No high rpms 15 hp four stroke 2001

[captaindarrell]

I recently posted about a diaphragm issue. Hopefully I did not alienate too many users. We are currently in transit and the motor is on our tender. Taking it to a shop is not on our schedule.
The motor does start and idles just fine. I can't get high rpms in or out of gear.

I can purchase more parts when we land in port. Where do I start?

Fuel pump, a computer chip or other module. Or higher octane gas.
I was able to get higher rpms when I ran Valvtect into the fuel line. But that was only momentarily.

I changed out hoses. Should the bulb primer stay hard all the time? Mine might not be doing that. I don't want to throw too much out there and confuse the issue further. I have changed all the parts in my main carburetor and my backup.

[boats.net]

Need to run a compression test and check for spark at spark plugs but sounds like the carb needs to be cleaned.

[captaindarrell]

Thanks
Where can I find the 12mm fitting for a comp tester? napa has a rubber tip-
I assume that will work? What should the proper reading be for F15mshz?

I tested engine in a Barrel. I am really shooting oily junk out the exhaust.
Tried seafoam. Still no high rpms.
Next step will be the compression test. Pretty sure the carbs are clean.
I swapped out my spare.

Thanks

[captaindarrell]

Forgot to mention- my plugs are extremely oily. I also might be making oil.

[captaindarrell]

Compression test completed- 165 both plugs. Plugs are extremely black and carboned up. I also smell fuel in the oil. Any more ideas?

Thanks

[rodbolt17]

take the fuel pump off leaving all lines attached, pump the bulb up hard.
if no gas leaks out the back of the pump reinstall it.
then check ign timing at the problem RPM for proper advance.

[captaindarrell]

I tried taking the pump off and squeezing the bulb.
She leaks quite a bit. Can she be temporary repaired until I get a new One. I will have to order and ship to next port. Thanks Darrell

[Teamyama]

rpm loss

Hello Captain, i have the same motor -The plugs are black-she's too rich.If you have cleaned out the carby and still rich adjust the air screw on carby . To get the best mix , turn in screw(there might be a cover over it)until lightly seated,unscrew about 1 and a half turns) warm up engine, screw in slowly until motor coughs and now unscrew until it coughs again.count the number of turns of screw between both spots and go back halfway.this is the optimum setting!! hope that makes sense. Yamaha head office told me this. Does it die if you go full wot or just struggle for power?? Good luck.

[99yam40]

I tried taking the pump off and squeezing the bulb.
She leaks quite a bit. Can she be temporary repaired until I get a new One. I will have to order and ship to next port. Thanks Darrell

Nope, no way to fix without replacing.
Make sure you change the oil also as it does not lubricate as well when thinned out with fuel and you may cause major problems if you keep running it like that

[captaindarrell]

Thanks Guys-

Here is the latest update. I installed a new fuel pump. Still doesn't want to give me power. Hopefully that will stop me from making oil. She starts just fine and doesn't stall out. I have two carbs and cleaned them both. I am getting a little fuel leak on the bottom of the carb. I already changed out the diaphram on the carb. Can any body point me to where this adjustment is on the carb for richness? What cover are you referring to. The F15mshz is a pretty simple carb. She doesn't die when I go to WOT- just struggles! Checked Compression once again and getting 162 in each cylinder. I won't give up on this. Trust me. What about the suggestion of timing being off? Thanks for all your help. I am sure most of these problems are related to many years of using Ethanol fuel. There isn't much room for error in these small engines.

[captaindarrell]

Guys- The problem has been resolved for the no power issue. I did a really dumb thing when putting the carb back. Wrong part/wrong place. really stupid! I appreciate all the responses. Still have a small carb leak issues - I cant find the part number for the two small O rings next to the diaphram. not on the parts schematic. Also I have know clue where the adjustment screw for the richness issue on this motor (teamyama suggestion). Lets verify that we are talking about the same motor Thanks