Severe Detonation and overheating

Hi guys, first time post. Long time reader of other posts. I've searched and searched and can't really find anyone with my problem so here goes..

1986 3.0 Liter GM 140

I have a very severe detonation problem. It will only stop after the timing is adjusted to about 6* ATDC. And according to the book, timing should be 6* BTDC. It also overheats when adjusted to 6* ATDC, but I think that may be a different issue all together, because the temp goes down when turning right and goes wayy up when turning left. I don't understand how that could effect it but it does, drastically at that, were talking a 60* (140*-200*+) difference in temp here.

Thank you very much for your help through the years.

Re: Severe Detonation and overheating

Set your timing to spec. not sure what it is since you don't mention if it's OMC, Mercruiser, or what distributor, and then check to see if your advance is working.

Re: Severe Detonation and overheating

It's a mercruiser. What should the timing be at full advance?

Re: Severe Detonation and overheating

24? to 29? (NOT counting initial timing)

Here is a link to the OEM manual you can download to your computer. About 150MB. The section on ignition explains it further.

http://www-alt.mercurymarine.com/mnetdata/SERVICE/CRUISER/Servmanl/10/cover.pdf

Re: Severe Detonation and overheating

Thank you I actually have the book but its at the lake with the boat, and I'm at home with the internet

But since knock is caused when the timing is to far BTDC then if it was the advance wouldn't that have to mean that its advancing too much? is that possible? And since it has to be set ATDC to not knock. Thank you for your time.

Re: Severe Detonation and overheating

anythings possible.....

1. check your timing/advance....
2. check your fuel for signs of water.....
3. check your compression....