Need help understanding MD7A fuel lines

[TrentePieds]

Originally Posted by esarratt

Huh?
Or are you referencing the clamps on the engine heater/fuel lines?




Yeah, I'm going to give her a try and see how many years she'll give me.

No joke. A sincere compliment. Wood, species properly chosen, is in many applications superior to metal. Many things, normally made from metal these days, were made of wood in the "old days", and the ship's carpenter could whittle them in his lap using simple hand tools.

"Seeing how long she'll last" is sound policy, PROVIDED you have a plan for what to do when she croaks when you are in a tough spot. Have your alternative installation ready and with you, along with the tools required to make the repair.

TrentePieds

[farm sail]

Agree with a64pilot looks like the return line is routed back to the fuel feed line right before s quick connect for a portable outboard fuel tank

[esarratt]

Originally Posted by TrentePieds

No joke. A sincere compliment. Wood, species properly chosen, is in many applications superior to metal. Many things, normally made from metal these days, were made of wood in the "old days", and the ship's carpenter could whittle them in his lap using simple hand tools.

Got it. Thanks.

[Shawn67]

While you are working on it pull the exhaust manifold off and clean it out. They clog up on the MD7A and cause overheating. Mine was completely clogged so no water was flowing through the engine. Also check the water pump on the rear of the engine to make sure it isn't leaking.

Have you started working on the engine or is that how you received it in the boat? If that is how you received it you are missing your alternator, the throttle and fuel cutoff cables look like they not connected and the air cleaner and PCV are not there.

[esarratt]

Originally Posted by Shawn67

While you are working on it pull the exhaust manifold off and clean it out.

Oooooo. Good idea! That is easy since I am back there anyway doing so much work.

Originally Posted by Shawn67

They clog up on the MD7A and cause overheating. Mine was completely clogged so no water was flowing through the engine.

Yep, I already sucked out a piece of rusted metal with the vacuum cleaner when I was fixing a bent water muffler exhaust intake. Volvo said the part was not available and if it was...$100. I took it to a machine shop and they bent it back in place for $10. By the way, the pipe is actually copper. I was quite surprised.

Originally Posted by Shawn67

Have you started working on the engine or is that how you received it in the boat? If that is how you received it you are missing your alternator, the throttle and fuel cutoff cables look like they not connected and the air cleaner and PCV are not there.

Yes and yes. When I got the boat the alternator was off; after setting the boat on the hard the PO had taken the alternator off for repairs then got busy with other life-work. It is an old Marchal alternator that was not charging.

The local repair shop was unable to obtain any parts with which to rebuild the alternator because of its age; they also could not test it because they do automotive primarily and did not have the equipment.

We scavenged the pulley and re-drilled the hole to fit an AC Delco post. The alternator I bought is marine grade ($350), with spark arrestors and is normally used on a Mercruiser.

Joe (Suffolk Alternator & Starter Service in Suffolk, VA) said the Merc would be easy to find parts for. He also changed the regulator (?) inside so it would charge quicker (without revving the engine). He took good care of me.

The throttle cable was lying in water in the bottom of the boat; it is busted and needs to be replaced (after the alternator). I have taken off the air filter to clean it and will buy fuel cables next week after alternator repairs.

FWIW: I have the old Sev Marchal alternator (part# 70 229712) if anyone needs it. You pay for shipping (just my exact cost) and it is yours. I do not know if it works, but if you need it for parts you can have it. It was apparently working, just not charging well, when removed from the boat. There is no pulley on the alternator anymore. I can send you pics if you PM me.

[Shawn67]

" when I was fixing a bent water muffler exhaust intake. Volvo said the part was not available and if it was...$100. I took it to a machine shop and they bent it back in place for $10."

Is that on the water injection point? On my Sabre they didn't use the Volvo part for that. They made a riser out of black pipe. I replaced that when I was converting to fresh water cooling. The flange on the exhaust manifold is just 1.25" NPT.



If you are removing the exhaust manifold you are going to need cooling system gaskets. West Marine sells them cheaper than Volvo. Order part #10511004. I know they say it is for stern drives but it is the proper set for the MD7A. That has the thermostat gasket, the O ring in the thermostat housing as well as the square ring push on gaskets for the thermostat housing, exhaust manifold inlet the two at the water pump and the gasket for the connection to the transmission.

If you want to make another handy change consider swapping out that hard pipe from the transmission to the water pump. It is a PITA to get back together (or at least it is in the Sabre due to access) and the threads in the brass flange are easily damaged. Mine was slightly damaged and tended to suck air which reduced the pumps efficiency. The flange on the transmission unscrews and it is 1/2" NPT into the transmission. I cut the pipe a couple of inches below the water pump and its exterior is 1/2". With brass pipe I built a new connection from the transmission to the water pump and use a small piece of 1/2" ID hose to connect the two.





Sounds like you have a nice alternator setup. I will have to keep that in mind if mine ever dies.

Shawn

[gjordan]

Shawn, your new piping looks great, but I am wondering if brass (rather than bronze) will de-zinktify (sp?) in short order? Brass and salt water usually dont go very well together. Just wondering? _____Grant.

[Shawn67]

Thanks, I am happy with how that turned out as it removed the troublesome original connector. I actually ended up putting a T out of the tranny and a ball valve (on the aft side) with the other side of the ball valve sealed with a screw in plug. That lets me partially drain the system by unscrewing the plug, screwing in a tap (connecting a drain hose) and opening the ball valve.

Good point about brass and salt water. In my case I used brass as it was available locally and that pipe no longer has salt water in it. That is part of the fresh water cooling loop now.



That one is before I secured all the new hoses.

There is still brass in the raw water circuit though. The heat exchanger is brass (with a zinc) and I had to use thick wall brass BSPT to hose barb adapters on the piggyback raw water pump. I couldn't find those adapters in bronze.

Shawn

[gjordan]

Shawn, I really like the idea of using the fresh water side to cool the tranny. I am slowly rebuilding my MD7A that has fresh water cooling, but the raw water still runs through the transmission. I have heard of a few Volvo transmissions being ruined from the cooling passage rusting through. Fresh water and coolant would make it last years longer. I will see if I can make a plumbing system that seems practical. I just looked at your 2nd photo, and it appears that you have a major kink in the lower hose. It might just be the photo, but if it is kinked n, it will cause circulation problems. I think it is a very good idea. Grant.

[Shawn67]

When I took that flange off the tranny I also pulled out a large chunk of rusted metal that was sitting behind it. I've read of several MD7As that were pulled out of service because the transmission water jacket rusted out. Using fresh water/coolant there should help reduce the rusting in the cooling jacket on the transmission. Flip side is the tranny is likely running a little hotter due to the increase temp of the coolant flowing through it.

On your engine do you have the fresh water pump on the front of the engine? In my setup the original raw water pump became the fresh water pump and an add on pump (Johnson 10-24143-1 replaces the original water pump cover) became the raw water pump. That made the plumbing much easier for my conversion.

Raw water side is from the seacock -> strainer -> add on pump -> heat exchanger ->exhaust.

The fresh water side is heat exchanger -> tranny -> fresh water pump -> exhaust manifold/thermostat housing as stock -> out thermostat housing to the heat exchanger.

That picture was before all the hoses were installed. The raw water feed isn't connected to the heat exchanger for example. That hose (raw water out of the heat exchanger) looks kinked in that picture but it is a wider radius curve than it appears. I get very good flow out the exhaust and the engine cooling is working well.



Spot 1 is raw water intake to strainer
Spot 2 is from raw water pump to heat exchanger
Spot 3 raw water from heat exchanger to exhaust
Spot 4 fresh water from thermostat housing at heat exchanger
Spot 5 fresh water output from heat exchanger to tranny inlet

Shawn

[Wotname]

Originally Posted by esarratt

Yeah, there is an old and very dirty metal tank with the boat that will be showing up on the forums soon with my questions.
…………...

I just came across this link about small marine diesel fuel systems and thought you may be interested. Try to ignore the Yanmar reference

FUEL SYSTEM INSTALLATION

[Wotname]

Originally Posted by boeing1

Wotname,
very nice installation....

Thanks, all my own work and it has been in service 7 years now (but only 280 hours).

[hpeer]

While you have the exhaust manifold off look at the fuel return FITTING. on my MD7A it had an origional fitting where the hose could not be changed without removing the exhaust manifold.

There is a banjo fitting and a crimped retainer. I cut off the retainer (with a Dremel cut off wheel) and made that a normal hose clamp fitting. If the hose goes I can easily replace it.

Same goes for the hose to the lift pump.

[hpeer]

Shawn, your work embarrasses me.

Good going.

[Wotname]

^^ me too