Yamaha 2009 40hp 4 stroke issue

[Chiflyguy]

Seem to have lost 5-6 mph lately.
Haven't checked the prop for a ball of fishing line yet, bought a new fuel/water separator filter I have to change, blah blah blah
Tilt and trim are operational.
Did recently fill up at a Marina
Anyone have a tip.
I have done 0 troubleshooting at this point.

 

[WTM]

measured how? instrument panel or gps?

 

[Chiflyguy]

measured how? instrument panel or gps?

GPS on the graph
I know solo I get 27 or 28 mph
Last two trips out, 22 or 23

 

[BigCityBubba]

Does it take longer to get on plane? If it does, have you pulled the drain plug lately? That seems like a silly question but there are people out there that never pull their drain plug which is why I ask. Is there anything else that may have caused your boat to gain weight? If you have a tach, you should see that you aren't getting the rpms that you once did.

 

[Pilchard]

If nothing changed and your motor is just being a slug, I'd guess you are in for all new filters and getting your injectors cleaned.

 

[Chiflyguy]

Does it take longer to get on plane? If it does, have you pulled the drain plug lately? That seems like a silly question but there are people out there that never pull their drain plug which is why I ask. Is there anything else that may have caused your boat to gain weight? If you have a tach, you should see that you aren't getting the rpms that you once did.

Gonna go in the morning and do some troubleshooting.
Got some Star Tron Fuel Treatment and a new Yamaha fuel/water filter.

 

[Chiflyguy]

If nothing changed and your motor is just being a slug, I'd guess you are in for all new filters and getting your injectors cleaned.

It's in a slip so I'll probably end up trailering it to see what's what.

 

[Chiflyguy]

Does it take longer to get on plane? If it does, have you pulled the drain plug lately? That seems like a silly question but there are people out there that never pull their drain plug which is why I ask. Is there anything else that may have caused your boat to gain weight? If you have a tach, you should see that you aren't getting the rpms that you once did.

Not really.
I did notice that there's more "splash" on the side of the boat even when I'm at full throttle.
Got a tack but don't remember what full throttle was before..

 

[Doecrusher]

Water logged maybe since you said it's at a slip???

 

[WTM]

have you added any weight up toward the front of the boat, ie batteries, gear etc?

 

[Tenntrapper]

Not really.
I did notice that there's more "splash" on the side of the boat even when I'm at full throttle.
Got a tack but don't remember what full throttle was before..

More "splash" sounds like extra weight in the front. You've been in my boat. If daughter is sitting in front, it moves the splash line forward considerably...as opposed to sitting in the back. It also reduces top speed by a few mph.

 

[Pilchard]

I'd inspect the bilge. See if it's got water in it

 

[Chiflyguy]

I'd inspect the bilge. See if it's got water in it

Had 30 seconds of pumping worth.
Changed the fuel/water separator this morning.
No dice.
Got a Yamaha Mechanic gonna look at it on site.
Just don't have time.

 

[hillbillyfab]

What about plugs? I had an outboard that had less than 20 hours on it, performance was suffering. I changed the fuel, then the fuel filters and finally convinced myself plugs were cheap enough to replace…Bam back in business all for the expense of 3 spark plugs.

 

[Chiflyguy]

What about plugs? I had an outboard that had less than 20 hours on it, performance was suffering. I changed the fuel, then the fuel filters and finally convinced myself plugs were cheap enough to replace…Bam back in business all for the expense of 3 spark plugs.

My engine knowledge is minimal.
I just don't have time.
Work and my other stuff gets in the way.

 

[Chiflyguy]

Had a "mechanic" look at it.
Plugs got spark, changed plugs, all cylinders at 150 compression, new fuel line, new water fuel separator, did an oil change while there, inspected prop.
Motor at 5150 rpm which is good but still seem to have lost 3-4 mph.
He told me for $100 per injector, Yamaha will clean and flow test.
How much are fuel injectors?
Also, here's where we got into a little disagreement.
I asked the guy if he's sure it's not or the tilt trim. He said if it was the prop, the rpm's would change on the gauge.
Now I'm no boat mechanic obviously, but where does the rpm get measured,on the prop?

 

[MickThompson]

Had a "mechanic" look at it.
Plugs got spark, changed plugs, all cylinders at 150 compression, new fuel line, new water fuel separator, did an oil change while there, inspected prop.
Motor at 5150 rpm which is good but still seem to have lost 3-4 mph.
He told me for $100 per injector, Yamaha will clean and flow test.
How much are fuel injectors?
Also, here's where we got into a little disagreement.
I asked the guy if he's sure it's not or the tilt trim. He said if it was the prop, the rpm's would change on the gauge.
Now I'm no boat mechanic obviously, but where does the rpm get measured,on the prop?

If the trim is bad, it won't move. If it's moving without you moving it, you'll hear/see the rpm's change. Once I'm on plane at WOT, I gain rpm's as I trim the motor back/up. Down/in will lower the rpms. If the prop hub is "spun", you'll see a rpm spike when it slips and the motor over revs.

Basically the loading on the propeller changes how fast the motor turns

 

[Chiflyguy]

If the trim is bad, it won't move. If it's moving without you moving it, you'll hear/see the rpm's change. Once I'm on plane at WOT, I gain rpm's as I trim the motor back/up. Down/in will lower the rpms. If the prop hub is "spun", you'll see a rpm spike when it slips and the motor over revs.

Basically the loading on the propeller changes how fast the motor turns

Well, the tilt/trim works just fine then.
All this started when I bought gas at a marina.
Might just run it out and fill up from cans next time.

 

[Tenntrapper]

Had a "mechanic" look at it.
Plugs got spark, changed plugs, all cylinders at 150 compression, new fuel line, new water fuel separator, did an oil change while there, inspected prop.
Motor at 5150 rpm which is good but still seem to have lost 3-4 mph.
He told me for $100 per injector, Yamaha will clean and flow test.
How much are fuel injectors?
Also, here's where we got into a little disagreement.
I asked the guy if he's sure it's not or the tilt trim. He said if it was the prop, the rpm's would change on the gauge.
Now I'm no boat mechanic obviously, but where does the rpm get measured,on the prop?

The max WOT throttle range for your motor is 5-6000 rpm. You are within the range, but on the lower end. You may have gotten some bad gas...if nothing else has changed....weight distribution, etc.
You may want to run some sea foam through it. Wouldn't hurt to try it anyway.

 

[Tenntrapper]

Next time you go to Morristown, take your gas can with you and go by the airport and get 5 gal of 100LL to run through it.
They will let you buy it as long as it goes in a jug...can't dispense into you car, etc. It has some lead in it.


BTW....it's 7.66 per gallon today.