MD7A Oil Change

[S/V Ethan Grey]

I'm changing the oil in my CD30 with the Volvo MD7A.
From what I can tell, there are 3 systems with oil:
1. the engine itself
2. the reverse gear
3. the reduction gear

I have sucked out the oil in the engine through the dipstick and replaced it with Shell Rotella, SAE 30. No problems there except SAE 20 is actually recommended per the manual.

I just realized where the reverse gear dipstick is (1" bolt head looking thing that you have to unscrew). From the manual, it looks like I need to suck that oil out from its dipstick area and fill with the same oil as in the engine (SAE 30 in my case). Please let me know if that is not correct.

From reading the manual, I think the reduction gear oil system is shared with the engine oil system, which makes me think that since I changed the oil in the engine, I don't need to do anything with the oil in the reduction gear. But then I wonder why there would even be a dipstick for the reduction gear. Am I missing something here? Do I need to suck out the oil in the reduction gear as well? Wouldn't that just suck out the oil in the engine that I just put in there?

Thanks in advance for your help. -david

[mgphl52]

My MD7A is in my CD28 without the backwards mount.
I only change the engine oil and the trans oil.
Do you actually have a separate case from the transmission for a reverse gear?

[kerrydeare]

My MD7A is in my CD28 without the backwards mount.
I only change the engine oil and the trans oil.
Do you actually have a separate case from the transmission for a reverse gear?

This is quite the case. The "reverse gear" and the "transmission" are combined in this system and it's really only necessary to change the "lube" oil (i.e., the main dipstick) and the oil contained in the trans, which itself has its own dipstick. The trans oil is known to remain viable for a very long time since there is no exposure to the combustion process for this fluid.

If I'm not mistaken there are online copies of the owners manual and the shop manual for the MD7A. Mine went with the sale of the boat, but I'll dig around for a scanned copy.

EDIT: Just noticed you are working with a v-drive engine that, as pointed out below, does indeed have 3 separate oil reservoirs. Sorry.

[JD-MDR]

I just went through my gears and found that some oil does flow from the crankcase to the reverse gear. but not much it barely registered on the stick. The manual says they share the same oil so I figured I only had to pump the oil out from the crankcase. Wrong. I've had this boat for four years and ran it 700 hrs I didn't know that stick was there because my exhaust muffler was mounted right on top of it. I fixed that. When I had the reverse gear off I flushed it out real good and found a lot of thick crud. I will from now on drain that oil from the plug on the bottom. I don't think a pump from the dip stick hole will get all the crud out. Some times, on previous boats, I even flushed it out with diesel oil. I'm thinking that by the way mine was covered up with the muffler I'll bet the oil in the reverse gear had never been changed or even been checked. I now have a rebuilt v-drive. I think that is also the reduction gear. I motored across the Santa Barbara Channel and back this weekend 8 hrs total and It feels and sounds really nice. BTW my v-drive is completely separate from the reverse gear and engine. I luckily got a response from a guy on the cruiser forum who was very informed on MD7A gears.
I better take some of that back. I don't know how much oil flows from the crank case to the reverse gear because in my case some was flowing down hill to the v-drive but never drew much more than about 8 oz. from the crankcase. I do know that when I removed the reverse gear oil poured out from the engine. Luckily I had a plastic pan under it.

[S/V Ethan Grey]

Thanks everyone. I changed the reverse gear (transmission) oil this afternoon. I put in SAE 30 Shell Rotella as that’s what I used in the engine. I think next time I change the oil, I’ll try to use the drain plugs just to make sure I get all of the old oil out. I’ve been using a topsider to suck the oil out of the dipsticks.
Unfortunately, I couldn’t get the engine to start. I had also changed out the fuel filters and cleaned out the fuel tank. I’m hoping it’s a battery /air in the system issue. She cranks, but doesn’t fire. It’s been months since I’ve had the motor running. Not satisfying to do all that work and not hear the motor thumping away. Maybe tomorrow.

[mgphl52]

Do you any sort of extra primer pump? KAYLA has a bulb, like used on outboards. I always squeeze it till stiff before trying to start. With changing fuel filters you probably need to bleed the injection lines. When I'm being lazy, I do this by opening the compression release and spinning the starter with max throttle. That also helps a lot in colder weather!

[JD-MDR]

When ever I change fuel filters I fill the canisters as much as I can before screwing them on then I pump the air out with the mechanical pump lever on the fuel pump, in the right order. The racor filters first then the one on the engine. I rarely need to bleed the injectors. sometimes I do them anyway. My engine always fires right up. Thats when I bleed the injectors, after it starts.

[mgphl52]

Thats when I bleed the injectors, after it starts.

Once the engine has started why would you need to bleed the injectors???

[JD-MDR]

Just to be sure and to hear how the cylinders are firing. It doesn't hurt anything.

[Keith]

Back to the original thread. There are three separate oil compartments all with dip sticks.

1. the engine crankcase
2. the transmission, the transmission has forward, reverse and of course neutral. not sure what is being referred to as reverse gear.
3. the v-drive

Like on a car or truck the the transmission and v-drive oil does not need to be changed at the same frequency as the crankcase oil. Just check for clarity and top up/change as needed.


On the fuel filter changes. I have never needed to bleed the high pressure pump or injectors when doing filter changes. Just be diligent bleeding the air out at the racor and engine mounted filters.

Keith

[S/V Ethan Grey]

My new best friend is the decompression lever. I had no idea what that thing did. I went out to the boat, bled the engine fuel filter and cranked it again with the decompression lever engaged. I flipped the lever over and presto bango, she fired right up. Maybe air, maybe weak battery, who knows. But once she fired, she purred away. Rather than temp the fates, I decided to leave on a happy note and go home.

And thanks everyone for the info on the oil change. I keep referring to a reverse gear because that’s what the workshop manual calls it...those crazy Swedes.

So glad summer is over and 2nd spring is here in Florida

[Keith]

Those Crazy Swedes made one hell of an engine!!! Still kicking after 41 years with raw water cooling in salt water. The good news is it will run forever, the bad news is it will run forever. Each year I contemplate replacing it. Will this winter will be the year???

[S/V Ethan Grey]

Agreed! I hope to never replace mine. We’ll see. So far she sounds and seems to run great. I think there is something cool about trying to keep a 40 year old engine running. What I need to start doing though is rust protection on the outside. I guess I’ll start a new thread to discuss how everyone does it.

Those Crazy Swedes made one hell of an engine!!! Still kicking after 41 years with raw water cooling in salt water. The good news is it will run forever, the bad news is it will run forever. Each year I contemplate replacing it. Will this winter will be the year???

[Keith]

I bought a can of green rustolium that matched pretty close. Used a wire brush, wire wheel on my drill, a screw driver (for hard to get inside corners), vacuum and some newspaper for masking. It doesn't get much easier than that. Did it 3 yrs ago and it just needs a little touch up now.

Keith

[kerrydeare]

Agreed! I hope to never replace mine. We’ll see. So far she sounds and seems to run great. I think there is something cool about trying to keep a 40 year old engine running. What I need to start doing though is rust protection on the outside. I guess I’ll start a new thread to discuss how everyone does it.

Those Crazy Swedes made one hell of an engine!!! Still kicking after 41 years with raw water cooling in salt water. The good news is it will run forever, the bad news is it will run forever. Each year I contemplate replacing it. Will this winter will be the year???

I am not so sure that the exterior is going to be the ultimate issue. I ran my MD7A for 14 years or so almost entirely in salt water, and since the engine used raw water cooling I eventually found that I could not keep it going forever in such circumstances. Instead of adding FWC and so on, I decided to dump the original MD7A FWC engine and replace it wit a Volvo FWC job (Volvo 2002). No regrets, and that box ran well for some 26 or so years offshore.

I seem to recall that when I discussed the MD7A situation and problems with "The Swedes" in person at a boat show they pointed out that in Sweden the water is cooler and the salt water influence was less a problem (please believe I am not making this up). When I pointed out that I did not live in Sweden but did indeed live in New Jersey, the discussion proceeded no further.