View Full Version : Is it possible?
tmdog
09-10-2006, 11:07 AM
Eight months ago I replaced my blown outdrive with a generic (Sterndrive Eng.) outdrive. I have lost 700 rpm at wot. Is it possible the gears or whatever is causing this recent loss? I checked everthing mechanical that would possibly result in the missing rpm. Things checked as follows: compression, carb rebuilt, plugs, fuel pressure at wot, and timing. The 18C would pull a 23 prop to 5300 and now labors at about 4200 to 4600 and the gps speeds dropped at these lower rpm's compared when it ran strong. I did notice a strange shuttering when planing off and a vibration all through the rpm range. Also shutters coming off plane. Prop is new. OD still under 1 yr. warranty. Tried different prop, same results. Is the OD suspect? Jim
gcarter
09-10-2006, 11:13 AM
Mine was down about 200-300 RPM and whined when new.
Now after about 25 hours, It may be down 100 RPM, but I'm not sure as that amount might be due to nothing more than temp and humidity. Also the whine is gone.
P.S.;
I'm running Amsoil synthetic gear oil.
tmdog
09-10-2006, 12:44 PM
I had the whine also. Checking my notes, I had called Sterndrive Tech on Nov 05 to report a vibration and whine. Tech told me whine would disappear and call them if vibration doesn't subside. Had 6 hrs. on drive than. Fact is, can something in the drive lose that many rpm?
gcarter
09-10-2006, 12:50 PM
Gear faces that aren't polished, bearing tolerances just a tad on the tight side.......
You see some assemblies that, due to the luck of the draw, might just have a tighter tolerance stackup. Generally just more use will solve these things.
Oh yeah, I also ditched the drive pump.....so that drag isn't there.
tmdog
09-10-2006, 03:00 PM
With 45 hrs. on drive, I would think the gears have meshed to their final stage. The shuttering getting up and off plane worries me. The feeling is like the prop has hit bottom, yet I am in 40 ft. of water. Losing all that rpm worries me the most.
Using Merc. oil in drive, changed once. First at 9 hrs.
mrfixxall
09-10-2006, 03:00 PM
Eight months ago I replaced my blown outdrive with a generic (Sterndrive Eng.) outdrive. I have lost 700 rpm at wot. Is it possible the gears or whatever is causing this recent loss? I checked everthing mechanical that would possibly result in the missing rpm. Things checked as follows: compression, carb rebuilt, plugs, fuel pressure at wot, and timing. The 18C would pull a 23 prop to 5300 and now labors at about 4200 to 4600 and the gps speeds dropped at these lower rpm's compared when it ran strong. I did notice a strange shuttering when planing off and a vibration all through the rpm range. Also shutters coming off plane. Prop is new. OD still under 1 yr. warranty. Tried different prop, same results. Is the OD suspect? Jim
did you check your drive aleignment? ck aleignment,rotate motor 90 degrees ck aleignment,rotate motor another 90 degrees ect ect..to see if your coupler is out of round...
tmdog
09-10-2006, 03:07 PM
New coupler. Spent many hrs. getting to line up drive. Good point. Got me thinking.
gcarter
09-10-2006, 03:19 PM
Do you have a drive shower?
For $50-$125.00, it might be worthwhile.
I suppose it might be possible from getting hot @WOT w/o one.
mrfixxall
09-10-2006, 03:33 PM
New coupler. Spent many hrs. getting to line up drive. Good point. Got me thinking.
check the lower nuts on the motor mounts,they may have come loose.....
also make sure the tab is bent ovet the nut to keep then from loosening up..
mrfixxall
09-10-2006, 03:56 PM
engine shudder check your firing order,i think cylinders # 5 & 6 or 5& 7 are crossed will still idle and still run but will be down on power...
FOSTER
09-10-2006, 06:26 PM
Are you still using same kind of gas? changed to etohonal ? Or lower octain.
Did the RPM loss happen when you installed the new drive? If so I would bet you any amount of money that the drive ratio is different in the new drive.
I would pull it off and check it. I can tell you how, if you do not know how to do it.
Did the RPM loss happen when you installed the new drive? If so I would bet you any amount of money that the drive ratio is different in the new drive.
I would pull it off and check it. I can tell you how, if you do not know how to do it.
I think you are probably spot on. 700 rpm is a lot to lose due to break in friction.
tmdog
09-11-2006, 11:58 AM
Do you have a drive shower?
For $50-$125.00, it might be worthwhile.
I suppose it might be possible from getting hot @WOT w/o one.
Installed after coming home from AOTH at Cumberland. It did warm up some at that event and chaulked the top cover.
tmdog
09-11-2006, 12:09 PM
Did the RPM loss happen when you installed the new drive? If so I would bet you any amount of money that the drive ratio is different in the new drive.
I would pull it off and check it. I can tell you how, if you do not know how to do it.
MrX and Cuda, GPs speeds are the same at the low and medium rpm's. So gearing should not be the problem. Pulls good to about 4k and gets really sluggish to 4600. I am really scratching my head over this and have not figured it out as of yet. If it keeps shuttering and vibrating, something bad is going to happen. I hope I can find the problem and a solution soon to avoid this happening.
With a wrong ratio, the speeds would still be close at low and mid RPMS
Pull the drive and check the ratio.
BigGrizzly
09-11-2006, 07:39 PM
I agree with ted. what scares me id the shuttering just male sure it isn't detonation. The otherthing could if you have a MSD box it could gone south
MrX and Cuda, GPs speeds are the same at the low and medium rpm's. So gearing should not be the problem. Pulls good to about 4k and gets really sluggish to 4600. I am really scratching my head over this and have not figured it out as of yet. If it keeps shuttering and vibrating, something bad is going to happen. I hope I can find the problem and a solution soon to avoid this happening.
Are you pulling the same speed at 4600 as you did at 5300, or the same speed at 4600 with both drives?
tmdog
09-12-2006, 02:30 PM
I agree with ted. what scares me id the shuttering just male sure it isn't detonation. The otherthing could if you have a MSD box it could gone south
No MSD. Running a Davis Unified Ignition (DUI). Total timing is set at 32* at 3200. Somewhat conservative, I'd say. DUI was installed same time as OD. Does the timing sound correct at that rpm? If not ignition can be recurved.
tmdog
09-12-2006, 02:39 PM
Are you pulling the same speed at 4600 as you did at 5300, or the same speed at 4600 with both drives?
For the first question, heck No. I only recorded speeds to 4000 and they are the same as before. Presently 61 gps at 4600 and it struggles badly. After 4k seems like everything gets tight. Was into the low 70's at 5300 with old drive.
BigGrizzly
09-12-2006, 03:06 PM
Timing could cause this. On my setups I run low advance bexause of the combination I use. However my car (71 mach I) with the same engine as the Corsican runs 37' at full advance. What wads the timming with the old system. It seems it all started at the same time. New OD and new ignition system. Maybe there is a spark plug issue too.
mrfixxall
09-12-2006, 03:07 PM
tmdog,when you added all the steel braided stuff did you install braided wires too?
mrfixxall
09-12-2006, 03:31 PM
No MSD. Running a Davis Unified Ignition (DUI). Total timing is set at 32* at 3200. Somewhat conservative, I'd say. DUI was installed same time as OD. Does the timing sound correct at that rpm? If not ignition can be recurved.
ooooo you have that set up,,pull cap to see if the carbon in the center of the cap is still their...that dist needs a good ground rite to the coil...make sure the grounding tab under the coil is not coroaded...if not grounded properly it will melt the cap and or the coil..
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