Outboard runs well until it warms up

[HemiD20]

I have a 1996 50 hp Johnson outboard that runs perfectly when first launching. Once the engine is warm it will cut out at anything above 2400 rpms. It still runs ok at 2400 and bellow while warm. If I let the motor cool back down it will begin running well again until it warms back up. I can replicate this with muffs and while in neutral. ​

 

[HemiD20]

I would like to add that the VRO has been disabled.

I have also found similar issues on other posts with the engine going into a SLOW mode, but everyone I have found never states whether this issue was resolved.

 

[oldboat1]

Better find out how hot it gets -- IR tester at the top of the head. VRO disabled should mean that the harness is unplugged, and you are running 50:1 premix.

 

[HemiD20]

Yes, the harness is unplugged. I’ll try to get a temp later. I have ran it without the VRO for about a season with no trouble, but I know that doesn’t mean a whole lot.

 

[oldboat1]

Will need confirmation, but think the port side sensor needs to be disconnected (for safety, after you determine it is not in fact overheating). Also need to determine at what temp the slow mode kicks in -- maybe 153F? Maybe you are due for water pump work.

 

[jakedaawg]

Guessing you're overheating...better verify that your alarm system is in working order.

 

[HemiD20]

Ok, so this morning I went out and let it run for a while to get warm. I took a temp and it is normal. I have good flow coming from the pisser. I also couldn’t get it to kick back in the slow mode! I’m not sure if that’s a good thing or not since it makes it harder to trouble shoot. I’m thinking you all were on to something with the water pump. It may have had something impeding the impeller and finally broke free. I am going to try and run the thing for a little longer to try a replicate again. I will probably drop the lower unit down either way and check out the water pump just to be safe. Thanks

 

[emoney]

A coil that's starting to fail will displays issues after about 20-25 minutes on the hose or after it reaches temps on the water. If the engine is still showing those signs, and you know it's not overheating, then thats a possibility.