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Charles, Marine Mechanic
Category: Boat
Satisfied Customers: 3313
Experience:  US Navy (Ret) Certified Mercury Marine Tech with over a decade of repair experience.
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Have twin 275 Verado's. One engine started running rough after

Customer Question

Have twin 275 Verado's. One engine started running rough after fueling. Idled fine but cut out on take off then after plane cut out at around 3800 rpm. Checked onboard filter's and they were clean(had been replaced only a couple hours). Found a mfg mounted filter and changed that. Replaced all stick coils and plugs. On the water hose all seems good until about 3500 rpm and it cuts out. Started other engine and it did the same. Is this something normal they would do with no load? Thinking maybe not enough load for the super charges?
Submitted: 5 months ago.
Category: Boat
Customer: replied 5 months ago.
Also ran compression test. All cylinders were 120 or 122
Expert:  Charles replied 5 months ago.
Hello, my name is***** will assist you.The engines do have a protection system on them to not allow them to rev very high when they are in Neutral. On the engine filters, was the one you changed a red top filter or a snap in filter in the fuel line?
Customer: replied 5 months ago.
I changed both. The mfg filter was hidden and even the Everglades dealer didn't know it was there. I think that was the problem because it looked like it had never been changed. Boat has 500 hrs. I was concerned because it cut out while I was testing with the hose. It sounds great until it revs too high
Customer: replied 5 months ago.
I will splash the boat in the morning and see if that cured it. If not I may need to check back with you.
Expert:  Charles replied 5 months ago.
Was the MFG filter in the boat or on the engine?
Customer: replied 5 months ago.
On the boat. It was a Sierra. It was factory
Customer: replied 5 months ago.
It had a small amount of water in it and tons of rust. Was a 10 micron filter.
Expert:  Charles replied 5 months ago.
There are actually two on the engine. The first is part 19 in this diagram. second is part 31.
Customer: replied 5 months ago.
Yep both were changed just before the problem. I checked both today prior to anything else and they were clean. Dumped them into a glass jar and nothing at all was in them. I think maybe the onboard filter was clogged. You answered my question on the rev limit while in neutral on the hose. All I know to do now is go run it and see. Thanks
Expert:  Charles replied 5 months ago.
Sure thing. If you continue to have this issues, just reply back to this question thread and we can continue.

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