Just wondering if anyone ever had a problem with their motor when warmed up?
Mine runs great up to 6000RPM when cold but after approx. 1/4 mile it falls flat on its face like lack of fuel. then will run at 2000 RPM but going up to 2500 RPM makes it bog down again. I'am getting water peeing out but not as strong as on the F- 50 HP, it penetrates the water 3" and the 115 only hits the surface with bare'ly any force. I'am thinking T-STATT or water pump. any input would be appreciated. It's a 2001 F-115 and it's first time out this year, all fresh gas too..
Thank's, Dave.

Sounds almost like an RPM limiter kicking in. Low oil? Fuel in the oil? Common problem in the Yamaha's. My marine mechanic told me if my '03 "YaMercury ever showed oil above the hashes to definately suck some oil out. He stated that some of the bigger 4-strokes actually had top end difficulties(rpm wise) because of overfull crank cases, and the crank shafts running in oil. I suspect that your thermostat would open well before a 1/4 mile at 6000 RPM's. It's always a safe bet to change the water pump especially if you suspect it's not pumping up to snuff. Have you tried to run it with the cowling off? Maybe check to see if the motors getting hot. Have you been fishing in stained muddy water, or running the boat over sand bars? Sorry I nothing definative for you, but some stuff to think about. .02 Mike

Put in a new water pump, change the oil with the correct oil to the correct level, put in fresh gas, a new thermostat and recheck.

Take care
REW

I vote for the new water pump if you havent put one in by now you are over due.

Thanks for the input , I checked the T-statt in water on the stove and it matches the temp in the service manual. I also pulled the temp sensor and it changes resistence as the water get's hotter so I'am assuming its good, also pulled the connection when motor was running and RPM increased to 800 from 650, cold run mode? I will be trying the water pump next, maybe it is overheating slightly and going into some kind of protective mode? Just a guess ??
Does the oil have to smell like gas for the fuel pump to be bad?, I have read about the bad diaphram's

I will change the water pump and report back.
Thank's, Dave.

I partially plugged the water intake on my 2001 F115 last year while chugging through Burrow Bay on LOW. I didn't know it until I started to pick up speed to move out. The hot motor warning alarm sounded, and the motor shut down to low rpm's by itself. Luckily, no apparent damage was done, the inlet unplugged, and we were on our way. As a safeguard, I did later replace the water pump, it was due. I suggest you do the same. It is time.

Bill Krejca

Just wondering if anyone ever had a problem with their motor when warmed up?
Mine runs great up to 6000RPM when cold but after approx. 1/4 mile it falls flat on its face like lack of fuel. then will run at 2000 RPM but going up to 2500 RPM makes it bog down again. Thank's, Dave.

I had the exact thing happening on my F-115. I discovered the fuel sending line had too much air in the primer bulb. The reason it will run a 1/4 mile is there is enough fuel in the line and bulb to get it going, but then it starves as a result of an air in the line. This happened to my on my first outing of the season too. Even after I pressed the bulb mutlitple times to prime the line it would still occasionally starve. I removed the fuel connector at the engine and pressing the bulb to bleed all the air out and connected the fuel line back to the engine while pushing fuel out the connector. Problem solved!!!

For some reason, I have to bleed the air out of the fuel line at the beginning of every new season? The good news is it is an easy fix!

I would also check for proper venting in your fuel tank. Easy and inexpensive to clean a vent. Plugged vents do what your explaining, but I'll agree it seems like your motor is going into protect mode for some reason.