loss of rpm - Another question for Dhadley

[codkiller]

Hello,<br /><br />This is a first time post on this forum. I have a 1990 200hp Evinrude pushing a 22ft Grady-White Seafarer. The powerhead has just been completely rebuilt as well as a new stator, new power pack, new timer base, new vro and carbs rebuilt. The 10hr brake-in is done with approx 12hrs on the motor. My problem is at WOT I can only get approximately 5000 rpm. The motor runs great with plenty of power. The timing has been checked and is right on, compression is 90 psi on all cylinders, and is definitely firing on all six. When this motor was new I consistently got 5500 rpm's which slowly declined to 5100 over the years due to low compression. What else could I check to get the 500 rpm's back? Or is 5000 rpm's all I can expect from this rebuild?<br /><br />Thanks<br /><br />Codkiller

 

[Dhadley]

Re: loss of rpm - Another question for Dhadley

Welcome!!<br /><br />What did the rebuilder say about the rpm loss?

 

[codkiller]

Re: loss of rpm - Another question for Dhadley

Dhadley thanks for the welcome. Unfortunately the rebuilder is being very difficult. They seem to have done a good job on the power head rebuild but neglected to do some of the extra work on the outboard which I paid money for. As a result I don't think I can count on any support<br />from these people.<br /><br />Thanks<br /><br />Codkiller

 

[Dhadley]

Re: loss of rpm - Another question for Dhadley

Thats a shame.<br /><br />Since they changed most everything in the ignition system I'm guessing they really didn't know what caused the original failure. <br /><br />Lets do some basic looking. What spark plugs did they put in?

 

[codkiller]

Re: loss of rpm - Another question for Dhadley

QL77JC4 gaped at .040<br />As far as the original failure I believe it was related to an over-heat condition which caused scoring in the cylinders.

 

[Dhadley]

Re: loss of rpm - Another question for Dhadley

OK, good info. Thats the right plugs which is good. <br /><br />Did they lower the motor by any chance?<br /><br />Lets look at the linkage. Without the motor running, put it in gear (you may have to spin the prop a bit) and wide open. Looking down at the throttle linkage on the carbs there is a mark (line) where the crossover linkage is. That should be straight forward and back.

 

[codkiller]

Re: loss of rpm - Another question for Dhadley

When you say lowered the motor are you talking about its location on the transome? If so the location has not changed since the boat was new.<br />As far as the linkage, I did check it and I am getting full throttle, the mark is straight front to back and the butterfly's are open full.

 

[Dhadley]

Re: loss of rpm - Another question for Dhadley

Does the motor feel sluggish at all?<br /><br />Do you know what they set the timing at? Its supposed to be at 18 but if they retarded it, that may be whats hurting the power.

 

[codkiller]

Re: loss of rpm - Another question for Dhadley

The motor does not seem sluggish at all, actually thats the first thing I noticed when running this rebuild for the first time, the respone from the throttle is remarkable, like I said plenty of power. I set the timing per many of the posts I read on this forum, manual spec less 4 degrees so I set the timing at 14.<br /><br />This is what I read on the reason for decreasing the full advanced timing by 4 degrees.<br /><br />"The reasoning for the 4° difference is that when the engine is actually running, due to the nature of the solid state ignition componets, the engine gains the extra 4°"<br /><br />"If you set the engine to its true setting at cranking speed, when running it will advance beyond its limit by 4° which will set up pre-ignition causing guaranteed piston damage! You don't want that to take place"

 

[Dhadley]

Re: loss of rpm - Another question for Dhadley

Thats true. Thats how we do it but we also check it aferwards, in the water under a load, to verify.<br /><br />Well, lets think about what else to look at. <br /><br />Is it the same prop? Not reconditioned or replaced?<br /><br />Gotta run some errands. Maybe someone else will have an idea.<br /><br />Does it seem to idle OK?

 

[codkiller]

Re: loss of rpm - Another question for Dhadley

Same prop no changes there. Idles fine 900 rpm

 

[Dhadley]

Re: loss of rpm - Another question for Dhadley

When you looked at the carb butterflies, did you have the airbox cover off? If not, pop it off and make sure the bottom one on each side is going wide open.<br /><br />BTW -- Im sure you already know this -- Never run the motor under a load with the box off. It'll lean out a piston.<br /><br />The only thing I can think of that will cost 500 rpm is if we are losing a cylinder (spark) at some point. We may need to run the motor and check each one with a timing light.

 

[james roach]

Re: loss of rpm - Another question for Dhadley

Are you sure you are not dropping a coil once underway? It probably fires fine when idling and drops out once you power up. Dont rule this out. 500 RPM sounds like 1 cylinder.

 

[codkiller]

Re: loss of rpm - Another question for Dhadley

Dhadley, Yes I did inspect the butterfly's with the airbox cover off, all were fully open. I have only run the motor with the air box off at idle speed. Unfortunately the only way I can check the spark at full throttle is on the water<br />which may be difficult with the boat going 40 mph, I suppose I could start and stop between cylinders.<br /><br />james roach, That is definitely a possibility. All I know is I can get to 5000 maybe 5100 rpm <br />fairly quickly and smoothly, just cannot get over that. Are you both in agreement that I should be getting 5500 rpm?

 

[codkiller]

Re: loss of rpm - Another question for Dhadley

Dhadley, Failed to mention I did test with a timing light running at idle mamy times didn't miss a beat on all six, this is not to say I could be droping a cyl at WOT. I do think at WOT the motor sounds and runs to good to be dropping a cyl.

 

[Dhadley]

Re: loss of rpm - Another question for Dhadley

Actually no. You should be closer to 6000 but you should certianly be getting everything you had before, and perhaps a tad more -- not less.<br /><br />I really think you need to let the builder know, just in case. But I think we all agree its probably losing spark on one cylinder at some point. Who knows? Perhaps one of the new ignition components is bad. It happens. If the dealer installed the components, it should be under the manufacturers warranty.<br /><br />Whose components did he use?

 

[codkiller]

Re: loss of rpm - Another question for Dhadley

Rapair CDI, the power pack and the stator were replaced by them I replaced the timer base.

 

[codkiller]

Re: loss of rpm - Another question for Dhadley

Dhadley, Do you think that after all this time I could be running the wrong prop on this boat? I don't know the size off hand, I'm in the office, I will post the size when I get home tonight.

 

[Dhadley]

Re: loss of rpm - Another question for Dhadley

I'm not too worried about it being the wrong prop -- perhaps the set up could be a bit "tweaked" to produce some more efficiency. Once we get back to square one (5500) we can play with that. <br /><br />Actually its good that he used CDI units. Great guys. If the installing dealer will not help, which after all that money -- he should, you can call CDI. They are very helpful.

 

[codkiller]

Re: loss of rpm - Another question for Dhadley

Been there done that, and yes the guys at CDI are great especially TJ and Ray. Forget about the rebuilder, there is a long history in regards to what I went through with this rebuilder, way to much info for this forum. I would love to chat with on the phone, is there an email address I can reach you at.