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Honda 8hp cooling question

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pfduffy
Captain

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USA
317 Posts

Initially Posted - 06/06/2011 : 08:52:19

I have an older Honda BF8A (square cover, not rounded) and I ran it yesterday in a test tank. My question is how much water should be coming from the outlet? It seems to flow steady for a while and then less so as the motor gets warmer. When I notice that the stream is reducing, if I cover the outlet hole with my finger for a couple of seconds, it seems that the stream improves for a little while - almost like the blocking the outlet primes the pump.

Note - when the throttle is open a bit, the stream from the outlet hole seems to increase.

The water pump has 2 or 3 seasons on it of reasonably limited use (less than once a week - unfortunately, I don't monitor hours.)

Pat Duffy
1984 SK/SR #4113
Slàinte

Edited by - on

DavidCrosby
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USA
240 Posts

Response Posted - 06/06/2011 : 09:52:06

I think it should have a steady, solid stream regardless of engine speed.

I have a Honda 9.9 (rounded cover). When I bought the boat, the engine would not idle very well, but would run at higher RPMs without a problem. The stream was like yours minimal at idle, stronger with RPM increase. I thought my problem was a gunked up carburetor. I had my brother rebuild it and did not solve the idle problem. A boat neighbor with a Honda 8.? (rounded) stopped by one day while I was playing with the engine trying to figure out the idle. He said, I should have a solid stream at idle. I then pulled the lower unit to gain access to the impeller. It only had one blade left. I replaced the impeller and all engine problems went away and I now have a steady stream regardless of engine RPMs.

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pfduffy
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317 Posts

Response Posted - 06/06/2011 : 10:22:00

Was it difficult to remove the lower unit? I removed the bolts, pulled it down a bit and then lost my nerve as I could not see any way to disconnect the shift linkage without removing the pin where it connects to the shift lever.

Also - David - are you saying replacing your impeller resolved the idle issue?

Edited by - pfduffy on 06/06/2011 10:25:56

Sloop Smitten
Master Marine Consultant

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USA
1181 Posts

Response Posted - 06/06/2011 : 11:15:53

Pat,
You do need to disconnect the shift rod at the shift lever to remove the lower housing. If you look where the rod exits the engine housing (at the top) there is a set screw that connects the rod to the shift mechanism and also allows adjustments. I think the set screw takes an 8mm wrench and it is a tight fit. You might need to move some items to reach it. There is also a thermostat that opens as the engine gets warm and it may be salt encrusted and there are internal passages that the water for the outlet pass through that can become encrusted. Both the thermostat and those passages can be accessed via a cover on the same side of the engine as the throttle. Just trace the rubber outlet hose back to where it connects to the engine. If you are going to tackle changing the impeller you might want to clean those items at the same time. A new thermostat runs about $25.

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pfduffy
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317 Posts

Response Posted - 06/06/2011 : 11:33:07

Joe - if I remove that cover, is there a gasket set that I need before re-installing? Thanks for your help!

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Sloop Smitten
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1181 Posts

Response Posted - 06/06/2011 : 11:36:04

As I recall there is a gasket. Mine was reusable I believe but I do not know why you couldn't just run a bead of form-a-gasket. If you order a thermostat or impeller you can order the gasket as well.

Edited by - Sloop Smitten on 06/06/2011 11:36:34

DavidCrosby
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240 Posts

Response Posted - 06/06/2011 : 13:04:27

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by pfduffy
 Was it difficult to remove the lower unit? I removed the bolts, pulled it down a bit and then lost my nerve as I could not see any way to disconnect the shift linkage without removing the pin where it connects to the shift lever.

Also - David - are you saying replacing your impeller resolved the idle issue?
<hr height="1" noshade id="quote"></blockquote id="quote">

Looks like the question was answered. But, for my two cents - No, it is not at all difficult to remove the lower unit. Several bolts at the lower unit and a link, for the gear shift which is not much more than a long nut connecting two rods. The position of that nut is important. I had some problems with reverse after putting it back together. I had to play a bit with the adjustment of the nut a bit to work through that detail.

Regarding the idle, I later discovered that on my model Honda there is a thermal safety switch. It shuts the motor down when it gets too hot. The bad impeller was not cooling the engine at idle, so it would run for a short while and then quit.

I recommend ordering a shop manual from a Honda dealer. It is well worth the money. Replacing the impeller is not that difficult, but Marine outboard dealers seem to think it is rocket science and charge accordingly.

Edited by - on

TakeFive
Master Marine Consultant

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2272 Posts

Response Posted - 06/07/2011 : 06:54:58

The pee hole should squirt a solid stream at all motor speeds. My BF15A peed very slowly all last year, and was almost plugged when I went to launch this year. Like you, I could cover the hole with a finger and steam pressure would build up, and upon removing my finger the scalding steam would come out forcefully, followed by a slow drip of very hot water. This is NOT how it should be. [EDIT: My recollection was wrong. It was poking the hole with a wire that led to hot steam coming out. Putting my finger over it did nothing, because it was essentially completely plugged.]

I almost postponed my launch to remove the motor and take it to a dealer. As a last ditch attempt, I detached the hose from the plastic outlet fitting and removed the fitting from the motor. I put it up to my mouth and blew back hard on it. A hunk of dirt/sand/whatever came shooting out. I reassembled it and retested, and it now squirts very strongly at all speeds. We launched on schedule, and it works great.

Edited by - TakeFive on 06/07/2011 19:11:01

JohnP
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1520 Posts

Response Posted - 06/07/2011 : 12:03:01

Another easy fix is to poke a stiff wire (straightened coat hanger wire) into the outlet hole to try to clear it of any junk that has possibly accumulated in there.

I have a 2001 Honda 9.9 and it has a cooling water flush port on the port side under the cover. I bought the hose adapter and now wash the dirt and salt out of the cooling system with fresh water for a minute or two after each time out.

Other models of the 8 hp or 9.9 hp have a cooling water tube that can be fitted with a T-tube connected to a hose adaptor. Instructions for doing that are in the Technical Tips on the left of this Forum page.

Edited by - on

TakeFive
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2272 Posts

Response Posted - 06/07/2011 : 12:13:13

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by JohnP
 Another easy fix is to poke a stiff wire (straightened coat hanger wire) into the outlet hole to try to clear it of any junk that has possibly accumulated in there...<hr height="1" noshade id="quote"></blockquote id="quote">
FYI, that's the first thing I tried and it did not work for me. Whatever was in there was big enough that poking it back into the hose would just allow it to come back out and clog the pee hole again. That's why it was so important to remove the plastic pee hole fitting and blow backwards into it. That eliminated the clog permanently.

Poking a wire in might work for small clogs, but removing the fitting and blowing it out backwards could work better for some.

Edited by - TakeFive on 06/07/2011 12:16:18

Frank Law
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USA
159 Posts

Response Posted - 06/07/2011 : 13:32:11

Pat--- I agree with Rick I had no pee stream on my 8hp honda and it turned out to be a clog in the black hose from the motor to the pee port. I first tried a wire up the hose , that did not fix it .. Removing the hose and pushing a fattened wire thru the hose pushed out a wad of something and now it pees a lot better than me!!! Also I had idle problems and I think it cleared up when I cleaned out the hole at the back of the motor..I think its right below the cover latch its about 1/4-5/16" in diameter I believe it has something to do with idling. There was mud in the hole from setting the motor on the ground..

Frank Law
" ABOUT TIME "
3519 1983
Sr, swk

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pfduffy
Captain

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USA
317 Posts

Response Posted - 06/08/2011 : 07:23:11

Thanks for all of the responses! For those of you you own Honda outboards, how often do you replace the water pump?

Edited by - on

Frank Law
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USA
159 Posts

Response Posted - 06/10/2011 : 09:43:07

Pat ---I have replaced the Impeller 2x in the last 4 years , the blades were almost non existent .. I moor in shallow water and wonder if sand gets sucked up and wears away the blades . I have a 4 stroke 8 hp 2001 honda
Frank Law
About Time
# 3519 1983
sr swk

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panhead1948
Captain

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345 Posts

Response Posted - 06/10/2011 : 11:11:14

I have and older 7.5 honda about 86 and I had the impeller replaced for the first time after 20 years.

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