volvo penta md 7a exhaust water flow stopped

Engines, Drive trains, Propellers, Steering, Ground Tackle and other mechanical system
User avatar
VeloFellow
Posts: 129
Joined: Tue Dec 24, 2013 9:41 pm

volvo penta md 7a exhaust water flow stopped

Post by VeloFellow »

This weekend we met our highest winds yet. 60mph gusts, 45mph thunderstorrm. Coast guard warning prepare for storm, seek shelter. at five mph that wasn't going to happen. . We heard the Coast Guard answering madays. Launching helicopters and vessels. But Clave' was fine. A couple kayakers rescued. a few power boats towed.
After dropping sail started motor. Wind more power than motor. Wind on the beam we were 45 degrees bare poles. But I didn't stay in that orientation. Raised sail shut down motor when wind subsided. Motored around St Pete Municipal transient dock but no place in the end. Found a quiet corner. Morning calm, motor ran fine heading out of the basin with stops for fuel and pump out. When I restarted for safety back up while crossing the shipping channel an hour later, we noted a different sound of engine and no water flow out the exhaust. Shut down as crossed the channel and sailed to our dock.
My thoughts:
Possible air ingestion? I would have thought earlier issue after the motor sailing at extreme heel. Ran for hour after the storm and 15 min entering harbor and exiting harbor with stop for refuel and pump out.
Failed Impeller?
Fouled intake or sea water filter?
Other?

What is your approach to this on the water?

I have sailed dinghies and catamarans and ride a bike. I wisely crewed on all the big boats I sailed on. Owner and paid hands handled the mechanicals.
The mechanical stuff toilets, electrical systems, engine/fuel and exhaust are all new to me. So you cant offend me by the simplest approach possible.
(my brother has lots of boat experience and is going to walk me through his approach next time I am getting ready to head out again.)

Clave' after the storm. Nothing happened. Pictures don't lie.
Attachments
clave' st pete small.jpg
clave' st pete small.jpg (82.07 KiB) Viewed 9104 times
Mike
s/v Clave'
1981Freedom 28 #112
Currently sailing Tampa Bay
Buit by Fairways Marine Hamble England
cat ketch, centerboard , wishbone booms, tides track slides
yanmar 2ym15 2blade prop

User avatar
GeoffSchultz
Posts: 1135
Joined: Thu Dec 04, 2008 8:39 am
Location: BlueJacket: Guatemala
Contact:

Re: volvo penta md 7a exhaust water flow stopped

Post by GeoffSchultz »

All of the above is possible. Open up the raw water filter to see if you're getting water through the thru-hull and/or if the filter is clogged. If water is flowing, then you need to check/replace the impeller. When was the last time that it was replaced?

-- Geoff
BlueJacket
1997 Freedom 40/40
http://www.GeoffSchultz.org

ericsmith3d
Posts: 12
Joined: Thu Dec 04, 2008 5:25 pm

Re: volvo penta md 7a exhaust water flow stopped

Post by ericsmith3d »

Geoff's right. Start at one end and work your way to the other. Starting at the intake end was easiest for me (also the likeliest, ie forgetting to open the thru hull). The only time I had her overheat was leaving Elizabeth City about halfway to the Ablemarle. I opened the strainer, no water flow. Took out the basket and found an eel that had either swam up the intake and gotten stuck or had been sucked in. Took about twenty minutes to get it out

User avatar
VeloFellow
Posts: 129
Joined: Tue Dec 24, 2013 9:41 pm

Re: volvo penta md 7a exhaust water flow stopped

Post by VeloFellow »

Thanks,

My brother had given me a similar outline over the phone. Having the flow fail when it did was easy. It was a nice sailing day. The evening before would have been more stressful. We were constrained by land and bridge on three sides and the shipping channel along the other. Lots of shallow water to our lee.

I have had Clave' since December. Not sure when impeller last changed. I do have a spare impeller in the parts kit. We keep the boat 250 miles from my home. I have just enjoyed sailing it when I have gone down. I am fortunate my brother has done essential maintenance.
Mike
s/v Clave'
1981Freedom 28 #112
Currently sailing Tampa Bay
Buit by Fairways Marine Hamble England
cat ketch, centerboard , wishbone booms, tides track slides
yanmar 2ym15 2blade prop

User avatar
Castaway
Posts: 286
Joined: Sat Dec 13, 2008 8:40 pm
Location: Lerwick, Shetland Isles

Re: volvo penta md 7a exhaust water flow stopped

Post by Castaway »

If you were heeled so much, you could easily have had the intake out of the water, so air will have been sucked in, which would prevent the pump being able to draw water through the siphon loop, leading to running dry. Close the seacock, open the filter, fill with water if dry, close filter then change impeller (always a good idea, even if only run dry for a few minutes), open seacock and try starting again. If water comes through, then problem solved, otherwise more thorough dismantling/diagnostic required.

Often helpful to coat the impeller in liquid soap after fitting, since this will let it run dry for a few minutes without damage, whilst water gets sucked through. If the above doesn't work, it's probably time for the mechanic to visit!

This summer, I had a blockage in the gear box cooling system (Volvo Penta), only discovered after significant surgery.

Good luck.
Gerald Freshwater,
s/y 'Castaway', (UK F35 cat ketch, centreboard, 1987)
Lerwick Boating Club
Shetland Isles, Scotland

User avatar
VeloFellow
Posts: 129
Joined: Tue Dec 24, 2013 9:41 pm

Re: volvo penta md 7a exhaust water flow stopped

Post by VeloFellow »

The problem with having a boat 250 miles away is lots of the weekend is driving...
And when it is a repair weekend...I wanted to sail...That is why I have a SAIL boat.

I told my wife I am going to get some 16' sweeps and oar locks. I don't really care about the engine...Lets see, the engine can barely get us in some of the passes against the current, my sweeps???

So the testing. I have a Volvo Penta md7a in a boat built in Hamble England in 1981.

I checked underwater, no simple plug of the intake
Removed the hose from the seacock filter to the top of the impeller housing and lowered it and the water flowed in.
I removed the cover from the impeller housing and the impeller. No water. but out comes coolant?
The impeller looks normal but maybe one wing has a little curve? The ends of the impeller have little corner nicks from the plate foot...but not significant?
Restart with new impeller. dry...

A diesel mechanic friend of my brother suggested the seals on the coolant pump probably need to be replaced and their wear may be the reason sea water impeller not priming and getting flow....I ran out of time. more parts. Elco?

Got a few of the other repair task done. Watched one of my brothers grandsons who just fininshed his first sail camp perform in an optimist dingy in a gusty prefront wind. What sailing is.
Mike
s/v Clave'
1981Freedom 28 #112
Currently sailing Tampa Bay
Buit by Fairways Marine Hamble England
cat ketch, centerboard , wishbone booms, tides track slides
yanmar 2ym15 2blade prop

AlanK
Posts: 127
Joined: Wed Dec 10, 2008 6:59 pm
Location: Freedom 33 Boston, MA USA

Re: volvo penta md 7a exhaust water flow stopped

Post by AlanK »

Probably this won't help. But one year when I was starting up my engine for the first time of the season (its a yanmar but the seawater side is a standard jabsco pump with impeller) there was no seawater flow. I checked everything with no luck. I finally disconnected one of the hoses to the pump and squirted/poured in some water. Surprisingly this solved the problem. These are supposed to be self priming but apparently not always. I've never had this problem again just that one time. Just FYI.

rds
Posts: 50
Joined: Mon Jul 06, 2009 9:32 pm

Re: volvo penta md 7a exhaust water flow stopped

Post by rds »

My boat has raw water cooling circuit with two U-shaped loops (before mixing elbow and after muffler ). The first loop goes from seacock ,via strainer, about 10 inches above water line (to prevent engine flooding), via raw water pump (below waterline) ,via main heat exhanger and oil cooler and into exhaust mixing elbow. It has a vacuum breaking valve in it, so it might be possible that this valve has stuck in opened position and therefore prevents self priming action of the pump ? it is not difficult to check it.The valve is plastic and is screwed into plastic U elbow (in my case ). It is supposed to be closed when water is flowing and gets opened to prevent siphoning of water into muffler and potentially flood the engine when it stops.

P.S. just found MD7A the detailed view online
http://www.marinepartseurope.com/en/vol ... 3636C.aspx
comes out this is raw water cooled diesel. According to this diagram it also has vacuum valve ( item# 59)
and also got thermostat ( # 6 ) which might be stuck in closed position

User avatar
VeloFellow
Posts: 129
Joined: Tue Dec 24, 2013 9:41 pm

Re: volvo penta md 7a exhaust water flow stopped

Post by VeloFellow »

Thanks for all the suggestions. I am 250miles from my boat so wont get back to it for a few weeks.

My brother is a great help, but has a life, a wife grand children he is teaching how to sail and several jobs besides being onsite foreman of the Rebirth program of a very used F28. He talked to his diesel mechanic who thinks it cant get suction because the seals on the coolant side of the impeller axle are leaking. This makes sense and might explain why coolant I wasn't expecting came out of the impeller housing, which has inflow and outflow water lines,when I opened it and pulled out the impeller and shaft.

In this diagram you can see parts labelled 13 from the same source rds pointed out. I have never seen cut aways or photos that exactly match my engine. It was the hamble scramble md7a. http://www.marinepartseurope.com/en/vol ... 13639.aspx

I had planned to take pictures and have tea while I was working in the engine room, but spent far too long searching the bilge for the impeller housing cover which slide off the "flat" exhaust and...hid among the bildge rats. And I don't know where they would set up the cameras and put the sound crew. I do see an advantage to little grand children;-) Just hard to get much work out of them before they turn in to teens or adults...
Mike
s/v Clave'
1981Freedom 28 #112
Currently sailing Tampa Bay
Buit by Fairways Marine Hamble England
cat ketch, centerboard , wishbone booms, tides track slides
yanmar 2ym15 2blade prop

User avatar
Castaway
Posts: 286
Joined: Sat Dec 13, 2008 8:40 pm
Location: Lerwick, Shetland Isles

Re: volvo penta md 7a exhaust water flow stopped

Post by Castaway »

I've just replaced the seals on my Volvo (type 2003) water pump, not quite the same as yours, but not a difficult job. The seals are less than £10 each - best to replace both – and slide on easily with a smear of engine oil on the shaft. If your pump is the same as the one in the picture, you don't even need to remove the bearings, if I remember rightly.

Smear the new impeller with liquid soap before assembly; it goes together better, and saves the impeller from damage due to running dry whilst you start up for the first time. Also, close the seacock, fill the water filter and seal the top, then open the seacock again just prior to starting, to maintain the syphonic loop. The syphon-breaker on the outlet side makes no difference to suction, although if it is damaged, it will leak when the engine runs.

Have fun!

By the way, where is your boat? Ours is presently in Shetland, where there is another, and there are at least two more in Scotland that I know about.
Gerald Freshwater,
s/y 'Castaway', (UK F35 cat ketch, centreboard, 1987)
Lerwick Boating Club
Shetland Isles, Scotland

Post Reply