Help with my motor

[IA4PATS]

I bought a boat with a 2003 Yamaha 115 four stroke. It doesn't seem to run very well. I know the gas was pretty old so I sucked that all out and replaced it with added Seafoam. It stills runs kind a bad. I put all the power to it and it doesn't have the power to even get on plane. It seems to rev up good in neutral, but not in gear. Do I need to run it more to get it cleaned out? Also, it has this thing on it. Could this restrict it that much?

[h8go4s]

I'm no expert, but that I don't think that rock guard is the total problem. Still, I'd yank it off and see if that helps. It's only half a dozen bolts at most, can't be too difficult.

I'm also wondering if they downsized the prop to fit it inside the rock guard. Ask a Yamaha dealer what prop is recommended with that motor and boat. You'll probably need model numbers for both.

[tazimna]

not sure if it's on all yamahas, but on my 2000 2 stroke, if the oil resevoir is under half full, it does exactly what you describing. Taz

[TR21HP]

You should be running a 13x17 prop according to the Yamaha spec site. That's a stainless steel prop.

[RebelSS]

Being a 4 stoke, and it's had old gas, no power under load, I'd first look at fuel delivery issues, as in clogged jets,etc. I'd go through and thoroughly inspect/ clean the carbs and fuel system, replace fuel filter, and go from there.

[bassfshin24]

I would also check spark plugs and make sure they are clean or just replace the spark plugs. I have a 2 stroke Merc but had an issue last spring where it had a hard time getting on plain and then would only run about 35-40mph full throttle compared to 58-64mph full throttle. Spoke with a buddy and he said your spark plugs could be fouled up and to replace them. Replaced them and went out and that baby got on plain in 2 seconds.

[Dragonsm]

I have the same year motor on a 17 1/2 superhawk and ran into similar issues last spring when I bought it.

Prior owners left me with a full tank of old fuel and when I initially ran it, it had some hesitation and max RPM's were only about 5,000.

Besides changing out the prop (went with the 17 pitch Yamaha OEM white Alum prop) I also changed all the plugs, and cleaned out the fuel filter mounted on the motor.

Along with a half tank of fresh fuel, and some Yamaha ring free, the motor really woke up for me and now I am hitting 6,000 rpms.

Night and day difference.

The above stuff is pretty cheap, so I'd at least give that a shot.

[marine_man]

Do you have a tachometer on the boat? What are you getting if you do?

marine_man

[DREZLER]

Had the exact same problem on rainy river last year in my buddies boat with the same motor. Revd up fine in Neutral but no power in forward.

We were ready to scrap the motor and sell the boat. It ended up needing new plugs and ran perfectly.

[Dragonsm]

Initially when I pulled the first plug in my motor, it was black with carbon.

The others shared about the same look.

If this is your first Yamaha product, from everything I have learned so far with an outboard and also a snowmobile of theirs....they LOVE NGK sparkplugs - LFR6A-11 for the F115.

If you didn't get a manual with your boat, it can be easily had online in PDF format which will give you all the information.

Steve

[IA4PATS]

Well, I sucked out all the gas and replaced it with new gas and some Cheveron injector cleaner and Seafoam. I also replaced the fuel filter and spark plugs. We took it out this morning. The first couple seconds it ran a little rough and then went pretty good, but not great. Got up on plane, or is it plain... anyway, running about 20mph and 3500 rpms. went for about five minutes and then it started to bog down again. by the time we got back to the dock area I was doing about 6.5 mph at 1800 rpms. It is now parked at a shop.

[Dragonsm]

Sorry to hear about your motor....hopefully it turns out to be something small and inexpensive.

If you don't mind, I'd be interested in knowing what the repair shop ends up finding out the issue is as it may be something I would possibly encounter in the future.

Good Luck!

Also, if your trim gauge ever stops working/reading correct trim....just hit me up....I ran into that issue with the motor shortly after I got it and after pulling my hair out over it...was finally able to track down the issue to the motor being a simple trim tab ring....original one was plastic...new one is metal (about a 10 dollar part) and it was quite a simple fix.

[gunner55]

Been having this issue with the trim gauge for a while.Wasn't going to fix as it's pretty easy (sound/rpm's) for me to tell when it's trimmed correctly but if it's a simple & cheap fix I'll give it a shot.Thanks for you help Dragonsm

[Dragonsm]

Going off memory here, but it looks almost like a hose clamp strapped on the horizontal shaft in front of the motor...(where it pivots/tilts) I want to say it was on the left side while sitting in the boat looking back on the motor and you will need a short screwdriver to remove the mounting screw.

The original piece that came with the motor were plastic and broke. If you do an internet search you will find plenty of stories and solutions...etc

It may not be the culprit, but it is a common issue with the original part.

Good Luck and hopefully that is what it is.

[Cliff Wagenbach]

If your motor is a four stroke it is probably the fuel injectors. That year was bad for clogged injectors! I had to finally install an in-line fuel filter, ahead of the motors filter to solve the problem of clogged injectors.

Cliff

[delcecchi]

I think that is a good Idea. I put one of those canister fuel filters on my boat too, just in case.

[gunner55]

Been having a few low idle fuel issues too(02/03 115).Nothing real serious but going to look into putting a filter in line.Thanks guys