In Need of diagnostic Guidance

[klpaul]

I have a 90hp OMC quietrider and need some advice other than throw it away. It currently has 17 pitch prop, new coil packs, plugs and wires and been decarbed and cylinders cleaned. compression is 130,110,125,and 115. Maxes out at 4500 RPM's with light load. In addition the lower two plugs are always a little wet and the top two dry. The strangest part is after cleaning out the cylinders and running on the lake, it achieved 5200 RPM's for a short time. Could this be due to the extra combustible chemicals in the chamber, moisture on the rings. Where do I start? In addition, raising the engne I don't believe is an option on this lizard.

 

[ob]

Re: In Need of diagnostic Guidance

What boat is the 90 pushing with the 17" prop?Have the carburetors been verified clean with no restrictions in any fixed orifices or porting?Is the engines lower unit anti-ventilation plate roughly even with the boat pad when trimmed level?

 

[klpaul]

Re: In Need of diagnostic Guidance

It is pushing a 19 foot sunbird Eurosport. It appears that the anti ventilation- plate is below pad level. Can I simply just use a tape measure and level for this? I am almost positive however that this engine can not be raised as it has a very funky mounting arrangement that I have never seen. (I hope I am wrong)

I have not carbs the carbs but supposedly they were just rebuilt (I was given the repair receipt from seller but now I am suspect that maybe it was one of the two.

Any way carbs help diagnose the carbs other than inspection upon removal?

 

[tashasdaddy]

Re: In Need of diagnostic Guidance

what year is the motor or model # . they 110, 115 and wet plugs concerns me. look at the carbs if only one was done it should have a few wrench mark on on the nuts.

 

[R.Johnson]

Re: In Need of diagnostic Guidance

I would pull the head, and take a look at that low reading cylinder. If that cylinder show's damage, no amount of adjusting, or part's changing will help. Simply pulling the head can save a lot of time, and money.

 

[klpaul]

Re: In Need of diagnostic Guidance

Thank you so much for the replies. Tashadaddy, the model number is V90SLEIE. It is the 1991 infamous quiet rider. As far as wrench marks I can not tell. The wet plugs are on the two lower cylinders which are not the lowest compression cylinders (those two were 125 and 115). I was told however that to properly do a compression test I have to open to WOT. (I did not do this.) Is this true? If so it would explain why each one progressively decreased. (Please be patient with my ignorance) I am removing the carbs tomorrow to clean out the jets and look over. I advanced the timing tonight and was able to greatly increase RPM"s but I am very uneasy about this not knowing of potential damage I can cause. Should I be?

 

[clemsonfor]

Re: In Need of diagnostic Guidance

Compression test can be done with. Just with the starter turning the motor.

 

[rickdb1boat]

Re: In Need of diagnostic Guidance

Might try a decarb and see if you can get those compression numbers closer together:

Decarb Procedure:

http://www.iboats.com/bbboard/bbBoard.cgi?a=viewthread;fid=36;gtid=1035555

 

[R.Johnson]

Re: In Need of diagnostic Guidance

Until you know the condition of the cylinder's in that engine, why grope further? I can remove the cylinder head's much faster than the carb's. That could well tell me to stop right there. You can clean the carb's, decarb, etc., but again, you could be grooming a dead horse.To what point did you advance the timing?

 

[klpaul]

Re: In Need of diagnostic Guidance

OK. A small update. I discovered that the throttle lever sleeve for the advance timing arm was missing. The advance timing was thus severely lagging at WOT. Yesterday, I averaged about 5200 at WOT. I wiil Decarb with the above procedure this week and thank you. Plugs still have a lot of wetness that is black and gummy. (I hope the decarb you provided eliminates this or is it normal for a two stroke)

As for the compression and inspecting the cylinders. Second check results of 128 124 115, 124, 115 and 115. My question is will this be OK at least until the end of summer before inspecting the cylinders. If OK, I would rather wait because I may want to go ahead and renew piston rings if you advise.

 

[klpaul]

Re: In Need of diagnostic Guidance

Sorry for typo, long day. compression readings are 128, 124, 115, 115. Both 115's are on the port side.