Through Hull Position on a Perkins Engine

[Scott2]

Hi Everyone, I will now show my embarrassing ignorance. When I operate a Perkins Perama 103-06 on the 1994 Catalina 270 LE I just bought, do I open all the through hulls leading to the engine and run it with them open? Do I close them once the engine is started? Do I start it with them closed and then open them after the engine is started? I ask this because the owner is no longer available to answer my questions since he passed away :-( and the operations manual talks about the start sequence but is mute on what to do with through hulls.
Thanks in advance you for your answer.

 

[The Garbone]

Start the motor and then open the thru hull. You do not want to take water in until the engine is running because it can flow into the cylinders if you crank too long and she does not fire filling the muffler.

 

[zeehag]

they must be open when running. water needs to go thru engine. water will not go thru engine with thru hulls closed.
as for cranking water into engine, the only person i knew who regularly did that is now dead. his risers were too short. he was trying to save dough. oops
make sure your risers are tall enough to keep out water when cranking starter. that is what they are there to do. do not crank starter as you would a car. remember you are pumping water.
if you donot know what something is, take a pic and post it here or call a marine mechanic for about 105 usd hourly and gain his expertise as much as possible in that hour.

the only drawback to opening thru hulls AFTER starting engine is that when you forget to open em, your engine will suffer and you will pay out lotsa dough to rebuild it.

 

[The Garbone]

they must be open when running. water needs to go thru engine. water will not go thru engine with thru hulls closed.
as for cranking water into engine, the only person i knew who regularly did that is now dead. his risers were too short. he was trying to save dough. oops
make sure your risers are tall enough to keep out water when cranking starter. that is what they are there to do. do not crank starter as you would a car. remember you are pumping water.
if you donot know what something is, take a pic and post it here or call a marine mechanic for about 105 usd hourly and gain his expertise as much as possible in that hour.

the only drawback to opening thru hulls AFTER starting engine is that when you forget to open em, your engine will suffer and you will pay out lotsa dough to rebuild it.

You are assuming he has the proper riser, not knowing his boat I do not assume. Maybe the PO cobbled something screwy together after having a bad mixing elbow. We do not know.

Also because I sail a C30 and there is not enough space for a proper riser and this is the safe way to start for me. Just do not forget to open the thru hull.

 

[dziedzicmj]

There is no reason not to open the through hull before cranking the engine on a C270. It might be actually tricky to do it after it is started, as you have to go down the companionway, squeeze into the stern cabin and reach under the mattress to the through hull. In that time your water pump impeller is probably gone. I haven't heard of any issues with pumping water into the cylinders this way, unless you have some major problems with the start. The Perkins should start after about 2-3 s of cranking. Give it a little bit of throttle when starting.

 

[Scott2]

Took delivery today and she fired right up. I used the closed through hull method by disassembling the aft berth, mattress put up in the v-berth out of the way and doors open for a clear shot at the through-hull once the engine starts to sing that sweet three cylinder tune. As soon as the engine started I sprung into action, rushed below decks and opened the valve. Sounds like from the conversation I could have done it either way relatively safely and perhaps with a little less effort. Just out of curiosity, what happens when the cylinders get flooded (other than the engine doesn't start?) Any special maintenance required or just let them sit a while and drain out. Thanks for for your patience and teaching a newbie....

 

[dziedzicmj]

Engine water-locked
If you flood the engine cylinder(s) with water, the engine would water lock. It would not turn any more. If you do it when it is turning, major damage could (would) occur. Normally, you do it (well, you normally, don’t do it) when the engine is stationary or you are just cranking. Then the chances that you can get away with it are reasonable. You have to remove the water out. The easiest thing, in the Perkins, is to remove the glow plugs (you could remove the injectors, but this is much more involved). This opens all cylinders. You could try turning the engine (by hand), but I would recommend to use a hand pump (Pela) to remove as much water as you could first. Once all cylinders are empty, you can crank the engine using the starter. When you do it protect the glow plugs opening with a rag or two - the water will be shooting across the cabin and make a lot of mess on the starboard wall.

Since this kind of flooding occurs from behind (i.e. from the muffler/exhaust side) you should assume that the muffler and the exhaust hose are full of water. Remove water from there using the hand pump.

Once all of it is done, reassemble all parts, change the oil (potentially twice) and you should be good to go.

Of course, all of the above with fingers crossed all the time that nothing went wrong.

 

[PineyWoods]

Start the motor and then open the thru hull. You do not want to take water in until the engine is running because it can flow into the cylinders if you crank too long and she does not fire filling the muffler.

In 40 years of many sail boats with diesels, and cruises with two of the world's most compulsive motor cruisers on their boats, I've never heard of this caution - and certainly not in any cruising text book relating to engine management I've read. I can't imagine even with 10 sec. of continuous starter activation with fuel shut off that more than a few ounces will be pumped out by the water pump, and that the starter will burn out long before any but the most jack-legged installation without a water-lift muffler will flood the cylinders.

So when you shut the engine down at sea do you run down and close the intake? Do you have an exhaust shutoff valve also, as this is where all the floodings I've heard of come from?

Pete

 

[The Garbone]

Ah shucks Pete, now I feel silly. Hydrolock is indeed so uncommon they have yet to invent a name for it.

 

[Stu Jackson]

Start the motor and then open the thru hull. You do not want to take water in until the engine is running because it can flow into the cylinders if you crank too long and she does not fire filling the muffler.

NOT a good idea. You end up running the water pump impeller dry, with all the bad things that can happen with that.

My cockpit panel says 30 seconds max. You could get 5 starts in that amount of time.

The BS that comes up on some forums is truly staggering.

 

[The Garbone]

Funny thing. I bought a transmission that was pulled off an engine someone cranked a few times and it did not fire. Came back after checking things and probably having a sandwich and when he tried again he had water in the cylinders. Bet he was glad he relied on that anti siphon loop.

If 10 to 20 seconds of cavitation nukes your impeller yikes.

 

[kloudie1]

It is not the slow speed of cranking that will total the impeller, it is the time from the engine starting until the water gets to the pump.. and the backwards bending of the impeller vanes from too high a pressure differential across the pump.. at a warm-up speed of say 1000 rpm, each vane will have seen 500 backwards cycles in 30 seconds.. That will tear up an impeller!
Do Not start with the cooling water seacock closed unless someone is right there to open it immediately when it fires..

 

[bawlmer]

You should always open the through hull before starting the engine. It is very bad for your raw water pump impeller to run it dry for any period of time. I would forget that instruction as it can do much more harm than good. As for flooding your engine the manual says that if you crank your engine for more than 30 seconds you must stop cranking and drain your aqualift muffler. It is in the port side storage compartment under the mattress. The valve to drain it is on the bottom of the back side of the muffler. As long as you follow this practice you should be OK. I have a Westerbeke so I can't help you with the Perkins but I am sure the exhaust is the same. I have had a 270 for 3 years and I think (hope) I have figured out most of its idiosyncrasies. PM me if you need more info about the muffler. I just had it apart after replacing the mixer elbow.

 

[Scott2]

Thanks to all those who replied. I appreciate your help very much.

Scott