MD7A raw water maintenance question - Barnacle Buster

[S/V Ethan Grey]

Wow that looks great. Now I wish I had taken my manifold off when i had the thermostat and water pump removed.

[Kickin Bears]

Took the manifold off and soaked it in muriatic acid and water 6-1 ratio for two 10 minute soaks also soaked the thermostat housing and the mixing elbow. It wasn’t as bad as I thought. I’ll put it togeather. t tomorrow. Luckily I had the gaskets. Cant figure out what the round mark. I mean the about 1” round mark between the two square exhast ports The gasket has a hole for a port but the manifold and the head are either completely plugged or they not anything??? I wish I would have ordered a manual.

+1 ... that’s cleaning up nicely!

Below is a pic from the owners manual for cooling water flow, and another pic from the workshop manual

Where did you get the gasket?

[JD-MDR]

Thanks “kicken bear”. I’ll look for the reciept when I get home. I think I got it online I googled md7a parts. Here is a photo of my old gasket and of the manifold. I think the mark from the round hole is just carbon buildup from the gasket. I dont think I have that port on my manifold. I tapped on it I feels solid. Maybe The gasket is also for another model

[JD-MDR]

I guess it was carbon. It’s so hard to chip out. I used s carbide drill bit around and chiceled. Im not gonna do any more. Im afraid of breaking the manifold. It will be a million times better. One photo is the head. Hard to acess kinda rough.

[JD-MDR]

I put it back together and thought I was gonna flush it with Barnuckle Buster but I cant get a good seal on the tubing where it t’s off halfway to the thermastat. I knew thete would be problems. Niw I will be disabled for a while I need advice or a good shop that can fix that hole or a different way to connect that pipe. And the pipe seems a little bent it doesn’t line up perfectly. Maybe I should look for a new manifold and water pipe. Im gonna take it to the Volvo mechanic at MarinaDelRey. There is a good one here but he’s too busy and dhort handed. I think

[JD-MDR]

Found the price of a new mAnifold looks like about $2000. Decided to give it one more try. I drilled and rheemed out that hole for the coolant pipe. I think I got it. Just finished flushing for sn hour with Barnickle Buster. I think it’s the same as muriatic acid. Smells the same Costs 16 x. I hope all is well. Ill try to button it up and start It tomorrow

[Kickin Bears]

Wow!! That carbon buildup is unreal; I bet that was a lot of work to grind out with a drill bit (and likely a very anxious experience ). Glad you were able to ream out the water pipe hole to get the fitting right.

I have to imagine this is going to give it a new lease on life. Look fw to hearing how she runs!

[JD-MDR]

Having trouble with the water pump. I guess I’m glad I got to look at the manifold. I didn’t clean it that good because I’m pretty sure I’ll be taking it off again soon. This should be good for a while. Next time I’ll take it to a machine shop. I have a feeling ill have to overhaul everything

[JD-MDR]

Funny thing is I thought this engine was running great. I saw the temp gauge fluctuating last week and after this conversation I just decided to take a look.I must of taken the pump in and out 7 or 8 times. couldn't figure out what the problem was. I even went and bought snap ring tool to take the pump apart and check the seal . Finally I figured out it was in backwards. There is no direction arrow. I think I had that problem before. I etched in a direction arrow. Seems to be working great now. I ran out of time though. Had to get home so I only ran it for a few minutes. It's good that I took the pump apart . The shaft was starting to show corrosion and the bearings were stiff. I wasn't able to access the head . So There is still some carbon there. Like I said earlier. I think I will be pulling this engine for an overhaul.

[JD-MDR]

https://www.youtube.com/watch?v=0G9m0sD5AmQI just watched a utube video Under coolant tube for md7a. He had the same blocked hole but he left it like that. I hope I didn't screw up by drilling it out. I ran the motor some more today and the coolant tube has a small drip at the t-off to the manifold, the one I was having trouble with. Maybe it will seal itself. I don't know what to do. I would have to pull the manifold again . I'm not gonna worry about it for a while.

[Kickin Bears]

Thx for posting that vid. That port has me stumped. So based on the manual pics above, the port is open on the block but closed on the manifold side (?)

That leads me to believe there’s some type of heat exchange / temp equalization intended in design, but totally guessing.

I’m very interested in this; I’ll call up some folks near me to try to get intel.

[JD-MDR]

Thank you. I wish I had someone here to ask. The mechanics are so busy Its almost impossible to get any info from them. It clearly shows it open on the head and the gasket has a hole also. While I was drilling it really felt like carbon. Definitely not steel. When I had it off I took it to the Marine Mechanic shop. I wanted them to clean it up but they didn't have time. I could have left it for who knows how long. He advised me to soak it in Muriatic acid myself. I asked about that port and he didn't know off hand. He didn't waste no time looking at it or looking it up. Funny how busy they all are even at the rates $100-150 per hr. The boatyards, the sail loft, everybody is swamped.

[JD-MDR]

[quote="Kickin Bears"] Thx for posting that vid. That port has me stumped. So based on the manual pics above, the port is open on the block but closed on the manifold side (?)
Where do you see it closed on the manifold side in the manual?

[Kickin Bears]

Thx for posting that vid. That port has me stumped. So based on the manual pics above, the port is open on the block but closed on the manifold side (?)
Where do you see it closed on the manifold side in the manual?

Those are the only two pics available re: the MD7A cooling system, pulled from both the owners manual and the workshop manual.

Don’t misunderstand what I wrote; that “(?)” was very intentional!!

I’m not convinced that’s the case, just trying to rationalize why it wouldn’t be open (with difficulty too)

[Kickin Bears]

Just wrapped up a 30m call with a Volvo Penta certified services mechanic, and he didn’t know. He said all the material he had available I already had (i.e. workshop and owners manual).

He suggested looking up the end of the manifold to see if a port led to that spot (vs over or by it). He said the material would look different if bored, but seemed stumped that it would be that tough

Any chance you have a fiber optic camera you can snake up there for some pics? I have one, they are great for seeing around and into tight spaces (plus the lamp); worth having one handy with today’s smart phone tech