Poor Running 225hp four strokes?

[wjob]

My son has got problems with two 225hp, 2003 Yamaha 4 strokes on the back of a 27' Wellcraft Coastal. They've got about 850 hrs on them. He's got a Racor in the bilge for each plus there's also a filter on each engine.

Sometime they run ok but then one will sart to miss and or not rev up and then eventually conk out, then the other one might act up, or one or both might run fine. He can usually re-start them by pumping up the priming bulb. This has been going on for some time and he's had various techs try to solve the mystery but none have. General feeling is that it's a fuel problem? Theyv'e replaced the fuel pumps (understand there are 2 on each engine), Most recently they replaced 3 of the fuel injectors based on a computer input and of course they constantly change/drain/nspect their fuel filters. Theyv'e also bought their fuel at diffferent locations in case that was the problem.

Will appreciate any thoughts

Bill

 

[wjob]

Re: Poor Running 225hp four strokes?

vfrkent replied:
"I would check the gas tank venting system, sounds like it may be plugged."

I mistakingly posted to the Johnson forum where Kent kindly replied, after which I switched it to this Yamaha forum.

The venting system checked out ok so we still are looking for answers/sugestions?

thanks
Bill

 

[jeffersondodson561]

Re: Poor Running 225hp four strokes?

did they check the fuel system for air leaks or unacceptable vaccum level? Fuel pumps which ones low or high?

 

[user64]

Re: Poor Running 225hp four strokes?

Crud in the fuel pickups or in the anti siphon valves?

 

[wjob]

Re: Poor Running 225hp four strokes?

They did check for air leaks and unacceptable vaccum...checked fine. Also checked the fuel pickups and the anti siphon valves for crud.

Question about the fuel pumps? Over the last 4 months theyv'e replaced all 4 pumps, both the low and high on each engine. Now the tech is saying the lower pump on each engine not responding to electrical input. Going to try and swap them out under warranty. Any suggestions/comments?

Bill

 

[SparkieBoat]

Re: Poor Running 225hp four strokes?

you can get the injectors cleaned for about $25 per. I would get them all done and flow tested. (changing out 3 injectors is kinda an odd thing to do) most places will give you a report of flow test before and after cleaning. many fuel issues with these motors. unfortunately they are quite difficult to trouble shoot. you need to test and set each sensor and the ISC valve. check 5v reference, ECU showing any codes?? I managed to get mine running good again, but I did a 3 month, on again, off again, lessons on Yamaha EFI system, there was a lot for me to learn. Even the Yamaha Master Techs have problems diagnosing these motors sometimes. I could tell you of some real horror stories. sounds like your tech may be costing you some real dollars, that may be just his guessing game. (those fuel pumps aint cheap and probably did not need replacing, I mean all 4?? that would be very unusual. the fuel pumps can be easily tested, with a fuel pressure gauge. The VST needs to be cleaned yearly and the screen/filter on bottom of high pressure fuel pump.) Good Luck.

 

[jeffersondodson561]

Re: Poor Running 225hp four strokes?

Now the tech is saying the lower pump on each engine not responding to electrical input. Going to try and swap them out under warranty. Any suggestions/comments?

The chances that both ECM's are coincidingly not putting out the right voltage to both motors is very unlikely. Do you have one tank or two? Meaning do both motors run off the same tank. A lot of times mechanics will just change the water seperator and not change the boat fuel filter(s), the fact that engine performance is improved when primer bulb is squeezed means a probable fuel issue. Have they changed all filters on the engine. Gas entering the engine is filterrd numerous times. If the mechanic suspects injectors make sure he does a fuel injector balance test using Yamaha software if they all drop in the same amount of time chances are fuel injectors are not the problem. Have they pulled the fuel pickup out of the tank?

 

[wjob]

Re: Poor Running 225hp four strokes?

Appreciate the replies. I believe he has one tank. I agree, if it were me, I wouldn't have been in a hurry to replace all 4 pumps. Theyv'e checked, drained and/or changed all fuel filters and water separators The one between the tank and the engines is a Racor. It's my understanding that the last tech to work on it said there was good fuel flow to the engine, not sure if he meant to the
lower fuel pump intake or through to the output side. I guess just to the input side, thus the reason he says they are bad again and need to be replaced.

One tech did do a computer check of the fuel injectors, not sure what software he was using, that's when three were condemed and replaced. Said the others were ok. They have pulled out and checked the fuel pickup.

Don't believe ECU is showing any codes. What's the 5v reference about?

thanks
Bill

 

[jeffersondodson561]

Re: Poor Running 225hp four strokes?

Five volt reference refers to the most of the sensors used on modern engines today, with the exception of O2 sensors and knock sensors. The ECU sends out a constant 5 volts to these sensors, the sensors react to what they are monitoring by adjusting the resistance (usally caused by temperature, pressure or motion) thus sending information back to the ECM. The resistance the sensor measures is subsequently received as voltage value, that value is inserted into a map stored in the ECM and calculated to try to acheive stoichiometric air fuel ratio (14.7:1). All at a 186,000 miles per second

To be more simple imagine I am the ECM and you are the temperature sensor with a thermometer in your hand and for every 10 degree change that you notice I want you to dim the lightswitch 10%, I see that (via wire) and plug it into my excel word sheet. Or you can be the ECM, I don't care.

 

[wjob]

Re: Poor Running 225hp four strokes?

Thanks Jeff.......very good and helpful. Should have more info on situation this coming week, will post when I do.

 

[SparkieBoat]

Re: Poor Running 225hp four strokes?

I want to be the ECM next!!!