Yamaha 250 four stroke issue

[got-tu]

I have a 2006 28' Sailfish with 250 Yamahas. 200 hrs total on engines. Today port engine stopped. No oil pressure. Since its Saturday mechanic did a quick check. No compression on all 3 cylinders of the left side, right is fine. Oil looks good & filled. Is there any other possibilities other than power head is blown. He mention timing gear failure as a possibility. He will dig into it Tuesday, but was hoping to sleep better before then if chance not blown.
Thanks
Got-tu

 

[GW 255]

Could you provide a little more information on the engines such as 2 stroke or 4 stroke any other issues you may have had with them. hard to give you an honest opinion without all the facts. sorry for your engine troubles...we have all been down this road before.

 

[GW 255]

IF it is a four stroke the first thing you would have to check is pull the plugs and take a peak in the cylinders to see if there is any discoloration of the cylinder walls and if the honing is still visible. when you say that the three cylinders had no compression do you mean zero or that is was just low, as that will make a difference in which way to go. since its a dual overhead cam design for that engine i would imagine that if your timing belt did in fact fail you should still see compression on at least one of the cylinders as not all of the valves will be in the same position at the same time. i would check your engine oil for water as this could be a sign that the head gasket for that bank failed. did you get any alarms before the engine failed?

 

[got-tu]

They are four stroke. Bought boat last Oct. Only have burned 60 gallons of fuel since then. Bought boat from a reputable dealer. No signs of problems before today. Ran boat 4 hours yesterday. All good. Mechanic did not find anything wrong with cylinders. No water in oil.

 

[got-tu]

Also No alarms. Engine RPM's slowed so cut engine off. Only tried to restart once. Saw the zero oil pressure didn't want to do further damage.
Thanks for your help and observations.

 

[GW 255]

assuming that the mechanic was able to roll the engine over freely to take the compression #'s that is a good sign which means the power head should be repairable. from what you have said the oil pump seems to have failed but the only way to know this for sure is to check the pressure using another gauge. as long as there is no other damage to the camshafts or crankshaft bearings you should be able to just replace the rings for those cylinders and re hone the liners if necessary. so when you say the engine dropped rpm did it bring the engine to a safe mode or was it like someone had killed the fuel to it and the engine was just stalling?

 

[got-tu]

Stalling

 

[GW 255]

ok then IMHO the problem most likely with the engine is that due to the failure of the oil pump the cylinders on the port side of the engine have overheated to the point of damaging the piston rings and will need to be re honed and new rings installed. you will also have to figure out why the oil pump failed because with that low amount of time on the engine it concerns me that the pump would have failed so quickly when most of those engines are easily going well past a 1000 hrs without major issue. I would recommend that oil ports in the block are flushed and the sump cleaned to make sure that there is no blockage that burned up the oil pump. otherwise a good mechanic can have this engine back up and running in no time as long as there is no other damage. good luck with the engine problems, let me know how you make out with it.

 

[got-tu]

Will post what mechanic says..
Also the hot alarm did not sound & the temp meter was showing in the middle when the motor quit.

 

[GW 255]

if the temperature was ok and the high temp alarm didnt sound that is a good sign which should mean the engine did not get too hot and you caught it fast enough.

 

[got-tu]

But I don't have compression on the 3 left cylinders. That can't be good

 

[GW 255]

yes but that can be due to ring failure for the pistons on that side due to the oil pump failing. like i said before as long as none of the bearings were damaged for crankshaft, camshafts, connecting rods, etc then youll be fine. you said the oil looked ok so if there wasnt any metal particulate in the oil then the bearings hopefully were ok. the film that was most likely on the bearings protected them long enough to shut down with no issue. until the heads are pulled and the cylinders checked for discoloration or scoring you will not know for sure. assuming the walls are scored in all of the cylinders you would still be able to have them machined, re honed and oversized rings installed for much cheaper than a new power head if the mechanic is reasonable pricewise.

 

[ric2352]

I don't see how you could lose compression on one bank ( are we talking "0" here??) without the rest being affected, especially in the event of oil pressure failure. I thinking valve train issues like timing belt slippage....which bank was affected? Sorry....I see left bank...not sure what you mean by that...how does your left bank relate to crank rotation?

 

[GW 255]

the odds of the camshaft failing in such a position that you would read 0 psi on any cylinders for that bank due to the valves being partially open is very little because of the firing order of a V6 engine. if any oil passages were blocked to that side of the block it would be very easy to damage the piston rings and cylinder walls to the point compression is lost. also if the engine wasn't broken in properly to start with the rings may have never seated properly for that engine. for the record the yamaha 250 is an interference engine which means if the timing belt did break you would most likely see valves impacting pistons and a great deal of noise when it occurs.

 

[wspitler]

Some of these symptoms are very unusual when taken together, don't make sense to me. Rings usually aren't the first thing to go with oil pump failure and only on one bank?? Timing belt would not only affect one bank? Stalling? I'd recheck compression and pull the plugs. A gas engine still runs with low compression, just no power.

 

[got-tu]

Thanks for all the replies. Mechanic which I have used for 15years, just did a quick look on Saturday. He will tear down the engine tomorrow. Will post what we find out.

 

[Sea Shift]

You have my attention for sure. I will be interested to see what he says.

 

[ROBERTH]

got-tu, where are you located? Sounds like a big fix here so far. Keep us posted!

 

[got-tu]

I live in Greensboro. Boat is in Wrightsville Beach. Mechanic hasn't given me the verdict yet. But I am expecting the worst. New power head.

 

[ROBERTH]

Ok, so fairly local and not from northeast where I had read some had more corrosion up that way than down here.

Hopefully the mechanic can figure out the cause of the failure.