CONDOR24

Hey guys, question - I upgraded my boat's power from a 350 mag. to a 502/502 clone. I reused the thunderbolt IV module and distributor. The part # on the module is 8JO9A V8-24 , Is this module compatible for use on the 502? the reason I ask is the motor still cranks hard after 30+ hrs of use. Total advance set to 34 @3000 rpm. ANY IDEAS ?

Crazyhorse

You've got a 24 degree module so your initial advance is 10 degrees if you have 34 degrees total advance. It should spin right over at only ten initial. What rpm are you using for checking the total advance?

CONDOR24

total advance set at 3000 rpm. i did purchase a new gear reduction starter which i'm putting in while motor is out for winter.

blue thunder

What do you mean by"cranks hard"?

Dave

MACDAD260

At 3000 rpm you're not at full advance. You need to run the engine up until it stops advancing and then adjust the distributor untill you get the timing where you want it. I have the same setup and it is not at full advance until about 3600-3700 rpm. It sounds like the engine is going to blow at that speed but, it won't. Like Crazyhorse said. If you set the initial advance at idle to 10* you should be right on or very close.

CONDOR24

By cranking hard I mean it turns over very slow, especially when hot. Ive replaced the alternator with a high output 110 amp, put 2 new group 27 marine batteries, still same dilema. It takes both batteries to start when hot. The one thing I did notice at the end of summer was with the plugs out, she still cranked hard, which led me believe maybe the starter is the problem.I bought a new one, but never installed it while the motor was in the boat due to header/stringer clearance. So now the motor is in my garage, I'll swap the starter and hope for the best. I wanted your opinions on my ignition module for process of elimination. thanks!

BadDog

Load test your cables. Battery switch can also cause a significant drop if corroded.

Crazyhorse

I can't really say mine rolls over hard, but it doesn't spin as fast as it should, mostly due to the fact that Cigarette put about a mile of starter cable in these older boats. So while I've got my engines out I'm going to reroute all the starter cables.
If you set the timing at 10 degrees initial at 650 rpm, assuming it will idle that low without killing, you will be right on 34 degrees at maximum advance just like Macdad260 said.

mcollinstn

#1) You have a 24 degree module. Set the static timing at 10 degrees. You are probably close to it now, but if you've set max to 34 at 3000, then you could be as far off as 14 static.

#2) it cranks hard with the plugs out. You just told me all I need to know. It ain't got nothing to do with timing.
#3) It's worse when hot. It still ain't got nothing to do with timing.

Before you crunch your body in odd shapes to put your new starter on, do a test on your electrical connections.

a) Flip off the kill switch. Crank the motor for 20 seconds.
b) immediately start at the battery and feel for hot cables. Feel down the length of the cables to the Perko switch if you have one, and then from it to the starter and block ground. Take note of any place that the cable is hot - this indicates a bad connection. Bad connections heat up and the cable will be hot near a bad connection.

If the cables are all evenly warm, and the starter is hot, then it is certainly and definitely the starter.

A dragging starter will run hot, which makes it drag even worse. Heat compunds the issue whether it is from engine heat or starting current.

If you got a new starter, please make sure it is a marine starter.

Keep in mind that you can have your marine starter rebuilt for $11 more than a car starter and it should have no problems spinning your motor. (some shops charge the same for a boat starter - some charge $100 more - the parts are an additional $11 in the gasket and end bearing.)

Crazyhorse

By the way, some of the cheaper battery switches have a very low amp rating. Buy a good one or do without.