260A - Aquamatic 250

Had a nice first outing last Friday, but today the mechanical lift motor for the outdrive doesn't turn. The relays click in both directions but the motor doesn't even grunt. I see two allen heads attaching the unit to the housing. Is there anything tricky I need to know about pulling the assembly out of the boat. I hate to think about $500 for a used unit - maybe I can rehab this one? If not which ones will fit?

Also - I replaced my points distributor with an EST model a couple years ago. I set the timing at 8° with the gizmo/shunt attached. Today I checked the timing and it maxed 35° at 3,000 rpm. So I reset the timing without the gizmo at 29° for 3.000 RPM. Is there anything wrong with this practice?


Lastly - what's the 'tunnel' for on the timing tab that's below the zero notch? That little tube?

That tube I believe is a factory fitting to set the timing you just use the timing marks. If the base timing had changed it is possible the harmonic balancer moved you need to use a piston stop tool to confirm true TDC. Then you can properly set the max spark advance the way your doing. Dont trust the balancer TDC is too important on a marine application.

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jeffnick said:

Had a nice first outing last Friday, but today the mechanical lift motor for the outdrive doesn't turn. The relays click in both directions but the motor doesn't even grunt.

Check for voltage at the electric motor terminals while the Up/Down switch is being operated.

I see two allen heads attaching the unit to the housing. Is there anything tricky I need to know about pulling the assembly out of the boat. I hate to think about $500 for a used unit - maybe I can rehab this one? If not which ones will fit?

Loosen and remove the two cap screws.
Raise the drive enough to place a piece of soft wood between the Vice Rod's "pressure plate" and the corresponding "arm" on the main suspension fork.
Push down on the drive.
The uplifting pressure should push the electric lift-out unit out of it's bore.
DO NOT use any type of wedge between the mounting flange and the transom shield!The lift-out unit housing is cast iron! It is rather brittle and will likely break if you attempt to do that.


Also - I replaced my points distributor with an EST model a couple years ago. I set the timing at 8° with the gizmo/shunt attached. Today I checked the timing and it maxed 35° at 3,000 rpm. So I reset the timing without the gizmo at 29° for 3.000 RPM. Is there anything wrong with this practice?

First off...... 35* BTDC @ 3k rpm is a recipe for Detonation.
29* BTDC @ 3k rpm is still a bit aggressive...... I'd prefer to see 29* @ 3.4K rpm.


Lastly - what's the 'tunnel' for on the timing tab that's below the zero notch? That little tube?

Click to expand...

kimcrwbr1 said:

That tube I believe is a factory fitting to set the timing you just use the timing marks. If the base timing had changed it is possible the harmonic balancer moved you need to use a piston stop tool to confirm true TDC. Then you can properly set the max spark advance the way your doing. Dont trust the balancer TDC is too important on a marine application.

I agree..... if the outer balancer ring has slipped against the inner hub, checking/adjusting ignition advance while using these markings will be impossible.
I would do as Kim suggests and verify the #1 TDC by using a PPS...... (positive piston stop).

Use caution if looking at YouTube videos for this procedure.
I see mistakes and misinformation in some of these.


This guy uses the crankshaft bolt to rotate the crank (be very careful if you do this).
NOTE that he says; DO NOT use the starter motor once the stop is installed. (perhaps disconnect the battery)
He DOES NOT use a degree wheel, but he does show us the basics by making marks that will eventually be split!
https://www.searchencrypt.com/videos?eq=7LNL1El29EV%2BeTOk4caYWqrWz3UCx%2B8EYHxIpKJD5m0ibMoYZJMJa079CUX%2Bir6Y




This guy uses a PPS via the spark plug port (see video @ 32 seconds)
He correctly shows us how to use the degree wheel and temporary wire pointer.
He has adjusted the PPS to stop the piston at approx 17* BTDC. (I prefer to use 30* +/-)
He shows one stop @ 17* and one @ 16*.
He then splits this (16.5*), giving him true TDC @ ZERO once the stop has been removed.
At that time he will correct the markings!
https://www.searchencrypt.com/videos?eq=jMAzfFYIx2kZbvflv1ZGenXI2f%2FTL%2FgaoRU4ZYG%2BA0uC1zlWrkDPLHXozOVtLz0z



Re-Cap..... the PPS will stop the piston at the same crankshaft angle in either direction.
The goal is to find the two stopping points (crankshaft angle), and to then split these stopping points in terms of crankshaft angle (degrees).
When we split this (with the PPS tool now removed), we now have true #1 cylinder TDC.
This is when we make any corrections to the original markings.

Click to expand...

I have a question.
Your thread title says; 260A - Aquamatic 250

The 260A was never used in front of the 250 drive!
Just curious...... what going on?



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Thanks guys. Nothing has slipped - maybe I just screwed up when I set the timing after installing the EST stuff with the shunt. We almost never go over 6-8 mph in the houseboat so the only time I might notice any problems is when I open her up every now and then - and she stumbles above 3,000 so I never keep her up there for long. Now I know what the cause may be.

Also, I ran the motor up to about 4k - the timing with the EST was the same at anything above 3k. Is this something I should look into?

The boat is over 40 years old. I'm thinking it was originally a stringer with an OMC drive - I know some were built that way and there's filled holes in the transom that look like the OMC steering pattern. Anyway, the drive now has a 250 cover and no threads on the prop shaft. Who knows what this drive really is? It's obviously not original.


Here's the 260A.


And good thinking on checking the voltage at the tilt motor Ricardo. I'll do that today. Maybe it's electrical and I won't have to pull it after all.

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jeffnick said:

Thanks guys. Nothing has slipped - maybe I just screwed up when I set the timing after installing the EST stuff with the shunt.

If the harmonic balancer's outer ring has slipped on it's inner hub, the PPS procedure will let you know.

We almost never go over 6-8 mph in the houseboat so the only time I might notice any problems is when I open her up every now and then - and she stumbles above 3,000 so I never keep her up there for long. Now I know what the cause may be.
FYI..... in a heavy boat like this, Detonation is a greater threat even while @ only 3k rpm.

Also, I ran the motor up to about 4k - the timing with the EST was the same at anything above 3k. Is this something I should look into?
Many advance curves will be "full in" by 3,500 RPM or so. There is no need to further advance the spark lead much past this rpm.

The boat is over 40 years old. I'm thinking it was originally a stringer with an OMC drive - I know some were built that way and there's filled holes in the transom that look like the OMC steering pattern. Anyway, the drive now has a 250 cover and no threads on the prop shaft. Who knows what this drive really is? It's obviously not original.

If there is a metal fitting in the suspension fork (A) and an oil port at the lower area of the Intermediate housing (B), then it is likely a 250.

Click to expand...

Good call on the voltage Ricardo. My lift fuse was blown. Might be something going on to blow it, but for now we're back in operation with no hesitation or funny noises.

As for the drive...looks like I have the metal at "A"


but no drain plug?


I'm going to see what the timing is at 3500 - it just hurts to rev it that high without a load? Then I'll use the gizmo to check it at idle.

Follow up...

Good call on checking the voltage at the lift motor Ricardo. Big THANKS!

On the EST front...
I ran the engine up to 3500 and she stayed at 29°.
I then connected the shunt to check the base timing - it was 8° within 1/4°. I didn't mess with it.
So for me anyway, it looks like either method works to set the timing - I'm guessing I screwed something up when I set it initially. I guess I'm lucky that I didn't put her under much of a load (for long) with the timing advanced too far...hope there was no permanent damage.

Hope to get out in a week or so to see how she behaves at higher RPM. Maybe I'll like going faster - she's supposed to do 30mph.

On the EST front...
I ran the engine up to 3500 and she stayed at 29°.

Click to expand...

jeff, the ignition advance will/should be progressive.

example only (not per any specs):

8* at idle rpm
12* at 1,400 rpm
18* at 2,000 rpm
22* at 2,400 rpm
26* at 2,800 rpm
etc, etc!

at around 3,200/3,400 or so rpm, the advance will cease to increase.
This is the “Full In” rpm.


again...... example only!

I can see the timing increase with rpm although I didn't check it at different times. It appears to max out at 3000.
If the base timing checks out too I've got to think I'm OK.

Drain plug on that drive is a screw at the very bottom of the lower gear housing ( towards leading edge). Replace washer every time you remove the drain.