Go Back  The Hull Truth - Boating and Fishing Forum > BOATING FORUMS > The Boating Forum
Reload this Page >

Yamaha F250 Losing Power and Backfiring

Notices
Like Tree8Likes

Yamaha F250 Losing Power and Backfiring

Old 04-02-2019, 07:04 PM
  #41  
Senior Member
 
Join Date: May 2015
Posts: 268
Default

i am baffled...but wondering if we are all missing something simple. I wonder if under the right conditions, your motor is grounding out?? maybe it has been so intermittent because the wire is not always shorting to ground? that would act like backfire / with power loss... (yes I am guessing at this point)
REGMARINE26FS is offline  
Old 04-03-2019, 12:54 AM
  #42  
Senior Member
 
Join Date: Aug 2017
Posts: 187
Default

REGMARIME26FS may be on to something, I had a similar situation when I replaced one of my coils - a few strands of wire were exposed and were arcing...
DaveHNL is offline  
Old 04-03-2019, 02:50 AM
  #43  
Senior Member
 
Join Date: Jul 2012
Posts: 245
Default

What is your fuel pressure?
brendanm is offline  
Old 04-03-2019, 03:57 AM
  #44  
Senior Member
 
Join Date: May 2015
Posts: 268
Default

Originally Posted by DaveHNL View Post
REGMARIME26FS may be on to something, I had a similar situation when I replaced one of my coils - a few strands of wire were exposed and were arcing...
and the ARC / Short to ground may only happen under certain temperatures / humidity / blah blah blah. This COULD explain why all fuel related possibilities are seemingly not the issue at this point. (but i would still like to know the fuel rail pressure)
REGMARINE26FS is offline  
Old 04-03-2019, 04:04 AM
  #45  
Senior Member
 
Join Date: Mar 2016
Location: Washington, NC
Posts: 1,075
Default

I had something similar happen to me while 40 miles off shore. It turned out to be the primer bulb, only it was not showing typical symptoms of being sucked compressed. But when removed and trying to blow though it was barely flowing anything. This all when boat was relatively new. Itís a cheap and easy thing to replace.
Stevesmarsh is offline  
Old 04-03-2019, 04:40 AM
  #46  
Senior Member
 
Join Date: Jan 2019
Posts: 866
Default

Ditch the anti siphon and clean gas tank. Sounded like vat or bad coils at first
Tossedabout is offline  
Old 04-09-2019, 07:19 PM
  #47  
Member
Thread Starter
 
Join Date: Sep 2018
Posts: 34
Default

Originally Posted by DaveHNL View Post
Maybe try swapping the injectors on the cylinders that are firing to the ones that aren't.
Good idea. We havenít tried that.
Capt_Paul is offline  
Old 04-09-2019, 07:29 PM
  #48  
Member
Thread Starter
 
Join Date: Sep 2018
Posts: 34
Default

Originally Posted by REGMARINE26FS View Post
i am baffled...but wondering if we are all missing something simple. I wonder if under the right conditions, your motor is grounding out?? maybe it has been so intermittent because the wire is not always shorting to ground? that would act like backfire / with power loss... (yes I am guessing at this point)
All we are doing is guessing too. This isnít intermittent anymore. The power loss is constant under load. On the muffs, it doesnít want to start, wonít idle, and backfires. In the water, we get the same results only it wonít run over 1500RPMs. After the fuel feed pump fuse blew, we thought it was possibly a bad ground. But when upgrading from 5 amps to 10 amps, it quit blowing. Guessing party in Ukiah? Iíll buy beer?
Capt_Paul is offline  
Old 04-09-2019, 07:32 PM
  #49  
Member
Thread Starter
 
Join Date: Sep 2018
Posts: 34
Default

Originally Posted by DaveHNL View Post
REGMARIME26FS may be on to something, I had a similar situation when I replaced one of my coils - a few strands of wire were exposed and were arcing...
These arenít traditional coils. The coil is at the end of the boot. Technically, no spark plug wires other than the connector to the coil.
Capt_Paul is offline  
Old 04-09-2019, 07:37 PM
  #50  
Member
Thread Starter
 
Join Date: Sep 2018
Posts: 34
Default

Originally Posted by brendanm View Post
What is your fuel pressure?
Three shops tested it and said it was good. I don’t have the Yamaha fitting needed to test it. The first shop said it was 44psi. The aren’t a Yamaha shop. The two Yamaha mechanics said it was good.


Capt_Paul is offline  
Old 04-09-2019, 07:49 PM
  #51  
Member
Thread Starter
 
Join Date: Sep 2018
Posts: 34
Default

Originally Posted by REGMARINE26FS View Post
and the ARC / Short to ground may only happen under certain temperatures / humidity / blah blah blah. This COULD explain why all fuel related possibilities are seemingly not the issue at this point. (but i would still like to know the fuel rail pressure)
Fuel pressure on the high side was 44psi.
Capt_Paul is offline  
Old 04-09-2019, 07:55 PM
  #52  
Member
Thread Starter
 
Join Date: Sep 2018
Posts: 34
Default

Originally Posted by Stevesmarsh View Post
I had something similar happen to me while 40 miles off shore. It turned out to be the primer bulb, only it was not showing typical symptoms of being sucked compressed. But when removed and trying to blow though it was barely flowing anything. This all when boat was relatively new. Itís a cheap and easy thing to replace.
The bulb was brand new when we mounted the motor in May 2018. Changed it twice last season thinking that was the problem. If you read the original post and following comments you will see that the fuel problem has been resolved. Now we seem to be running only 2-3 cylinders.
Capt_Paul is offline  
Old 04-09-2019, 08:04 PM
  #53  
Member
Thread Starter
 
Join Date: Sep 2018
Posts: 34
Default

Originally Posted by Tossedabout View Post
Ditch the anti siphon and clean gas tank. Sounded like vat or bad coils at first
This doesnít have anything to do with the current situation. The anti siphon valve was installed with the new fuel pickup when we were having fuel pressure problems. I took it out the next day. I canít even tell you how many times we took the VST apart and cleaned it. The last time was a few days before we had the latest issue. We took it apart and replaced the screen filter, horseshoe filter, gasket, and high pressure pump. We have tested the coils and believe they are good.
Capt_Paul is offline  
Old 04-09-2019, 08:11 PM
  #54  
Senior Member
 
Join Date: Jul 2012
Posts: 245
Default

Originally Posted by Capt_Paul View Post


Three shops tested it and said it was good. I donít have the Yamaha fitting needed to test it. The first shop said it was 44psi. The arenít a Yamaha shop. The two Yamaha mechanics said it was good.
It's good now, when its constantly playing up? Or it was good before when intermittent? You need to start with the basics while its constantly playing up. Your symptoms sound like low fuel flow.
brendanm is offline  
Old 04-10-2019, 08:22 AM
  #55  
Admirals Club Admiral's Club Member
 
Join Date: Mar 2006
Posts: 159
Default

Is it possible, that initially, you had a small exhaust leak due to corrosion, hence the intermittent issues and once the exhaust leak got bigger, itís caused the sysmptoms to manifest all the time?
Tangled Up likes this.
Blues Brother is offline  
Old 04-10-2019, 11:00 AM
  #56  
Admirals Club Admiral's Club Member
 
Join Date: Mar 2005
Posts: 706
Default

Sounds like exhaust corrosion in the cylinder head. Valve or valves may be stuck open. This type of leak will mix water in oil. When this happens the valves get messed up causing the cam timing to go out. You mentioned cam sensor errors correct? Pull the cylinder heads. I had the same problem. I have a cylinder head in my garage with a hole the size of a dime in the exhaust area of the cylinder head.
Tangled Up is online now  
Old 04-15-2019, 01:22 AM
  #57  
Member
Thread Starter
 
Join Date: Sep 2018
Posts: 34
Default

Originally Posted by Tangled Up View Post
Sounds like exhaust corrosion in the cylinder head. Valve or valves may be stuck open. This type of leak will mix water in oil. When this happens the valves get messed up causing the cam timing to go out. You mentioned cam sensor errors correct? Pull the cylinder heads. I had the same problem. I have a cylinder head in my garage with a hole the size of a dime in the exhaust area of the cylinder head.
One of the Yamaha shops checked the cam timing and apparently it was fine. When we did the water test, we did not get any water in the crankcase. No water came out of the oil drain.
Capt_Paul is offline  
Old 04-15-2019, 01:58 AM
  #58  
Member
Thread Starter
 
Join Date: Sep 2018
Posts: 34
Default

This week we pulled the power head to resolve the oil leak. The oil pump looked pretty bad and so we are replacing the whole thing instead of just seals. Everything else looked pretty good. Didn't look like we had any exhaust corrosion issues. As we were disconnecting everything we noticed that water had gotten inside the wiring harness connector. The hot lead was badly corroded. The female end actually broke off and stayed connected to the male pin. We think this was causing electrical issues that both caused the intermittent issues as well as the consistent power loss. Ordering parts and hoping that it fixes out issues. There was an electronic valve of some sort mounted to the rear part of the bottom cowling.We broke this removing the power head. My mechanic here thinks it was some sort of vacuum sensor, however, I cannot find the part in the part diagrams. It has a hose on one end and an electrical connector on the other. Anyone know what this is or can get me a part number? The pic with me holding the broken piece is the part we are trying to identify.


Capt_Paul is offline  
Old 04-15-2019, 03:57 AM
  #59  
Senior Member
 
Join Date: Jul 2011
Posts: 5,604
Default

that is the (optional) sensor for converting cooling water pressure to an electrical value,
for display by Command Link gauges / NMEA 2000.
The same sensor is alternatively used to convert pitot tube water pressure to speed.

That small metal hex is the original style,
which was notorious for allowing water to pass into the wiring harness,
causing havoc with the ECM reference voltage
and thus other essential operating sensor outputs.

The revised part has a much larger metal hex body.

Name:  speed-WP-sensor.png
Views: 263
Size:  430.9 KB
Fwpratt is offline  
Old 04-15-2019, 08:11 PM
  #60  
Senior Member
 
Join Date: May 2015
Posts: 268
Default

Originally Posted by Capt_Paul View Post
This week we pulled the power head to resolve the oil leak. The oil pump looked pretty bad and so we are replacing the whole thing instead of just seals. Everything else looked pretty good. Didn't look like we had any exhaust corrosion issues. As we were disconnecting everything we noticed that water had gotten inside the wiring harness connector. The hot lead was badly corroded. The female end actually broke off and stayed connected to the male pin. We think this was causing electrical issues that both caused the intermittent issues as well as the consistent power loss. Ordering parts and hoping that it fixes out issues. There was an electronic valve of some sort mounted to the rear part of the bottom cowling.We broke this removing the power head. My mechanic here thinks it was some sort of vacuum sensor, however, I cannot find the part in the part diagrams. It has a hose on one end and an electrical connector on the other. Anyone know what this is or can get me a part number? The pic with me holding the broken piece is the part we are trying to identify.


It sounded like a ground issue, or an electrical issue-----but i am not sure i could have found that one. Learn something new every day. Hopefully it will fix your problem
REGMARINE26FS is offline  

Thread Tools
Search this Thread