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DT 225 Low power

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pgm181

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"I have twin dt225's. This

"I have twin dt225's. This week after sitting for 10 months I decided to try it out. Before going I serviced the engines with new fuel filters Low pressure and high pressure, also replaced all the spark plugs. I did add stable to the fuel awhile back. Here's what's happening, When I first left the dock after warm up, one engine runs great the other would not go above 2500 rpm and flucuated between 2000 and 2500 at wide open. So I cruised it 5 miles or so at 2000 and it began doing fine and did so all day 50 miles. Ok on the way in it ran fine until I had to slow for a wake area, once past the wake area I went to speed up again and the same thing happend as the morning, I replaced the high press. fuel pump on this engine 2 years ago for simalar symptoms hope its not that. Suzuki wants $450.00 for them. any ideas out there?"
 
Also I wanted to add that if I

Also I wanted to add that if I push the button on the throttles to release the drives the engine revs normally but the exaust smells a little strange.
 
"They are both 1998 models. Th

"They are both 1998 models. The engines are both supplied from the same tank of gas, one runs fine."
 
It sounds like there is a prob

It sounds like there is a problem in a sensor Maybe overheating probe or wiring maybe groken/corroded. This is a saftey feature of a lot of motors and is a random electronically induced miss to all cylinders. Its so that you can still get home without too much damage to the motor
 
"Ok it's getting interesti

"Ok it's getting interesting. Looking at the engine from the back facing the spark pluugs, the right lower cylinder has no compression. Dose anyone know what cyl.# this is? Anyway how can this engine run bad then good then bad again?? Can the reed valves cause this? I looked in the cyl. with a bore scope and all looks good. Piston and cyl. wall have no scares, also this engine never smoked or made any strange noises before now. I heard some strange ticking sounds when it was running bad, but went away when running good. Is there a possibility that there is carbon or some type of deposit intermitently holding the reed valve open? I have never de-carboned these engines. (1200 hours) I guess I should try that first?
Pat"
 
THE REED VALVES HAVE NOTHING T

THE REED VALVES HAVE NOTHING TO DO WITH CYLINDER COMPRESSION.That is the way it is.Reed valves have something to do with crankcase compression!!!Pull the cylinder heasd and inspect.This sounds like a teardown is in order.Remember when you have a plugged carburetor then no gas goes into one cylinder along with no oil to that cylinder. Remember too that a V-6 outboard is really 6 seperate engines with a common block and crankshaft.All cylinders function independant of the others as far as air/ spark / compression / and crankcase compression is concerned.
 
London Marine I dont know wher

London Marine I dont know where you get your info from as the crank case pressure is all to do with with cylinder comp-ression and the reed valve is all to do with crank case compression. You seem to be fixated with ripping heads off and pulling motors down before a thorough inspection. Also the oil is injected after carburation. Reed valves crack
Patrick I would also check the wiring to the temperature sensors. It sounds more like a broken wire that makes contact at times. Been there done that on a yammi after a supposidly top mechanic stripped the motor etc and after $1600 did not fix the problem.It was fixed by a drunk bush mechanic.
Is this motor carbies or fuel injection?
 
The engines are computerized f

The engines are computerized fuel injection. And oil injected. In the service manual (Suzuki) there is a set of reed valves per cyl. I suspect one reed valve hanging open or broken on the bad cyl. Still does not exlplain the running good then bad then good issue? Can a reed valve become severly gummed with deposits? And hanging open? Also how would a temp sensor cause no compression?
 
"Bob, after 40 years of workin

"Bob, after 40 years of working on these things you learn that the reed valves have to do with compressing the air in the crankcase.It is then "transferred to the cylinder" when this is done the exhaust ports and the intake ports are wide open thus no pressure is involved! Compression in the cylinder starts after the exhaust ports close.Don't believe this then take the reeds off a motor and do a " cylinder compression test " to see for yourself!"
 
It may be a combination of sev

It may be a combination of several things. You may even have a Friday/Monday motor. I would certainly take off that manifold and look at the reed valve.
A faulty temp sensor/wiring will alert the computer to a problem and then the motor is limited to 2500 revs.There is no way roud the computer unless the fault is fixed.
Check the reed valve first
 
Boat = bring out another $1000

Boat = bring out another $1000
Its a hole in the ocean to pour your money into.

london you beat me by many years. Im a bush mechanic by trade. I still dont rip off heads for the hell of it.
I took my yammi to an expert tradesman who bragged he could fix anything motor wise. Never again
 
"Bob, one of my last " wor

"Bob, one of my last " world class " inspections / trouble shooting episodes found an 84 -140 OMC with bad compression on 2 cylinders.The owner had someone look at it and said compression was OK had nice new plugs and wires too.Time taken to determine the trouble ---- less than 10 minutes.This party drove 3 hrs to see me because " reputation talks ".Motor has 4 new pistons installed and will run like new this spring!"
 
So I guess what you are saying

So I guess what you are saying is that the reed vales have nothing to do with compression?
Pat
 
Patrick will supply a final an

Patrick will supply a final answer I am sure!!
 
"Patrick, pull the cylinder he

"Patrick, pull the cylinder head as suggested earlier.You may be lucky and have a blown head gasket!Heck you could fix it yourself."
 
"If there were a blown head ga

"If there were a blown head gasket, that still doesn't explain the run good run bad issue? If a reed valve were to be bad, would it not allow air to enter into the crank case, there for not allowing anything to compress, ie no compression? Also is there a possibility that the rings are stuck in pistons due to deposits? Should I try adding some oil to the cyl. in question and testing again? Or perhaps decarboning with seafoam?"
 
"One more time----The 2 stroke

"One more time----The 2 stroke engine is magic ----So when the exhaust ports close compression in the cylinder starts and the pressure in the crankcase drops , the reeds open to let fresh air and fuel into the crankcase. SO DURING COMPRESSION THE REEDS ARE OPEN ---the reeds are not part of the combustion process.-----The reeds are nowhere near the combustion chamber!"
 
"LM- I now understand the 2 st

"LM- I now understand the 2 stroke cycle and agree with you. There is no way the reed valves can affect compression. I believe I will remove the cyl. head and take a look. I still find it curious why it ran bad then good then bad again? Perhaps when then engine warmed the head gasket sealed during heat expansion? Or the cyl. was misfiring all along, and I never noticed it until I had this new problem of what ever it is causing the B-G-B running condition. So fixing the cyl. problem I may still have another?"
 
"I have been dealing / trying

"I have been dealing / trying to teach people for many years.Some people learn quick and other just do not want to learn.I can be a good teacher if I have a good student.When I was 20 years old an individual said " if you ever open up your own shop let me know, will be your first customer ". Now i find people doubting my expertise, That is the way people are today I guess -- no respect.------------ Now get yourself an inductive pick-up timing light ( to use as a poor mans scope, not to check timing )Lay it / tape it in place so that you can observe the flash. Hook it up to the cylinder one and run the boat to full throttle and observe the flash.Repeat with the other 5 cylinders.If you have steady flash on all cylinders you do not have an ignition problem.Fuel injection on Suzuki motors I know nothing about so can not help there other than switching parts from one motor to the other."
 
I also wanted to note that I a

I also wanted to note that I am an A.S.E. master auto tech. with 35 years experience. Still working and have all the tools and equipment. Also the boat is stored at my shop. But 2 stroke engines and what I work on are quite different as you all know. The electronics aren't but the intake exaust process certainly is.
Pat
 
"I used a snap/on comp. gauge

"I used a snap/on comp. gauge on this engine. The cyl. in question read 0 comp. I tried one cyl. above it to test the gauge and had 150. I also have my own lab scope and specialize in drivability problems including fuel inj. and computerized engine controlls, but with no comp. I don't believe any of that experience is where I am at this point. Blown head gasket sounds more like what's happening here.
Pat"
 
"I also wanted to thank everyo

"I also wanted to thank everyone for all the interest and suggestions. I sure learned a lot this past few days. This is a great site. I just wish I new more about 2 stroke engines or outboards in general, so I could return the help to others in need. Thanks again to all. I will post again after I remove the cyl. head."
 
"Just wanted to let everyone k

"Just wanted to let everyone know. I have a burned piston. I have to replace a piston and have the cyl. sleeve replaced. I can do this repair myself, and am just waiting now for the machine shop to finish the cylinder. This is a in depth repair. I don't reccomend for just anyone to try. There are a lot of tools required as well as some experience. As I mentioned above I am not a marine tech. but have 35 years experience as an auto tech. with a lot of resources and tools/equipment."
 
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