most. If it's doing it out of water, then it could still be the carb. It could also be spark jumping from the boots. Wrap them in electrical tape. Clean the carb. The lower unit isnt gonna cause rpms to all of the sudden drop. The governor isnt the problem either. #CFFITR #GhostBoat #Whoneedsphysicsihaveamudmotor |
|
| Author: | Russ [ Sat Nov 16, 2019 4:19 pm ] |
| Post subject: | Re: RPM drops drastically above 4200 |
Trouble is, unless you take it all the way apart and clean it right, you dont know of it's the problem. That's an easy thing to do, along with checking all fuel connections, making sure theres no water in the gas, etc. The troubleshooting gets harder and more involved (more disassembly) after that. Intake leak is possible, but unlikely since it runs so well up to that 4200 mark. If it's not spark leaking, fuel delivery or carb issue, then do you have an electronic rev limiter? #CFFITR #GhostBoat #Whoneedsphysicsihaveamudmotor |
|
| Author: | Russ [ Sat Nov 16, 2019 4:20 pm ] |
| Post subject: | Re: RPM drops drastically above 4200 |
This sounds electrical with the rpm issues #CFFITR #GhostBoat #Whoneedsphysicsihaveamudmotor |
|
| Author: | SlimOx [ Sat Nov 16, 2019 4:38 pm ] |
| Post subject: | Re: RPM drops drastically above 4200 |
Not spark leaking. Ive checked plugs and they are basically new. Wires are pristine - I did a full replacement last season. I guess I need to start in on the carb. Probably due for a clean anyway. Seems crazy as I've run the boat almost daily with no issue. Only thing that occurred was running out of fuel. Which could lead to bad fuel supply, or as well as plugging a carb up. I have new fuel supply parts on the way. |
|
| Author: | SlimOx [ Sat Nov 16, 2019 4:38 pm ] |
| Post subject: | Re: RPM drops drastically above 4200 |
Not sure how to tell what limiter I have. Will C does all my work - can't get him on the line. |
|
| Author: | SlimOx [ Sat Nov 16, 2019 6:16 pm ] |
| Post subject: | Re: RPM drops drastically above 4200 |
Mikuni disassembly video? I don't think I've done one of these before. |
|
| Author: | jc [ Sat Nov 16, 2019 7:42 pm ] |
| Post subject: | Re: RPM drops drastically above 4200 |
Disconnect the green wire from the rev limiter just to eliminate it and see if that solves your problem. That is if your motor has one. If it's a cdi motor it won't. Just something simple to try. |
|
| Author: | cb5331 [ Sat Nov 16, 2019 8:19 pm ] |
| Post subject: | Re: RPM drops drastically above 4200 |
Shake the gas tank. Sent from my SM-T710 using Tapatalk |
|
| Author: | BlueShamu [ Sat Nov 16, 2019 8:25 pm ] |
| Post subject: | Re: RPM drops drastically above 4200 |
What year and type motor is this? Sounds like rev limiter on 4300 coils...which, if I recall, are 4250. Sent from my iPhone using Tapatalk |
|
| Author: | SlimOx [ Sat Nov 16, 2019 10:12 pm ] |
| Post subject: | Re: RPM drops drastically above 4200 |
2012 gatortail. High rev coils - always ran roughly 4700 at WOT. Gas tank is built in. |
|
| Author: | SlimOx [ Sat Nov 16, 2019 10:34 pm ] |
| Post subject: | Re: RPM drops drastically above 4200 |
35... |
|
| Author: | SlimOx [ Sun Nov 17, 2019 8:05 pm ] |
| Post subject: | Re: RPM drops drastically above 4200 |
Ok....carb cleaned. reinstalled, no change. Fuel pump changed (fuel filter change tomorrow). Still won't get up passed 4200 RPM without losing power. Now, when I WOT from idle it revs high but no propulsion. If I slowly accelerate to 4200 it will get there then rev and lose power (RPM and propulsion). |
|
| Author: | lastchance [ Sun Nov 17, 2019 11:19 pm ] |
| Post subject: | Re: RPM drops drastically above 4200 |
Did you clean needle and seat? Sent from my SM-G975U using Tapatalk |
|
| Author: | Will C [ Mon Nov 18, 2019 12:15 am ] |
| Post subject: | Re: RPM drops drastically above 4200 |
It is one of mine. Cdi motor 4750 coils. I talked to him this afternoon. The symptoms seem odd with that same issue in and out of the water. Probably do a FaceTime |
|
| Author: | SlimOx [ Mon Nov 18, 2019 9:08 am ] |
| Post subject: | Re: RPM drops drastically above 4200 |
Thanks Will! I sent you a text video of the motor running. Same issue thus far. Call me anytime! |
|
| Author: | SlimOx [ Mon Nov 18, 2019 9:11 am ] |
| Post subject: | Re: RPM drops drastically above 4200 |
Yes, needle cleaned etc...the carb was already in good shape - now it is immaculate. Moving on to fuel again...running out of gas makes me consider internal fuel tank issues. Maybe fuel filter or pick-up valve? The tank is built in and I didn't build the boat so a little unclear as to tank internals specifically on this boat. Thanking I may bypass tank and see what happens. |
|
| Author: | SlimOx [ Mon Nov 18, 2019 9:42 am ] |
| Post subject: | Re: RPM drops drastically above 4200 |
Anybody know part numbers (source?) for intake gasket replacement parts? Having trouble getting part numbers to match up. 2012 Briggs 35 carb. |
|
| Author: | Will C [ Mon Nov 18, 2019 10:14 am ] |
| Post subject: | Re: RPM drops drastically above 4200 |
I think your phone doesn’t like talking to mine, lol. No text, vmails etc, calling u now |
|
| Author: | Will C [ Mon Nov 18, 2019 4:56 pm ] |
| Post subject: | Re: RPM drops drastically above 4200 |
Tried to call Slim. The video diagnosed it. Engine is sitting on the coils as I cringe, lol. Must be clutch slipping. The tach only reads 4200 because the coils are limiting the rpm and effecting the reading. Look for grease or anything weird an the clutch disc. I finished that engine march 3 2018. Still sounds good |
|
| Author: | SlimOx [ Tue Nov 19, 2019 9:26 am ] |
| Post subject: | Re: RPM drops drastically above 4200 |
Thanks Will. Call me, I'm available all day. I thought clutch/prop/limiter but my lack of engine knowledge got us here...I looked over the clutch last week but it must need another look. I will talk to you soon. You're spot on....she still sounds great and runs great with this as the one and only exception! |
|
| Author: | Will [ Tue Nov 19, 2019 10:17 pm ] |
| Post subject: | Re: RPM drops drastically above 4200 |
! |
|
| Author: | SlimOx [ Wed Nov 20, 2019 9:41 am ] |
| Post subject: | Re: RPM drops drastically above 4200 |
Any direction y'all can give me on whether or not I remove the clutch entirely or just inspect from the outside. What should I be looking for? Do's and don't of removal? Thanks in advance. |
|
| Author: | brycecheramie [ Thu Nov 21, 2019 6:44 am ] |
| Post subject: | Re: RPM drops drastically above 4200 |
I'm gunna go out on a limb here and say I don't think its the clutch slipping. In my opinion, if it was slipping, your RPM's would INCREASE. I may be wrong and not thinking of something, but that's what I think. If it'd be slipping, it would slip a lot sooner than 4200 rpms, i'd think |
|
| Author: | Will C [ Thu Nov 21, 2019 8:34 am ] |
| Post subject: | Re: RPM drops drastically above 4200 |
I saw a vid he sent. Anytime he hits the throttle it goes to the coils and you see the spray fall. |
|
| Author: | SlimOx [ Thu Nov 21, 2019 9:39 am ] |
| Post subject: | Re: RPM drops drastically above 4200 |
For anyone following - definitely the clutch. Pulled her off last night. The angled arms that attach the clutch wheel to the bearing have multiple cracks and 2 that are broken where they attach. This caused the clutch to spin out of "true" and slip at higher RPMs. So....gatortail sells only the clutch as a whole. $285. Anybody know an alternative? And now that I am done with disassembly...to HELL with removing all that, not fun as most of it was pretty well seized up. Anti-seize here I come. |
|
| Author: | SlimOx [ Thu Nov 21, 2019 9:43 am ] |
| Post subject: | Re: RPM drops drastically above 4200 |
Pics below for those that would be interested later... |
|
| Author: | bluesky2012 [ Thu Nov 21, 2019 9:56 am ] |
| Post subject: | RPM drops drastically above 4200 |
Buy it from gator tail. The gear on the clutch assembly is made specifically by gator tail and is the only place to get it from. They ship it fast, so just buy it, put it on, and go. I had to do that same thing this summer. Sent from my iPhone using Tapatalk Pro |
|
| Page 1 of 2 | All times are UTC - 6 hours |
| Powered by phpBB © 2000, 2002, 2005, 2007 phpBB Group http://www.phpbb.com/ |
|