# Loading motor for timing adjustments



## onthewater102 (Sep 22, 2016)

Short of the rickety way I did it (one person driving for me while I hang on the motor & try to check things while under way) how do normal people check and adjust timing on small outboards?

I read true test tanks require a test prop to load the motor without moving much water, but as I do not have such a device and they appear to be rather expensive I don't see that as much of an option.

Is strapping the boat down tight to the trailer and running the motor on the boat launch safe (provided no debris is around to entangle the motor etc.) so that the motor has a sufficient load on it?


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## DaleH (Sep 22, 2016)

onthewater102 said:


> Short of the rickety way I did it (one person driving for me while I hang on the motor & try to check things while under way) how do normal people check and adjust timing on small outboards?


I've done that ... with a 250hp OB no less. Worked! ... just don't tell the fiance :lol: My advantage was that I had a full transom boat with full-width swim platform, so it wasn't like I was hanging out there for dear life.



> Is strapping the boat down tight to the trailer and running the motor on the boat launch safe (provided no debris is around to entangle the motor etc.) so that the motor has a sufficient load on it?


Safe? Not sure, but I've done it ... but I may have a leg up, so to speak, as I'm on a tidal river and will do it so the prop thrust faces down-river at the time of maximum tidal flow. We also trimmed up the motor some. A local OMC dealer did check a 225hp my brother had using this same process, but tied to a heavy work dock. That also worked well.

I was doing the ol'_ sync & lync_ and could not locate a test prop to beg or borrow. I got quite friendly with neighboring Dealers and was able to borrow test props - in some cases - as I've sent them so much work over the years. I just do my own motors or those for my brothers, as at one time we had over a dozen for many years and then another dozen+ I had maintained for my boatclub.


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## onthewater102 (Sep 22, 2016)

Yeah..."Safe" is always relative to how well everything is secured, but I meant does it load the engine properly. Tying the boat to a sturdy dock seems less sturdy then heavy tie-down straps on the trailer. I've got a motor I'm trying to rebuild for a flip project but I'm pretty sure I caught my son out of the corner of my eye playing with the adjustable rod for the timing advance when I had it apart and before I get to the point of adjusting it to know its right I was hoping to come up with a better way than I did on my 1436...either that or hurry up and get it put back together while the water in CT is still warm enough that if I fall over it's all good


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## wmk0002 (Sep 22, 2016)

I prefer hanging off the back. I go in the morning when the water is glass and there isn't much boat traffic. It's also lower light so easier to see the timing light. Just stop for adjustments and don't do that on the fly.


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## onthewater102 (Sep 22, 2016)

This will be even harder to do hanging off the back as I'm going to have to mount it on a 12' v hull rowboat - there really isn't room for 2 people in the back.


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## Pappy (Sep 22, 2016)

I use a boat ramp to check timing. Leave the engine in the trim range, not in the tilt range as it will slam down. 
I back the boat down far enough so that the water line is below the ventilation plate (larger engines) and the prop tips will clear the water.
By allowing the prop tips to clear the engine will usually get fairly close to normal running RPM. Yes a wall of water will be thrown up so be aware of who is where and use common sense. 
Short cut for this is to set static timing about 2 degrees shy of your WOT timing before you start this ramp process. Normally you will be right on or a degree or so away.


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## onthewater102 (Sep 23, 2016)

That's two degrees retarded correct?

I'm working with a 20hp merc, so I can set the tilt to the highest peg and if that's not enough bring a block with me. Do you think I still need to get it so the blades are close to the surface of the water?

I've got a pond close to the house that has a concrete launch, with a very gradual grade where the concrete extends another 20' out along the bottom beyond where I'm estimating the motor will be immersed in the water, so I don't need to worry about blowing out the bottom during the test.


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## Pappy (Sep 23, 2016)

Two degrees retarded, yes. 
The ramp method is no exact science so you may have to experiment on static water height when you do it.
Enough to cover the water inlets, check for pumping, expose prop tips if possible to unload the engine and let it spin up under that reduced load. 
Am thinking your Merc has the water inlets pretty high up so check.........


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## onthewater102 (Sep 23, 2016)

You are correct - the water inlets are above the lower unit gearcase/output shaft housing section, and the impeller is higher still, so keeping the prop tips up toward the surface will be tricky, but if I back it in far enough and have a block giving me a bit more angle I should be able to do it still.

If I'm understanding you then the issue of just backing it straight down with the motor mounted/trimmed in a conventional position is that without the boat moving there won't be enough velocity to the water moving around the prop to allow it to reach full WOT RPM with a load?


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## wmk0002 (Sep 23, 2016)

onthewater102 said:


> If I'm understanding you then the issue of just backing it straight down with the motor mounted/trimmed in a conventional position is that without the boat moving there won't be enough velocity to the water moving around the prop to allow it to reach full WOT RPM with a load?



That's how I understood it.


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## Pappy (Sep 23, 2016)

Correct. In that configuration you are basically duplicating a test tank situation but without the proper test wheel. 
The prop has to suck air and slip or have the prop tips above static waterline to get up in the RPM range to check the WOT timing. 
Give it a try...nothing ventured nothing gained.


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## nccatfisher (Sep 23, 2016)

Back it in on the trailer if you have a ramp that you can do it and not be inconveniencing other boaters who want to launch and retrieve their boats. Just make sure you have plenty of depth.


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## onthewater102 (Sep 25, 2016)

Had the motor in a little too far but it didn't matter...timing gun was shit & wouldn't cooperate #-o only made it up to 3800 RPM in my 5 second test so I'll have to get it shallower next time. Plenty of water above the inlet and the tell was peeing just fine. The few flashes I got out of it looked like I'm 5-7 degrees retarded, but that was only a guesstimate because i didn't see it much more than twice.


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## CedarRiverScooter (Sep 25, 2016)

Why does the motor have to be under load to check timing? Isn't it just RPM related? As long as you don't over rev it, why not just do it in neutral?


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## Pappy (Sep 25, 2016)

CedarRiverScooter said:


> Why does the motor have to be under load to check timing? Isn't it just RPM related? As long as you don't over rev it, why not just do it in neutral?



Fair question.
The timing and throttle linkage has to be in the fully advanced position. (WOT)


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## CedarRiverScooter (Sep 25, 2016)

Thanks, I am used to inboard engines with centrifugal advance, wasn't thinking of fixed linkages.

Always learning . . .


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## onthewater102 (Sep 25, 2016)

CedarRiverScooter said:


> Why does the motor have to be under load to check timing? Isn't it just RPM related? As long as you don't over rev it, why not just do it in neutral?



BECAUSE PAPPY SAID SO THAT'S WHY!!!


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## Sinkingfast (Sep 25, 2016)

Here is one reason maybe..

My '76 15hp has an upper needle bearing and needs running clearance. And has points. When static checking the timing the magnet in the wheel forces the crank towards the head. When running the load changes 180 degrees on the crank. The points are not exactly 90 degrees from this movement. I have found the timing when not running is different then when running. Had to set the points differently from each other for the timing to be correct when running. 

Got a couple of atom point eliminators and all is good now.


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## Pappy (Sep 26, 2016)

Sinkingfast said:


> Here is one reason maybe..
> 
> My '76 15hp has an upper needle bearing and needs running clearance. And has points. When static checking the timing the magnet in the wheel forces the crank towards the head. When running the load changes 180 degrees on the crank. The points are not exactly 90 degrees from this movement. I have found the timing when not running is different then when running. Had to set the points differently from each other for the timing to be correct when running.
> 
> Got a couple of atom point eliminators and all is good now.



On the 1974-1976 9.9-15hp engines the outer plastic ring that locates the mag plate assembly is probably the culprit on the points gap/timing issue. You are sort of on the right track though. The magnets in the flywheel, when running, pull against the coil laminates and will change the gap in the points when the mag plate is loose. There was a bulletin to change out the original plastic ring for a newer Delrin ring. Stabilizes the plate nicely.


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## onthewater102 (Sep 26, 2016)

Getting that motor positioned relative to the surface of the water was very tricky. 1" too far in and there is too much load & I can only reach 5300 RPM. Pull the truck forward 3" and I don't have enough load & I spike all the way up to 6000 (target operating range 5000-5500). Spent more time adjusting the vehicle on the launch than anything.

Realized my issue with the timing light last time was my mistake - I forgot to ground the motor to the battery that was powering the timing light (pull start).

So after getting that squared away I was having doubts that I adjusted the timing on my 25hp on my boat correctly, same back & forth with the truck on the launch to get the prop load correct. Finally settled and adjusted it to 5800 RPM @ WOT with a target operating range of 5500-6000...I hope that's ok. I haven't gotten out with the new tach to see where I'm at on my boat with the 25hp and a 13P cupped prop - I'm hoping with the little tuning adjustment it should run that much better. I should raise the motor a smidge to get the cav plate to the waters edge while running so it isn't dragging.

One thing I noticed on my motor is the idle adjustment is kinda meaningless as there isn't enough rebound pressure in the timing advance to get the motor to idle under 850RPM. The trigger is advanced 2 degrees from where it should be at idle - perhaps I need a spring to draw it back? I don't see one on the other 20hp I was playing with tonight, but that motor the timing adjustment retarded enough at low speed that the fast idle marks on the flywheel required a little throttle to get them to line up from idle - my 25hp i couldn't find any adjustment that would let it slow down to 700 RPM without me pushing back on it with my thumb.

There is no pressure driving the idle adjustment screw against the stopping point you adjust it off of...ease up on the screw to lower the RPM and all it does is float out in front of the push plate. I even pulled the dashpot off the backside of the throttle cam to alleviate any pressure at all and I still couldn't slow it down. Not that it doesn't hold idle, but its rough as the timing is already advanced to where it should be running 1200rpm but the throttle is closed.

Perhaps my spring needs to be replaced (P/N 17 in the below linked diagram)

https://www.boats.net/parts/search/Merc2/Mariner/20XD%20%282%20CYL.%29/6443973%20THRU%200B238463/THROTTLE%20AND%20SHIFT%20LINKAGE%20%28ELECTRIC%29/parts.html


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## Sinkingfast (Sep 26, 2016)

Pappy said:


> Sinkingfast said:
> 
> 
> > Here is one reason maybe..
> ...



Yea, I've got the brown ring and I dimpled the pivot boss on the motor to tighten that area up. Thing is the upper crank race area measures no wear and I have tried 2 used and one new needle bearing and all have the exact same clearance at .0045in. So I looked up clearances for needle bearings and that falls where it should. 

I did install a spring on the mag plate to hold things from rattling around. That helped more than anything except for the Atoms. I was thinking about adding the charge coil to maybe balance out things but...haven't yet.

I guess timing error running or not, loaded or not is probably motor dependent.


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## Pappy (Sep 27, 2016)

There were other issues with that vintage of 9.9-15 as well. Some ran well and a lot did not. The engines following 1976 were fantastic in comparison.


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## turbotodd (Sep 27, 2016)

Use a test prop.


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