2016 Yamaha F150 High speed/rpm surging

[Weber_67]

I have a two 2016 Yamaha F150's with 20 hours on them.

Boat engines appear to run fine, starting, idle, getting on plane have no issues. But during wot or full speed properly trimmed, the starboard motor will surge or drop down after running for a few.

I will have them around 5k-5.5k rpm and it will drop down and move up and down between 3500-4200, if I back down on both it will settle in and maintain but if I increase the rpm it will surge again.

When I purchased the boat I had a similar issue the first time I took it out, and then it eventually would not even start or idle without stalling, found the main battery connection to the motor was loose, so I assumed it was the same issue.

I did find the other cable was loose this time, but it did not solve the problem.

I'm thinking the next step is to replace the fuel filter to see if that takes care of it.

As far as fuel goes, I only run non-ethanol fuel and the gas is fresh.

Any advice or info?

[TownsendsFJR1300]

When it starts acting up, see if you can squeeze the primer bulb at all.

You shouldn't be able to get a half pump on it. Should you, you have an air leak somewhere before the engine.

As both engines are acting up, is the fuel line coming from the SAME LOCATION /outlet?

Some other possibilities; open the filler cap to see if the tank vent is clogged.

If the primer bulb is defective, (bad internal valve) it can also hamper fuel flow.

If this is a newish engine on an old hull, it's very possible the fuel line internally is coming apart / failing. You'd see a spaghetti / mush inside the cowl fuel filter if it is.


What's your WOT trimmed out?

[Weber_67]

When it starts acting up, see if you can squeeze the primer bulb at all.

You shouldn't be able to get a half pump on it. Should you, you have an air leak somewhere before the engine.

As both engines are acting up, is the fuel line coming from the SAME LOCATION /outlet?

Some other possibilities; open the filler cap to see if the tank vent is clogged.

If the primer bulb is defective, (bad internal valve) it can also hamper fuel flow.

If this is a newish engine on an old hull, it's very possible the fuel line internally is coming apart / failing. You'd see a spaghetti / mush inside the cowl fuel filter if it is.

Problem is only on one engine, brand new boat. Bulb does not lose pressure. WOT trimmed is 5500-6000 depending on conditions.

[TownsendsFJR1300]

Can you run the boat, with the one cowl off while checking the under cowl fuel filter?

Also check that filter for any water inside.

It should stay approx 2/3's full.

Sounds like a fueling issue...

[Weber_67]

Can you run the boat, with the one cowl off while checking the under cowl fuel filter?

Also check that filter for any water inside.

It should stay approx 2/3's full.

Sounds like a fueling issue...

Maybe, running wot and hanging off the back of the boat may be tough.

The boat and motors are under warranty, so I'll take it to the dealer if I don't easily find a solution.

Figured someone may have had a similar issue on a new boat.

[TownsendsFJR1300]

Maybe, running wot and hanging off the back of the boat may be tough.

The boat and motors are under warranty, so I'll take it to the dealer if I don't easily find a solution.

Figured someone may have had a similar issue on a new boat.

The water / fuel filter is at the forward part of the engine. Another body to look or drive would be the way to go.

If it's under warranty, that's really the way to go.

And no, it's not normal...

The clear plastic cup, towards the lower part of the engine is the filter. The RED ring(barely visible) FLOATS if there's water inside:



Yours probably doesn't have the ring but two wires coming off a sensor at the bottom of the cup..



.