Mercruiser 260 Timing ????

[jhitt]

1987 Mercruiser 260... the book says timing should be set at 8* BTC, but someone before me replaced the points with a pointless ignition.

At 8* I get nothing in the water, and runs fine without a load. I advanced the distributer and set it by ear in the water, but I'm only getting 4100 RPMs at WOT.

Does anyone know what degrees I should set it at AND just like a car, Is there a wire or wires I need to short while setting the timing.

thanks....

 

[6meter]

Re: Mercruiser 260 Timing ????

I have an '86 260 with a pointless Thunderbolt IV ignition. Standard issue. Factory. 8* BTDC.
What type of replaced pointless ignition do you have?

 

[Bondo]

Re: Mercruiser 260 Timing ????

Ayuh,... Your motor Never had points igntion, it came with T-Bolt IV igntion...
T-Bolt IV is plug, 'n shoot timing,... Nothing to plug or unplug to it...

Set the timing to 8?btc, then figure out whatever else is Wrong with it....

 

[jhitt]

Re: Mercruiser 260 Timing ????

I do think mine is Thunderbolt IV too, but the pack in the distributer has been replaced... Maybe just a replacement...I might have to go back and read some more...I could have missed something.

But, at 8*, it's dead in the water. NO increase in RPMs, NO power, nothing.

Is there something I need to connect or disconnect to set the timing?

 

[jhitt]

Re: Mercruiser 260 Timing ????

now I'm really lost........I know it was at 8* BTC

 

[Bondo]

Re: Mercruiser 260 Timing ????

Ayuh,... Do a Compression Test,... Maybe the motor is just plain ole Whooped...

 

[6meter]

Re: Mercruiser 260 Timing ????

If the timing is set at 8* and doesn't run good, you have other issues. Could be electrically related, fuel related, mechanical related. You have to determine.

 

[Aloysius]

Re: Mercruiser 260 Timing ????

It's all about TOTAL timing at speed. You want at least 30 degrees advance at no more than 3000 rpms. I run 36 degrees total on my small block Fords, and don't even know what the initial is.

Initial timing settings only work when the advance in the distributor is known.

 

[funk6294]

Re: Mercruiser 260 Timing ????

If you are setting the timing and finding it is not correct, it could be that the harmonic balancer has slipped on its hub, or even broken the key. This would make the timing off when you set it. For example if you set it at 8 and it had slipped, it could be actually at -4 degrees or other. Since you say that you can get it running better by adjusting the timing by ear, I would manually determine the TDC on the engine and ensure that the timing mark on the balancer is correct.

 

[Aloysius]

Re: Mercruiser 260 Timing ????

excellent point Funk.

 

[Don S]

Re: Mercruiser 260 Timing ????

Here is the advance curve your TB4 distributor should have.

 

[Aloysius]

Re: Mercruiser 260 Timing ????

30-34 degrees total sounds ok , but that curve is pretty slow. Add 8 degrees initial to the 22-26 degrees in the distributor gives this MAXIMUM advance number.