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Elliott000 · 30-05-2019, 10:58

Hey there guys, not sure if I should post this here or in the electrical forum so feel free to move it !

I'm trying to help my buddy get his MD2 back in his sailboat. Hes done a bit of messing around with the wiring and cooked a wire in the original relay box.

I'm more of a new school guy, can we upgrade this old relay/solenoid box and clean up the wiring relatively easily? It shorted the lead because he jumped the relay and went to ground. Ill attach a couple pics of what im talking about. He is even interested in ditching the stock volvo penta panel and just going push button, The plan is to relocate the starting panel to inside the vessel, We will keep the key cylinder and then just roll with a push button start. However im unfamiliar with these systems and im curious why there is a key for on/off, then a toggle switch which goes in/out at the center plus the push button.... I figured it would be key on, push too start. Whats the center toggle for?

Thanks for any help guys

DougR · 30-05-2019, 12:12

So, your buddies old MD2B engine is equipped with a "dynastart", which is a DC generator that also doubles as the starter motor. When the unit has DC current fed to it, it functions as a DC motor and starts the engine, but when it is driven by the belt, it produces DC current. The relay box which he fried did double duty......a start relay and also a charge regulator.

Even when the relay box was current product it was a bit of a fragile item, and it was replaced by a separate start relay and a more conventional voltage regulator. You can get the part numbers for these two items in the MD2B parts book, but it's anyone's guess whether they are still available from VP. However the start relay was a simple stand alone high current relay, available anywhere and I would guess you can get a DC generator regulator at any decent automotive electric shop.

Your guess about the start function is correct....turn on the key and press the start button. Easy Peasy... The extra toggle switch in the center of the panel is exactly that, an extra switch in case you want to drive something else while the engine is running, like an engine room blower. In fact there are two green leads coming off the key switch, one goes hot immediately and connects directly to the buss connector, and the other is controllable via the toggle switch.

Hope this is helpful.

DougR

Elliott000 · 30-05-2019, 13:26

That's an awesome explanation thank you Doug. Ill dig around for a dc relay deal. Is that a critical piece of the puzzle if we cant get that working right away? His engine does have a traditional alternator on it as well to take care of charging the vessels battery and some accessories. Just curious if i can run the starter relay and get him going then try and dig up ancient or hard to find stuff to sort out the dc generator in a few weeks time.

Thanks

**roverhi** · 30-05-2019, 15:24

If you just want to get it running disconnect the belts to the Dynamotor and hand crank it. Push down the cold start button at the rear of the engine/transmission, lift the compression releases, crank like you meant it, drop one compression release when you get max crank rpm, it should fire on one cylinder immediately then drop the compression release and Bob's your uncle. Hand cranked our MD2 for 10 years after the Dynomotor broke the mount bolts and fell off. Engine was fitted with an alternator so didn't need the Dynamotor once the engine was running.

Still have a hand crank for the MD2 if you need it.

DougR · 31-05-2019, 05:04

Go online and do a little bit of reading about the Bosch Dynastart. I'm pretty sure you can use just the starter function as you have the alternator for battery charging.

There is also some indication that the damaged wire in the right lower corner of your photo is actually a fuse link, and replacing it might bring things back to life.

DougR

Bycrick · 31-05-2019, 13:57

Years ago, I had an MD2B with separate factory installed alternator and starter motor. The Dynomotor was old even in 1975 when the boat was built.

jaylo264 · 31-05-2019, 15:54

We have an MD1 with similar dynastart -- Lucas UK rewound and refurbished it for us, before they went t's up, it;s still perfectly working, started the ole md1 today and it runs BETTER than the new D1-20 on the bigger boat.

Easy to hand start. But if battery ok, press brass cold start, comp lever up, put key in, turn, blue and red lights come on, press button and after a little while to pump up the diesel, away she goes!
Rush out of the saloon to throttle back!

The reason I'm mentioning this is that I SO prefer my old dynastart/volvo panel/ MD1 to the new volvo engine : PLEASE keep them! They will last for ages -- my set up is from 1965. Boat fine, all fine, and I trust them. Don't trust the D1-20