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Flush Honda 15 HP

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Albanker
1st Mate

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USA
40 Posts

Initially Posted - 08/09/2013 : 16:43:11

I have a 2002 250 WK with a 15 HP Honda transom mounted . I recently bought the boat and it was a fresh water boat. Elsewhere in the forum I have seen instructions for making a flushing kit inside the head of the motor and attaching a hose. Can I tilt the motor and just run water through the hose to flush the or, even better, can I just leave the motor upright and run water through the hose?

Edited by - on

britinusa
Web Editor

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USA
5404 Posts

Response Posted - 08/09/2013 : 16:57:03

Welcome to the Association Al, (nice Burgee

)

Not sure it would be effective without the engine running. On our Nissan 9.8hp, I just attach the hose to the adapter in the shaft cover and run the engine for 10 minutes and then disconnect the the fuel line from the tank and let the engine run dry. We do that when the boat is on the trailer in our back yard.

Paul

Edited by - on

Stinkpotter
Master Marine Consultant

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Djibouti
9087 Posts

Response Posted - 08/09/2013 : 19:28:21

Follow the instructions.

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Albanker
1st Mate

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Response Posted - 08/10/2013 : 14:57:46

I was referring to the posts re modifications on this site . The reason for the question is that the instructions stop at installation of the flush kit. Hope someone understands my question above?
Thanks

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Stinkpotter
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Djibouti
9087 Posts

Response Posted - 08/10/2013 : 15:11:38

Sorry if I sounded abrupt, but these things vary by make, model, and method. Hondas I'm familiar with can be flushed from the fitting on the engine, but the engine must not be running--maybe because the water pump would be dry. Vertical is generally recommended. If your owner's manual is not sufficiently detailed, check [url="http://forums.iboats.com/honda-tohatsu-nissan-outboards-29/"]this engine forum[/url]. They have some mechanics who sometimes answer these questions.

Edited by - Stinkpotter on 08/10/2013 15:14:26

Tradewind
Admiral

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USA
531 Posts

Response Posted - 08/10/2013 : 18:01:45

I've always flushed my Honda in the horizontal position. A recent article on flushing in the BOATUS magazine said it should be vertical but my Honda manual doesn't specify. If it was vertical then the bottom end would be in the salt water, though the fresh water under pressure should keep the salt water out. Maybe I'll try it vertical next time and see how that works.

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JohnP
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1520 Posts

Response Posted - 08/13/2013 : 05:13:12

I have a Honda 9.9 which is essentially the same motor as the 15. The Honda Marine flush adaptors are specific for each of 3 size categories of Honda outboard. The top one shown on [url="http://marine.honda.com/outboards/accessories/flush-kits"]this site[/url] is suitable for both a BF15D and a BFP15D series motor. I ordered this same part from my local Honda motorcycle/outboard/PWC shop for my 9.9.

Since you are likely to have an integral flush port on the [port] side of the motor, under the cover, you can screw this adaptor into that threaded opening and connect a garden hose to it. Since I do this manoever sitting on the dock and leaning over the water, I have tied a wrist string to the adaptor to keep it from Davy Jones locker.

I flush the outboard, while it runs out of gas for about 2 minutes, with the fuel line disconnected, in the vertical position, out of the water, with enough water pressure to have water flowing out of all of the intake ports on the lower unit and to have a strong stream out of the telltale. When the engine is hot, the thermostat is open and allows flow through all the parts of the cooling system.

Since I've flushed the salt water out of the engine each time after use for the last 4 years, I have had no problems with impeller failure, as opposed to the 3 previous annual replacements in the shop. It's such a relief to have the outboard motor function 100% reliably and start on the first pull each time, often after weeks of sitting unused!

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Stinkpotter
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Djibouti
9087 Posts

Response Posted - 08/13/2013 : 05:52:39

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by JohnP
 I have a Honda 9.9 which is essentially the same motor as the 15...
<hr height="1" noshade id="quote"></blockquote id="quote">That depends on the vintages. In 2002 (I presume Al's vintage), the new (rounded cowl) 8 and 9.9 were the same engine, while the 15 was a 1990s model with a rectangular cowl. In the '90s, the 9.9 and 15 were the same, and the 8 was smaller. Starting around 2012, the 15 and 20 became the same.

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Sloop Smitten
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1181 Posts

Response Posted - 08/13/2013 : 12:20:28

The flush modification mentioned on this forum for the Honda 8HP requires access to rubber hoses to install a hose adapter. I don't believe the 15HP has these hoses and the cooling channels are all internal. You can visually verify if you have hoses but I think someone on this forum was unable to do the mod on his Honda 9.9 based on no hoses available to tap into. You might try searching the archived threads for additional information. I think JohnP has the right idea aabout using the available flush port to utilize a hose adapter. And Dave is right about following the directions for your outboard as to whether to run the engine while flushing or not. You do not want to burn up your impeller by running it dry while flushing above the impeller.

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piseas
Former Treasurer

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USA
2017 Posts

Response Posted - 08/13/2013 : 13:38:36

Welcome New Member Al! I have a 8HP Honda outboard and my Honda authorized dealer says I don't need to have the engine on while flushing. That is what I have done for 6 years and never had any issues in that matter.
However the manual says differently:

Cleaning and Flushing With the Optional Flush Kit
1. Wash the outside of the outboard motor with clean, fresh water.
2. Attach a hose from a fresh water faucet to the water hose connector of the
flush kit.
3. Remove the propeller (see page 58), and clip the flush kit rubber fitting over
the water inlet screen as shown.
4. Turn on the fresh water supply to the hose.
5. Start the engine and run in neutral for 10 minutes.

There is also controversy about changing car oil every 3,000 miles vs 5,000. I don't see anything inherently wrong with way. This method of flushing certainly beats putting on ear muffs.

An option is the following:
Cleaning and Flushing Without the Flush Kit
1. Wash the outside of the outboard motor with clean, fresh water to remove
mud, salt, sea weed, etc.
2. Remove the propeller.
3. Stand the motor in a suitable container of water. The water level must be
at least 2 inches above the antiventilation plate.
4. Start the engine and run slowly for at least 10 minutes

Steve A

Edited by - on

Sloop Smitten
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Response Posted - 08/13/2013 : 15:36:38

The reason Honda recommends running the 8HP engine while flushing is to allow the thermostat to come to temperature and open. If you have ever replaced the thermostat on a Honda 8hp salt water engine you will find the greatest accumulation of salt buildup around the thermostat as it is usually the smallest gap the water has to flow through. If the thermostat on the 8HP does not open you will only be flushing one side of the cooling system. On other models they may have a sufficeint bypass to allow flushing with the thermostat closed but that is just conjecture on my part.

Edited by - on

Tradewind
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Response Posted - 08/30/2013 : 18:13:54

Just checked my manual, 2006 Honda 8, using the garden hose adaptor, manual says "Do not run engine", nothing mentioned about the position of the engine.

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TakeFive
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Response Posted - 08/30/2013 : 18:52:33

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by Tradewind
 Just checked my manual, 2006 Honda 8, using the garden hose adaptor, manual says "Do not run engine", nothing mentioned about the position of the engine.
<hr height="1" noshade id="quote"></blockquote id="quote">
I don't get it. [url="http://cdn.powerequipment.honda.com/marine/pdf/manuals/31881804.pdf"]Here is the 2006 manual[/url] for the BF8A.

On page 46 it says:
<blockquote id="quote">quote:<hr height="1" noshade id="quote">Cleaning and Flushing With the Flush Kit
1. Wash the outside of the outboard motor with clean, fresh water.
2. Flush the cooling system, using the Honda flush kit (optional).
a. Attach a hose from a fresh water faucet to the water hose connector of
the flush kit.
b. Remove the propeller, and clip the flush kit rubber fitting over the water
intake as shown.
c. Turn on the fresh water supply to the hose.
d. Start the engine and run in neutral for 10 minutes.<hr height="1" noshade id="quote"></blockquote id="quote">
Searching the manual for "do not run" brings up two hits that refer to not running the motor when there are obstacles or people near the prop.

Personally, I would not advise flushing without the motor on for two reasons:

1) Motor must be warmed up for the thermostat to open up enough for the flush water to reach all the surface area
2) Applying water pressure from the hose can invert the impeller blades, leading to excessive flexing and possible cracking of the impeller.

Edited by - TakeFive on 08/30/2013 18:55:32

Tradewind
Admiral

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531 Posts

Response Posted - 08/30/2013 : 19:49:21

Rick,
May be the model difference, mine is an BF8D, tiller steering with electric start. Page 87 under "Flushing with the Honda Garden Hose Adapter", it says to

1) unlatch and remove the cover
2) attach garden hose to adapter
3) turn on water and verify good pressure
4) flush 10 minutes

Do not run Engine
After flushing remove garden hose and reinstall cover.

After reading your post of 8/13 I became concerned about the way I've been flushing the engine, today was the first opportunity to get to the boat and check the manual.

Your reasons for flushing with the engine running make sense but my boat stays in the water and to flush with the motor running the bottom end would be in the salt water which would defeat the flushing with fresh water.

I can only assume the difference is the models of our engines, BF8A vs BF8D, though I don't know what the actual differences are.

http://cdn.powerequipment.honda.com/marine/pdf/manuals/31ZY0608.pdf under STORAGE.

Edited by - Tradewind on 08/30/2013 19:56:19

Stinkpotter
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Djibouti
9087 Posts

Response Posted - 08/31/2013 : 08:16:25

The BF8A and BF8D are completely different outboards. (I've had both.) <s>The A (or "Classic", with the squared-off cowling) takes a brass fitting that screws into a port on the side of the engine block, while the D (newer, rounded cowling, with optional electric start and high-thrust prop) has a connected hose inside the cowling that you unscrew and connect to a garden hose.</s> Either way, the flush process likely leaves the water pump, which is in the lower unit, essentially dry, which if the engine is running, will likely destroy the impeller. You find out about that when you run the engine in water, it overheats, and sends pieces of the impeller throughout the cooling channels--or so I've been told.

If you use earmuffs or another method of getting water into the intake below the water pump, then the engine can and probably should be running, with the advantage (as mentioned) of the thermostat being open during the flush.

Most mechanics only use the latter method (muffs) or a water tank, because it's universal. Unless the mechanic is Honda-certified, I wouldn't take his advice over what the manual says, at least not without some discussion.

Edited by - Stinkpotter on 08/31/2013 09:25:29

TakeFive
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Response Posted - 08/31/2013 : 08:57:44

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by Stinkpotter
 The BF8A and BF8D are completely different outboards...
<hr height="1" noshade id="quote"></blockquote id="quote">
Agreed, and I did not realize that he had the BF8D instead of the BF8A.
<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by Stinkpotter
 ...The A (or "Classic", with the squared-off cowling) takes a brass fitting that screws into a port on the side of the engine block...<hr height="1" noshade id="quote"></blockquote id="quote">
Not from what I have seen. The 2006 manual that I linked above for the BF8A shows a fitting that attaches under the antiventilation plate. Perhaps you're thinking of the BF9.9A/BF15A clones. And even for the BF9.9A/BF15A (which I have), the connection port is just above the lower unit, not on the engine block.

FWIW, this attachment point under the ventilation plate is also below the water pump, so I can't imagine that the pump would run dry since it's right between the hose connector and the motor that it's cooling. I can't see how water could get to the motor without going through the water pump.

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by Stinkpotter
 ...Either way, the flush process likely leaves the water pump, which is in the lower unit, essentially dry, which if the engine is running, will likely destroy the impeller...<hr height="1" noshade id="quote"></blockquote id="quote">
I agree that this is correct when the flush port is located in the top of the motor under the cowling, which would seem to be why Honda does not recommend running the motor for the BF8D. But not true for attachments points on the lower unit, which is why Honda's manual recommends running the motor for BF8A and BF9.9A/BF15A.

I agree that any DIY work should follow the manual's recommendation. But if your manual says to run the motor, you can expect to do so safely without destroying your impeller.

Edited by - TakeFive on 08/31/2013 09:12:04

Stinkpotter
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Djibouti
9087 Posts

Response Posted - 08/31/2013 : 09:22:18

Ya, I think I've confused the two, both of which I've owned. The new models (D) have the brass adapter that screws into the block. The hose that unscrews at inside the cowling is on larger models. The real lesson here is follow the directions, which are model-specific (not just brand-specific or even size-specific). Don't listen to confused people like me!

Edited by - Stinkpotter on 08/31/2013 09:24:31

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