4.3 liter Mercruiser won't go over 1500 rpms

[gwgman566]

I have a 4.3 liter that is a reman. It has a GM CD distributer. It will not advance the timing under load. I have checked the module at Advance Auto parts and they say it passes all the test. This distrubuter has three wires coming out of it. On one plug is a black wire I believe goes to the cut-out switch. The other two are brown and pink, they run to the coil. Is there supposed to be something else in the mix? I am scratching my head at this point. I can add that the cut out switch is an older version and am wondering if this could be the problem maybe I need the newer type that is now on Mercruiser boats. Any help would be appreciated. I can also say that there are no external modules or amplifiers just the parts that I named.

 

[WillyBWright]

Re: 4.3 liter Mercruiser won't go over 1500 rpms

Welcome to iboats.<br /><br />HEI instead of Thunderbolt? That might be the problem in a nutshell. I expect it needs RPMs to advance the timing. If it can't get the RPMs, it probably won't advance. Sort of a Catch-22. Needs RPMs to advance, but won't get more RPMs unless it advances. The advance curve is probably all wrong for a marine motor.<br /><br />As a rule, ventilated props don't work on stern-drives (or 4-strokes in general). In your case it might be worth trying. That'd get the pre-planing RPMs up so the spark can advance.<br /><br />How'd you end up with HEI in a MerCruiser? I've heard of it being done, but a car distributor in a boat could be a real explosion danger. I can't imagine it'd meet marine requirements.

 

[gwgman566]

Re: 4.3 liter Mercruiser won't go over 1500 rpms

This distributer is a Delco style but sold by Marine Power. So it is a "marine distributer" The instructions that came with it showed hooking up the black wire to the cut out switch. So in a nutshell it is a marine distibuter.

 

[akriverrat]

Re: 4.3 liter Mercruiser won't go over 1500 rpms

was this a replacement for a points ignition?

 

[gwgman566]

Re: 4.3 liter Mercruiser won't go over 1500 rpms

No this engine is new and we bought all the parts for it and then replaced a 3.0 liter with this motor. We went from OMC to Mercruiser also. It will go over 1500 rpms under load if I turn the distributer by hand advancing the timing manually. But we all know that isn't any fun. Its seems to be stuck in its "initial timing" phase. This is the type of distributer that you have to connect a jumper wire to do an initial timing at idle speed. Timed at 8 degrees BTDC, then you should be good to go. It absolutly will not advance the timing by itself. I was wondering if the cut out switch is defective or not compatible. The cutout switch came off of a boat that had the Thunderbolt IV ignition.

 

[Bondo]

Re: 4.3 liter Mercruiser won't go over 1500 rpms

Well,<br />I haven't seen 1 like yours.....<br />Seems to me, You should have "something else in the mix?"...........<br />The Cut-out Switch will Totally Cut the Power..... Nothing to do with Advance......<br /><br />Maybe you should be talking to "sold by Marine Power."......... <br />I'm Sure they can answer your Question..........

 

[akriverrat]

Re: 4.3 liter Mercruiser won't go over 1500 rpms

the cut out switch for this system should be wired to provide 12 volts to distributor. that is why i asked about points; where cutout switch goes to ground. not that this has much to do with the timing not advancing anyway. try pulling the larger of the two plugs off the distributor. if timing still doesn't advance you probably have a bad module.

 

[mstrhntr]

Re: 4.3 liter Mercruiser won't go over 1500 rpms

First off you need to be sure that your timming is not advancing rather than advancing to much. Not sure how old the ditributor is but you might take a close look at the fly wieght springs! Just a thought

 

[gwgman566]

Re: 4.3 liter Mercruiser won't go over 1500 rpms

Fixed the problem, New module from GM solved the problem. Don't trust a test at local auto parts store. They were wrong. By the way thanks for everyones help.