Yamaha F150 Low RPM

[nymart]

I have a 2005 Yamaha F150 on my 191FS. I used to run around 32-24 MPH at WOT and 5000 RPM. The RPM and MPH started dropping last week and I found that my fuel filter was really nasty so I replaced it. I also changed from the stock 19" pitch prop to a 15" as I was hoping for a better hole shot. I tried it this weekend and I do have a better hole shot but instead of my RPM going up as expected, I am maxed out at 4000 RPM and only getting up to 24-26 MPH. Any suggestions as to what might be causing my lack of power?

[Deker]

i started w/ a yamaha F115 on my 195cc and a 15 pitch and I got too many RPMS. I called the Triumph factory and spoke to the engineer and he said with that engine i should have the 17 pitch prop. i suggest you do the same, they were very helpful.

[saltydawg]

fuel pick up might be a bit trashed also if the filter was nasty, also if the filter has been clogged up some trash may have gotten thru and fouled the plugs, a fuel system flush may be needed. there may be residual trash in the tank

[Ron's 195DC]

It's got to be something like what Saltydog suggests. Maybe the bad fuel filter is an indication of what the fuel pick-up is like, or a kinked fuel hose or something.

I have the 195DC which is a bit heavier (on paper) than your 191Fs. I run a 150 yamaha 4s as well. I have a 14 1/2 x 17" pitch aluminum prop on mine and she'll do an honest 45-47 mph at 5800 rpm with two people and about 45 gallons in my 60 gallon fuel tank.

Has to be starved for fuel in some way.

Ron

[Mud Runner]

Even with a 10 micron fuel/water separator, some stuff gets by. One item that needs to be serviced that might cause you low RPM's is the VST filter. On the port side under the intake induction tubes is the VST tank. The high pressure fuel pump is in the tank. At the base of the pump is the screen that is the size of your pinky nail. To get to it you have to remove the tank and open it. You'll need a new O-ring type gasket. The screen can be clean with solvent and blown with high pressure air. Here's a view of the tank and components.

http://www.boats.net/parts/search.ht...JECTION+PUMP+1

[nymart]

Just thought I would post an update as a warning...I took the boat in for service. They initially found the problem to be both the screen that Mud Runner spoke of and one fuel injector that needed to be replaced. They replaced the one and saw some improvement but now they are saying that all 4 need to be replaced. According to the dealership, this is a common problem and that Yamaha (in their experience) doesn't cover it under warranty. So I am about to drop $1500 into a 2 year old engine (under warranty) with very low hours....I will be contacting Yamaha myself today, but the dealer says they probably won't budge....

[rivahboy]

Do you have your boat serviced reg. by the dealer? The only reason I ask is would that make a diff. on them standing behind the warranty? I try to get mine serviced by the dealer mainly if there is a warranty issue I can atleast say I did my part. But I must say I would be very upset to say the least. Please post an update if you dont mind I am very interested in the outcome. Warrantys...its like insurance....they are always there to sell you the policy but when you need help they always try to wiggle out. This is the kind of thing you make note of so when you buy your next boat you know what engine to put on it.

[NCangler]

How can that not cover a problem with the engine under their warranty? This is a new one on me. I would contact Yamaha too as you are doing and I would ask for an explanation of the problem and why it is not under warranty fromt the dealer.

[nymart]

Thanks. Haven't contacted Yamaha yet as I got the boat back late on Friday and have to wait until Monday (I didn't have the serial numbers handy and Yamaha needs them to have a conversation). I will post the results of my conversation.

[nymart]

Just got off the phone with Yamaha and as expected, they blame the ethanol. According to them, they have no control over fuel quality and as such the warranty does not cover clogs and corrosion. Now I have read enough about ethanol to understand its potential effects, but given that I have a plastic boat with a plastic fuel tank, the ethanol isn't corroding my fuel tank and if the injectors are so sensitive that they can't deal with a little debris (you will never get truly clean fuel) then that seems like a design flaw to me. At least I am back on the water now, but if you haven't put at least one (or more) external fuel filters on your boat, spend the money...as you can all see the damage is WAY more expensive...Thanks

PS..the grand total for both engines (my 9.9 kicker needed a whole new carb) was $3K...