TPS issue

[old-colt]

I am working on an older Yamaha Excel outboard that the TPS has gone bad. The replacement is stupid expensive. Here is what I am up against,
The original TPS is about 1K ohm across it's range. I am finding this to be rather rare.
The newer outboards use a TPS with a 4.7K range and I am finding this more common in the few cars I have paid attention to.
1, anyone know of a source for a TPS with about a 1K range?
Or,
2, Would adding a resistor in parallel across the ends of a 4.7K TPS allow it to function with a computer looking for a 1K range?

This is on an engine that uses a crank sensor on the flywheel and TPS for setting the timing.

[billr]

Have you tried a 4.7K pot? I think it is unlikely the input that pot feeds has an impedance low enough that the difference between 1K and 4.7K would matter.

Edit: a resistor in parallel across the "ends" of the pot will make no difference, except to draw more current from whatever the pot Vref is.

[LAV1000]

if the TPS input uses a voltage signal the 4.7K should work.
Otherwise get the cheapest potentiometer from an electronicsshop and test it.

[old-colt]

I did run a short test with the 4.7K. I can not rule it out as being viable. The engine was still low on power but as do more inspecting it may not have been that TPS / timing causing all the issue.
It is difficult to verify the timing since the engine needs to be under load and in order to do so kind of need a full hard bottom boat launch where I can run the boat in gear strapped to the trailer. Difficult to achieve near here, I will find a way.

[billr]

I should have asked in the beginning... is the original a 3-terminal device, and is it used as a pot (all 3 terms connected) or is it used as a variable-resistor (wires to just 2 terms)? My previous answer was predicated on it being used as a (3-term) potentiometer.

[old-colt]

Yes, full 3 term.
The original just did not sweep well with a meter on it, quite jumpy which appears to be the major issue with this old analog system.
This morning I have remounted the 4.7K and run the engine on a hose. I will next run it in a small pond to see if the carbs need setting up again as well as put a timing light on it.
One thing I am not sure about currently is this TPS sweeps from .51V idle to 3.78V full throttle, I expect to see 4.5V full. The service docs do not show a spec for the range.

[DaveEFI]

In theory, a 90 degree pot should be fine. But in practice, most seem to be more like 120 degrees or so. So won't give 0-Vs volts out.

A good check for a TPS is to wire it up as a pot between CD player (or whatever) and power amplifier, and play some music. If it crackles or breaks up when you move it, needs sorting.

[old-colt]

A good check for a TPS is to wire it up as a pot between CD player (or whatever) and power amplifier, and play some music. If it crackles or breaks up when you move it, needs sorting.

I like that, that is new to me.