Engine Timing/ WOT RPM's

[FreeBeeTony]

If an egine's timing is too far advanced will this gave any affect on the WOT RPM's? I recentky rebuilt an older Mercruiser 165 IL6. I had a hard time finding the timing mark on the vibration damper and the readings on the timing flange on the block are not visible. Assuming the middlie of the timing flange is 0 degrees, I set the timing mark to about 1/2 inch advanced. Mid way between the middle of the timing flange and the end. The engine is only turning 3500 RPM's at WOT and its running hot (>180). The boat is a 20' Grady White Gulfstream with a 17" pitch prop.

 

[galaxy]

Re: Engine Timing/ WOT RPM's

assuming your timing flange is the original one, zero should be a little bit to the right on the flange. There should be a deeper indention between the teeth points at zero. If you were able to see the marks, they would be in 2 degree increments. So from one tooth point to another would be a total of 4 degrees. However, yours may be a little different than mine. I have a 77' 165 all original. Also the sticker on my engine says timing to be set at 6 degrees BTDC. I've been reading where several folks say 8 degrees but I'll go with the manufacturer.

 

[galaxy]

Re: Engine Timing/ WOT RPM's

Also Tony, It sounds like you may have advanced your timing too much. Providing you can locate zero, you should set it to the left, which is "before" zero. Also I may have told you wrong about the degrees between two tooth points. On mine, if you started at zero and went left, you would have 4 degrees to the first tooth point and we'll call it the "valley" between that tooth point and the next would be another two degrees which would give you 6 degrees BTDC. I hope I'm not confusing you on this. Maybe someone else could explain it better than me.

 

[FreeBeeTony]

Re: Engine Timing/ WOT RPM's

The engine I rebuilt is stamped 1967, what's left of the timing marks appears to be towards the port side of the engine on the side of the timing cover. I just looked at another block I vahe and the timing marks are at 12:00 on top of the timing cover between the vibration damper and the water pump pulley. Did GM change something or am I setting the timing to the wrong spot? If I am at the wrong spot, I would be about 30 deg retarded. Is this possibe and still run?<br />Galaxy, where is the timing mark on your block?

 

[galaxy]

Re: Engine Timing/ WOT RPM's

If your referring to the harmonic balancer, There should be a groove cut into the outer surface of the balancer. You should get some white paint or chaulk to highlite the mark with. I use a small bottle of tub and tile touch-up paint. Since your engine is a 67' model I'm not sure what your timing would set too. I'll try and find out and get back to you. How many tooth points on your tab and are they spaced equally apart from one side to the other?

 

[FreeBeeTony]

Re: Engine Timing/ WOT RPM's

The teeth on the tab are not visible. I reset the timing more towards retarded but still BTD (I think). Seemed to run cooler but still can't get WOT RPM's.

 

[galaxy]

Re: Engine Timing/ WOT RPM's

Do you have a re-built truck engine or marine mercruiser?

 

[FreeBeeTony]

Re: Engine Timing/ WOT RPM's

GOOD QUESTION! The one in the boat is a marine mercruiser, the one I was comparing it to was a GM block. I didn't think of that before, good pick-up! Anyway, I retarded the timing somewhat and it seems to run cooler] but still can't get the wot rpm's. Any other ideas?

 

[daveswaves]

Re: Engine Timing/ WOT RPM's

Hi Tony, I think I mentioned in one of my posts before, but you may have to drop down to a 15 pitch prop. I run the same engine, similar boat, 15 pitch is the most I can run. Anything higher and the rpm drops cause the engine is working too hard. Temp will go up as well.

 

[FreeBeeTony]

Re: Engine Timing/ WOT RPM's

Dave, what type of boat are you running? You have an IL6 GM 250 cui? What is your WOT RPM's with the 15" prop? What outdrive ratio do you have?

 

[galaxy]

Re: Engine Timing/ WOT RPM's

Dave has a good point. That could be your answer right there! I'm running a 15x19p.

 

[galaxy]

Re: Engine Timing/ WOT RPM's

Tony, from what I've read about props, higher pitch = higher speed. Lower pitch = higher rpm's.<br />does your boat have a speedometer? Compare your mph to your rpm's. I'm going to the lake this week and I'll check what mine is running. By the way my prop is 15x19p. I was thinking it was a 15p.

 

[Spidybot]

Re: Engine Timing/ WOT RPM's

As the engine setup and tuning has to be correct no matter what prop you use, getting first things right is way to go. Once you know that it is running right you can concantrate on the prop issue.<br /><br />Getting proper rpm at wot by running a low pitch prop on a badly timed ignition is not the right way to go. Will even give you running problems and bad mileage.

 

[FreeBeeTony]

Re: Engine Timing/ WOT RPM's

Is there another way of determining if the timing is set properly? The WOT RPM's are currently abot 3300. I really haven't gotten on it yet though, the engine is still pretty fresh, only has about 4hrs on it.

 

[rabidfish]

Re: Engine Timing/ WOT RPM's

Tony... UU is on the right track here... First make sure the engine is running properly. Start with dwell. Then set timing. ( use an indicator to get piston # 1 at TDC. Then make a mark on the balancer with a paint stick at 0 degrees. Use an advance timing light to make your mark align with "0". Then take a reading form your timing light to check the advance. OK now for WOT RPMS.<br />If you haven't "gotten on it" then you do not have a WOT rpm reading. ( hence the term "WOT" )<br />Many things can affect the rpms. Prop certainly, but also trim angle. Also verify that you have the proper gear ratio in the drive. Many older boats have had replacement upper gear housing w/ incorrect gears. Before you get too involved... CHECK THE TACH ! most boat tachs have a selector on the back for # of cylinders. be sure to check the setting on the back of the tach. Also check it against another tach just for good measure. Good Luck!

 

[galaxy]

Re: Engine Timing/ WOT RPM's

Tony. Did you yourself rebuild this engine, and if not, Do you know the person who did? Also , How does the motor idle? Does it throttle up slowly without hesitation or misfire? We're all just making suggestions of possibilty's here, so maybe a little indepth information might be more helpful. The timing could be off but it sounds like, if it is, it's not off by much.

 

[hoot]

Re: Engine Timing/ WOT RPM's

i run a 17-1/2' boat, w/165. my WOT is about 4200 with a 21p prop. had lost ~800-1000 rpm. checked timing , point gap, wires, carb, finally replaced ig coil. seems to have solved problem. rpms back where they are supposed to be.

 

[galaxy]

Re: Engine Timing/ WOT RPM's

One move up or down in pitch can make a difference of 300-500 rpm's