Yamaha 2009 40hp 4 stroke issue

Chiflyguy

Chiflyguy

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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.
 
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.
 
BigCityBubba said:
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.
Click to expand...
Gonna go in the morning and do some troubleshooting.
Got some Star Tron Fuel Treatment and a new Yamaha fuel/water filter.
 
BigCityBubba said:
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.
Click to expand...
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..
 
Chiflyguy said:
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..
Click to expand...
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.
 
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.
 
hillbillyfab said:
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.
Click to expand...
My engine knowledge is minimal.
I just don't have time.
Work and my other stuff gets in the way.
 
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?
 
Chiflyguy said:
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?
Click to expand...
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
 
MickThompson said:
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
Click to expand...
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.
 
Chiflyguy said:
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?
Click to expand...
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.
 
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.
 

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