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PostPosted: 22 Sep 2016, 10:32 
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Location: CT
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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PostPosted: 22 Sep 2016, 10:58 
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onthewater102 wrote:
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.

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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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PostPosted: 22 Sep 2016, 11:17 
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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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PostPosted: 22 Sep 2016, 11:52 
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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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PostPosted: 22 Sep 2016, 11:55 
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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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PostPosted: 22 Sep 2016, 21:36 
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[size=150]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.
[/size]


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PostPosted: 23 Sep 2016, 08:49 
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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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PostPosted: 23 Sep 2016, 09:29 
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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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PostPosted: 23 Sep 2016, 09:38 
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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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2002 Alumacraft 1436LT w/ 1984 Mariner Tiller Converted to Remote & 55# Minn Kota Terrova 12v (removable)

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PostPosted: 23 Sep 2016, 10:20 
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onthewater102 wrote:
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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PostPosted: 23 Sep 2016, 18:15 
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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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PostPosted: 23 Sep 2016, 22:14 

Joined: 04 Feb 2013, 22:11
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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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PostPosted: 25 Sep 2016, 02:26 
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Had the motor in a little too far but it didn't matter...timing gun was s**t & 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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For Sale - Custom Hand Tied Jigs, Bladed Jigs,Custom Rods

2002 Alumacraft 1436LT w/ 1984 Mariner Tiller Converted to Remote & 55# Minn Kota Terrova 12v (removable)

1985 Bass Tracker III - Restoration w/ 1988 Mercury 60hp
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PostPosted: 25 Sep 2016, 09:22 

Joined: 13 Nov 2014, 08:01
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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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PostPosted: 25 Sep 2016, 09:25 
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CedarRiverScooter wrote:
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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