2001 OX66 stumbles at idle after running wot

[catchesbass]

This girl runs great on the top end. Really anything above idle she runs great. However, when I slow down to enter a no wake zone or just to idle while graphing the engine stumbles and occasionally dies. She starts right back up. Also, when I first put the boat in the water it starts right up but after a few seconds it coughs and dies. Again, she fires right back up and warms up as normal. ALL the maintenance has been done (VST, lift pumps, etc.) The boat place gave me BR9HS plugs when I have been running BR8HS 10’s in the past. I switched the plugs back to the BR8HS 10’s and it’s a little better but not much. The shop just adjusted the TPS. It wasn’t out of specs but they “made it better” supposedly. This problem was there before they adjusted the TPS. Fuel pressure is within specs, compression is good on all cylinders. I’m thinking of running a BR7HS-10 plug to see if a hotter plug might help since the BR8HS-10’s were a little better than the BR9HS-10’s. Does this sound like something as simple as a hotter plug could fix my issue or do I need to keep digging?

 

[catchesbass]

Rodbolt? Anyone?

 

[myredchevys]

Subscribed- Having the same issues as you-Rodbolt hasn't posted here in some time- I would advise not going to a BR-7 plug- 2 strokes do not like detonation and you are going with to hot of a plug- did the shop sync and adjust the linkage-possible some bad fuel? Keep us posted

 

[napkinthief]

any updates on this? this happened to before, but far in between incidents... it happened to me twice this past weekend circling to get on the fuel dock would love to have a steady low idle

 

[catchesbass]

Fellas I’m so sorry about dropping off the planet for a while. I was in the hospital then we had deaths in the family. Not to mention a good case of Covid. Anyway, this issue still persists. I did get some improvement after cleaning a really dirty fuel pressure regulator screen but that was minimal. I did end up changing the oil pump as the line large was hanging up. I guess it finally wore out after 22 years. But I still can’t get a good steady idle. I haven’t changed the tps but that’s next. I’ll grab a used one. Gotta be better than what I have. I use my boat all year every year several days per week so even a used part it’s probably way better than what I have. Tomorrow I’m going to check the fuel pressure regulator screen and see if it’s clogged again. Especially after changing the oil pump. It’s so crazy. My boat runs so good anywhere above idle. But idling is just a mess. I’ll get her fixed someday. I’ll keep testing and tinkering until I figure it out.

 

[99yam40]

strange, 3 years and still no one has a clue what motor you have

 

[catchesbass]

strange, 3 years and still no one has a clue what motor you have

It’s in the title

 

[99yam40]

How many different OX66 did Yamaha produce in 2001?

every one of them should have a model # on the bracket.

 

[catchesbass]

It’s a VX200TLRZ

 

[99yam40]

Fellas I’m so sorry about dropping off the planet for a while. I was in the hospital then we had deaths in the family. Not to mention a good case of Covid. Anyway, this issue still persists. I did get some improvement after cleaning a really dirty fuel pressure regulator screen but that was minimal. I did end up changing the oil pump as the line large was hanging up. I guess it finally wore out after 22 years. But I still can’t get a good steady idle. I haven’t changed the tps but that’s next. I’ll grab a used one. Gotta be better than what I have. I use my boat all year every year several days per week so even a used part it’s probably way better than what I have. Tomorrow I’m going to check the fuel pressure regulator screen and see if it’s clogged again. Especially after changing the oil pump. It’s so crazy. My boat runs so good anywhere above idle. But idling is just a mess. I’ll get her fixed someday. I’ll keep testing and tinkering until I figure it out.

not sure what the changing of the oil pump has to do with your problem or what the line large hanging up is about.

Or how changing the oil pump would affect the fuel pressure regulator screen.

monitor the fuel pressure to see what it is doing when the problem shows up.
moving the throttle changes the vacuum to the pressure regulator and should modify the fuel pressure it puts out for the changing load on motor.
sending the injectors to be cleaned and tested may be a good thing to do.
along with checking the VST screen.
have you drained the VST to make sure no water or other trash comes out?

 

[catchesbass]

The oil pump linkage itself wouldn’t spring back. This was causing over oiling. It effectively held the throttle plates open more than they should be. The idle would occasionally hang at higher rpm’s. Changing the oil pump fixed this. I disassembled the oils pump and sure enough the little “crankshaft” inside the pump had one edge completely work off. Replacement pump works as it should. However, a replacement NEW pump was $300 so I got a used one. No idea what could have been inside the used pump as far as debris. The injectors were cleaned and flow tested about three months ago. Upon first start up everything works as it should. It’s after a run when things go south. Today I’m doing yet another VST service and I’ll check that pressure regulator screen again. If I don’t find anything suspect in there I don’t know what else I can do with the tools on hand. I forgot to mention that I did replace the electric fuel pump last year. I got a really good deal on one so I figured what the hell. Can’t hurt. It made zero difference.

 

[99yam40]

Oh, so the line large was suppose to be linkage.
the pressure regulator can be tested to make sure it does its thing correctly

 

[catchesbass]

Sorry. Autocorrect got me

 

[catchesbass]

VST and fuel pressure regulator screen was super clean. Not even a speck of dirt. I guess I’ll just take it in next week

 

[catchesbass]

It seems that somehow the linkage from the throttle plate to the oil pump linkage was binding keeping the throttle plates partially open. It was hard to track because it didn’t happen constantly. I found this myself after the shop said it was good to go. Now I have to readjust the oil linkage rod and the idle speed. That should be easy now that everything is working smoothly. I’m not completely sure how I fixed it other than completely disassembling everything thing and reassembling it like a normal link/sync. I’ll keep an eye on it