Fuel Pump & Glow Plug Circuity is differant !!

[Ron Hill]

Guys : The M25 & M25XP have completely different (separate) circuitry for the aux electric fuel pump (lift pump) & oil pressure switch than the M25XPB, M35A and M35BC engines.

Not too sure if OSHA got involved, but I suspect it!

I first got questions from a 1993 M35A (30hp) owner.  His engine was made by Universal (Westerbeke) after it was taken over from Oshkosh in the early 1990's. He noted that the lift pump was wired into the "spring loaded" glow plug post on the key switch.  My first answer was that Poco at the factory, put the connection on the wrong post!

Then the question of the double pole on the oil pressure switch came up !??!  
I've written this up before, but here it comes again:
With the ciricuitry of the double pole oil pressure switch - here's what happens.  The key switch is turned ON, no fuel pump is activated until the key switch is turned to the spring loaded position which also activates the glow plugs.  The glow plugs heat (warning not to exceed approx. 20 seconds or they'll burn up!!) and the lift pump pumps fuel to the injection pump.  When you release the key from the spring loaded position the fuel pump cuts off and will only start back up after the starter is hit, the engine is running and there is oil pressure.

The entire idea behind this circuitry is so that when the engine loses oil pressure, the lift pump will cut off causing the engine to to stop.
The only problem is that the C34 has a fuel tank that is higher than the engine and the gravity flow of fuel will keep the engine running.  That's why there are 2 (+) connections on the oil pressure switch!!

Owners have to realize that there are 4 different engines in the C34 production and a fifth if you repower with an M25XPB like I did.

 A few thoughts

[Stu Jackson]

I'm always giving advice, and links, too.

Here's one:  Hard Starting & Glow Plug Problems:  http://c34.org/bbs/index.php/topic,3347.0.html

It's LOOOOOONG and starts off with a completely different issue, but gets around to the discussion of the different wiring schemes and the totally WRONG because they're DIFFERENT wiring diagrams in the documentation from the ENGINE builder on page 3 and then on to the end of the topic.

Just my conclusions from a nice discussion trying to help people without preaching  bout how we'd answered the same question before.  Lots of stuff comes up time and time again.  People keep getting new-to-them boats all the time.

I've been out on our boat for two days (three days and two nights, wanna make a movie?) and can't be happier.  Great sail on single reefed main only through 0.22 NM visibility with a high speed catamaran ferry crossing in the fog with it unusually on the deck, glad that darned radar reflector works.  San Francisco Bay's Vessel Traffic Service is extremely good at reporting major local traffic, and because it was a Friday morning the fisherman weren't out.  Max speed SOG 7.4, average 4, but a beautiful day.

Oh, and I got the puck GPS and got it to work with the laptop!  I'll fill that in in the computer navigation thread I started some time ago.