Yamaha F115 Performance Issues

[Captain-B]

Hello fellow boaters. I am having some issues with my 2004 Yamaha F115TR (4-stroke) and could use some good advice. The motor came on a 2004 Sea-Pro 180cc that I bought last year. The only thing that was not stock on the motor was the prop (13 x 19 instead of the lower pitched 13 x 17).

She ran at about 5800RPM WOT and had a top speed of about 40mph. My only issue was that it took about 10 seconds to get up on a plane, but I figured that was probably caused by the prop pitch combined with the 4 stroke's weight in the back.

Last week I was headed off-shore with some buddies to slay some Amberjacks when the boat suddenly started to lose it's plane. The engine sounded like it was bogging a bit, the rpms dropped and the boat slowed to about 15 mph at full throttle. We turned around and started to idle back. Once in the harbor I wanted to see if the problem had gone away and to my suprise it had.... for a minute. Then it happened again.

Technically this is not the first time that this has happened. Once before the same thing occurred and the dealer claimed it was dirty fuel injectors. He blamed it on Sea-Pro not installing fuel-water separators on their boats. So, one fuel-water separator and $400 dollars later I had my boat up and running again.

So this will be the second time this has happened in a 6 month time-frame, however the tests that diagnosed the problem last time are now showing up negative. Last time the technician removed one injector connector at a time while idling which revealed a dead cylinder, and this time when I did the same all appear to be running fine. I have a clean fuel filter, a brand new fuel-water separator, the primer bulb is always full of pressure and my plugs are in great shape.

Oh, one last detail. When the problem occurs on the water, giving the engine full throttle pushes it up to about 3000 rpm and that's all it has. However if you pump the throttle once or twice it will gradually increase until it gets up on a plane. The funny thing is that you have to keep pumping otherwise it will eventually die back down. What the heck is going on?

Could this be anything but clogged fuel injectors? Why would this happen again? What is the best way to diagnose and fix this problem without spending a fortune and how can it be prevented from happening in the future?

Any help is greatly appreciated.

 

[David Greer]

Re: Yamaha F115 Performance Issues

sounds like something is tripping your devices that slow an engine to prevent damage, such as with low oil or overheat. I assume you are not hearing/seeing alarms, which means either the speed arrestor is malfunctioning, or the alarms are. My skill level won't let me go much farther than that.

 

[rodbolt]

Re: Yamaha F115 Performance Issues

check the filter between the VST and the mechanical pump,if one was installed.
then check the filter in the VST.
your describing a classic VST filter restriction.
when you rapidly accelerate the injectors not only fire in sequence they also fire asynchroniously, means you have sequential and group injector fireing.
this is an "accelerator" pump.
adds extra fuel to compensate for the additional air when the throttle shutters open rapidly.
can be quicly tested with test wheel YB-1624 and the fuel pressure test guage.
test should take maybe 10 minutes.
if your shop doesnt have the proper test equipment AND school certs on the wall for fuel,four stroke and advanced 4 stroke, find another shop.

on your prop, add or enlarge the vent holes just fwd of the blade roots.
if it was an alarm condition you will see about 2000 RPM and thats about it.

 

[Casco Bay Outrage]

Re: Yamaha F115 Performance Issues

Capt-B -

Follow Rodbolt's advice. He is a master Yamaha mechanic.

Your problem has been posted about several times this year, and by me last year.My thread

I think my repair bill was more like $400, not the $600 I said in the post.

 

[Captain-B]

Re: Yamaha F115 Performance Issues

I figured that it would be a fuel/clog issue. The shops in my area are booked through May so I'm going to take a peek at the vst filters myself. I have the service manual and have noted the instructions on your other posts so it shouldn't be to tough. I really appreciate the advice and will let you know what I find.

Oh, one question for rodbolt. What exactly do you mean by "add vent holes" to your prop? Anywhere I could see an example? Using aluminum currently. Saving up for stainless.

 

[rodbolt]

Re: Yamaha F115 Performance Issues

on the prop issue,
start a new thread on the prop forums.
Dhadly and a few others are very knowledgable with props and venting them.

 

[Captain-B]

Update - Yamaha 115 performance issues

Update - Yamaha 115 performance issues

Hey guys here's an update. Being that the local shops have no availablilty this month I decided to do some of the checks that Rodbolt had recomended.

First check was the filter between the VST and the mechanical pump. It appears to be a paper-element filter and a replacement is on the way from Yamaha. I flushed it out hoping to remove any crud, however I doubt this is where the problem is.

Second check was the VST filter, and let me thank you again Rodbolt for the advice. It took me and a buddy about an hour and a half to disassemble the manifold and VST and only about 45 minutes getting everything back together. There was a very small amount of crud in the tank ( I mean very small, almost none ) and the filter covering the high pressure pump appeared clean. So, I don't believe the problem was here either however I am glad I learned how to check it if needed.

Last I completely replaced my fuel/water seperator unit with a new one with a larger filter. The last one was a pain to remove and was hard to find in stores. I understand that they should be changed about once a season however the through-hull vent on the side of the boat was broken for a period of time and I'm sure that some water must have weaseled its way into my gas tank.

I am taking the boat out today for a test run to see if any change in performance can be felt.

 

[Captain-B]

Problem Still There - Yamaha F115 Performance Issues

Problem Still There - Yamaha F115 Performance Issues

Took the boat out and was excited to feel her perform like she should. It took seconds to jump up on plane and cruised beautifully at 4800rpm at about 30 mph.

However, after about 10 minutes, I started to hear a change in the tone of the engine. The rpms started to fall slowly until it started to bogg at about 1500 rpm which is when I pulled back on the throttle. After that, with pumping, I couldn't get her up past 3500 rpms. Without pumping it would just loose rpms until the boat was barely moving. I opted to take it easy and idle back.

Any other advice guys? I cant believe she ran so well for about 10 minutes only to do the same thing again. What would cause the problem to occur after a few minutes of driving and not right away? The only thing I can think of is

A) the tank has a large amount of water in it and after a few minutes of driving the water mixes in with the gas and causes the problem.

B) Problem only occurs when the engine is hot. Even though I idled around for 10 minutes prior to taking off could the engine be overheating at higher rpms? If so I'm not getting any warnings.

Any more advice would be great!! Thanks

 

[cousinabe]

Re: Yamaha F115 Performance Issues

try an auxiliary fuel tank/supply to isolate the issue.

 

[Casco Bay Outrage]

Re: Yamaha F115 Performance Issues

We need to back up a bit.

You bought the boat last year. Was the boat stored over the winter with regular gas or ethanol blended? Was there any fuel treatment used?

When you changed the separator filter, what did the contents of the old filter look like?

Have you checked the new filter? Dump it into a glass container.

If there is ethanol blended fuel left untreated it will seperate and the engine will run like poo.

If there is bad gas in the engine, you need to drain everything out of the engine, fuel lines and tank.

Additionally, you mentioned you cleaned the VST, and replaced filters. Have you had the injectors cleaned? They should be sent to a professional shop. Costs about ~$25 injector + shipping.

An engine at idle has no load and will may not show the problem. My fuel system issues 2 years ago occured only when trying to go over 1700 rpm's.

Remember to treat every tank/fillup of fuel with a stabilizer.

 

[Captain-B]

Re: Yamaha F115 Performance Issues

Casco Bay Outrage,
Thanks a bunch for helping me with this issue. Your advice is greatly appreciated.

To answer your questions.

I live in Charleston, SC. Until now the boat hasn't stayed dry for longer than a week or two. My buddies and my wife and I are pretty avid fishers and go out all year round so I have not winterized the boat because it is continuously used at least 2-4 times per month.

As for the contents of the fuel water separators, nothing out of the ordinary. Perhaps a very small amount of brown particles, but nothing too concerning. When dumped into a glass and left alone for an hour or two there is no apparent separation of gas and water.

The injectors were sent away to be cleaned 3 or 4 months ago when the problem first occured. However that issue was diagnosed by removing the electrical connections from the injectors while idling and realizing that no apparent change was noticable on one of the cylinders (meaning that it was clogged). Now it appears that all injectors are equally good (or bad).

I also do use fuel stabilizer during every fill up.

I hope this helps a little. Your comments are appreciated.

I am going to go back out real quick with a separate fuel tank and try it out. Keeping my fingers crossed!

 

[jay00f4]

Re: Yamaha F115 Performance Issues

This is the exact scenario I have. I did everything you did and have the identical issue. I am going to take it all back apart again and see if I see anything in the vst tank or pump.

Please post up whatever you find and I will do so as well.

 

[Casco Bay Outrage]

Re: Yamaha F115 Performance Issues

While far from an expert, I have had this engine problem and have since followed dozens of threads regarding bogging, rough running on Yamaha's so I can learn.

I have read, from Rodbolt's posts and others, that it occasionally takes 2 or more cleaning/inspections to get the crud (or whatever it is that is causing the clogging) out. Just like those with carb issues.

Going through the system with a methodical approach works best, rather than willy-nilly.

Looking forward to hearing Capt B's report.

Jay - Is your issue identical? Have you ruled out bad fuel, filters and cleaned the VST?

 

[jay00f4]

Re: Yamaha F115 Performance Issues

Yes! my issue is identical and I have completed everything he has to have the same symptoms.

I have replaced all filters, removed the VST and cleaned, replaced mechanical pump, cleaned injectors(twice) pumped tank dry and replaced with fresh fuel.

 

[southtexas]

Re: Yamaha F115 Performance Issues

Sorry to jump into your thread but just curious--what fuel stabilizer do you guys use for this motor? that's all, thanks!!

 

[jay00f4]

Re: Yamaha F115 Performance Issues

I use the marine sta-bil for ethanol gas.

 

[Casco Bay Outrage]

Re: Yamaha F115 Performance Issues

I use Stabil as well year round. Even if you don't have ethanol yet, I strongly recommend a 10 micron water separator and a stabilizer.

Jay - When you said you cleaned the injectors twice, was this a DIY or did you have them sent out? While I have read that DIY cleaning can help, the professional shops use ultrasonic machine, do a flow test etc.

Hmm...

 

[jay00f4]

Re: Yamaha F115 Performance Issues

First time I sent them out and had them professionally done for $75 each. Last time I did myself.

I took it all apart again on Saturday. VST filter clogged again. I have a 10 micron yamaha water fuel seperator and an new filter on the back of the motor. Frustrated with how this was happening I decided to replace all the fuel lines. I put it all together and replaced the lines. Boat ran great all day on Sunday. I am keeping my fingers crossed that it is finally fixed.

 

[Captain-B]

Re: Yamaha F115 Performance Issues

Interesting.... so it ran all day eh? Please do another post when you go out again and let us know if the problem is solved.

I wouldn't doubt that I am having the same issue. Yesterday I hooked up an auxiliary tank, installed the new inline and regular filters, and took her for a spin. At first she was having the same issue but then it suddenly picked up and ran like a champion. I drove around the launch at cruising speed for about 2 minutes thinking that my problems were solved but then it died down again. I gave it a little gas, and the engine started vibrating like hell. This is new, and I think that it is about time to throw in the towel and wait two more weeks for the first available shop to check it out for me. If I buy one more part and find out it didnt work I'm going to &^*% a brick!

Hey Jay00f4, how much did the new hoses set you back? The two filters alone were 90 bucks! After taking off the manifold to clean the vst I know that there are a ton of hoses in there, or did you just change the main line from the tank, the bulb, from the filter to the pump, and the line to the vst? If thats the case then it should only have been a small fortune.

Thanks for all the replies guys.

 

[jay00f4]

Re: Yamaha F115 Performance Issues

I only changed all the hoses on the boat itself leading to the motor. There was 1 from the tank to the water/fuel seperator, form there to a fitting on the hull, for that fitting to the primer ball, then to the motor. I inspected all the ones on the motor itself and they looked fine.

I don't remember the exact cost but it was around $50. I bought the new fuel lines, a clear inline plastic see through fuel filter I put right before the water fuel seperator and some new clamps.