Starter Issues

[Seabrink2006]

Greetings All,
I have an '84 Cat with the 23HP three cyl diesel, and have been having some issues with the starter. The engine started very strong for the past two months, and now i can barely get the thing to turn over. It still turns, just incredibly slowly, and nowhere near strong enough to get the engine to fire. I originally started at the batteries, thinking they surely must be drained, but when i checked them against my volt meter, they were a strong 13.45 volts, hooked in parallel, and producing almost identical charge when i disconnected them from each other. After checking the 12 volts, i decided to follow up with my 6 volt house bank. These were also producing roughly 6.8 volts, so all batteries are perfectly healthy, and it must be something else. I checked the transmission next to make sure i wasn't spinning the shaft while trying to start the engine, fortunately i wasn't, but now i find myself truly puzzled as to what the issue could be. I'm afraid that it could be an electrical short, but thought that if a short did exist, then the starter would just not react at all. I would prefer not to have to take out the starter for a rebuild, but it looks like i'm running out of options. Please let me know if anyone has any advice or recommendations, i really appreciate your input. Y'all have a nice day.

 

[jrowan]

The most logical conclusion I can make based on what you've stated is that you have a voltage drop from the batteries to the starter circuit, likely due to corrosion or bad wring connections either at the battery terminals or at the starter, or a combination of both. Grounding cables especially suffer corrosion, as they are usually bolted down to metal that is low in the boat, near bilge water corrosion.
If you have the original wiring harness with an Amp meter installed at the engine panel, it is famous for draining voltage. This is due to the problem that the inline amp meter has wiring from the battery circuit going to the meter in between the starter & alternator which creates an additional 8-10 feet of cable going to the meter & back again from the cockpit mounted guage. Seaward & Catalina direct sell a newer version of the wiring harness that eliminates this bad source of voltage drop, & uses a newer volt meter instead of an Amp meter. I still have this set up on our C 30, but I've found that as long as I have good, clean connections & STRONGly charged & healthy batteries that I can overcome this. Your batteries may also initially register 13 +volts, but if you can read the voltage drop when the starter is engaged, you will likely see a significant voltage draw & subsequent drop. The only thing that I'm not sure of is can you mix both 6 volt & 12 volt batteries on the same charging circuit? or can this damage the 6 volt batteries? Anyway, food for thought.

 

[Stu Jackson]

Check the engine ground wire, back side off the bell housing. A poor ground will give that kind of problem. Also check the electrical connections at the starter.

We have a lot of M25 engine information on our C34 website, you're welcome to it

http://www.c34.org/wiki/index.php?title=Diesel_Engine

and Critical Upgrades which includes a lot of engine information

http://c34.org/bbs/index.php/topic,5078.0.html

 

[DanM]

Sea,

So many of us have struggled through this issue with our C30's, myself included.

I'd offer this advice. Resistance is likely your problem, Catalina used #4 SAE cable to the starter and ground, which, probably 25 years ago was just barely adequate (though not acceptable at todays standards). Add 25 years of wear and tear and resistance becomes an issue. I paralleled another #4 AWG (both positive and negative) to solve my problem, but in hindsight I wish I would have just replaced with a #1/0 AWG and been done with it, but, alas, a project for another day. I also went through the typical new owner issues of blaming the batteries and the charger before fixing the wiring, trust me, fixing the wiring first is the way to go, even if you do have a bad battery (or two). The #4 SAE wiring is, or will be at some point, a problem, it's just too small.

Also, I can't recommend highly enough Nigel Calder's "Boat Owners Electrical and Mechanical Manual". Nigel will teach you how to use a multi-meter, explain how your electrical system works, and then give you a step by step procedure for checking for voltage drop (resistance) in your starting circuit that will likely show that the #4 SAE wiring is undersized for reliable starts. His book is money well spent in my opinion.

I have a chart showing voltage drop in my ships log now (based on Nigels instructions) so that if I ever have to troubleshoot the starting system again I know exactly what my starting circuit health was when I did the improvements and (hopefully!) I'll be able to make repairs quickly if I ever need to. Great book.

Best of luck, let us know how it works out for you!

DanM.