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View Full Version : Honda 5hp 4 stroke troubleshooting, please...



JimD
08-27-2009, 09:30 PM
So I had the boat out for a few hours this afternoon and the motor ran fine at low rpm but when I opened up the throttle the revs rose and fell rhythmicly at the rate of a slow, deep breath - in, out, up down (anyone seasick yet). Anyone know what causes this? Is it possible I just did something dumb like forget to open the gas tank vent cap and it was fuel starved? It ran fine last week.

donald branscom
08-28-2009, 02:12 AM
So I had the boat out for a few hours this afternoon and the motor ran fine at low rpm but when I opened up the throttle the revs rose and fell rhythmicly at the rate of a slow, deep breath - in, out, up down (anyone seasick yet). Anyone know what causes this? Is it possible I just did something dumb like forget to open the gas tank vent cap and it was fuel starved? It ran fine last week.

Jim- Check the thermostat. It may be full of salt crystals if you were in salt water.
The engine gets hot and it can get completely clogged and and the engine can over heat.
IS the prop the SAILBOAT prop? If not the pitch may be way too much.
The SAILBOAT HONDA prop is made for pushing heavier boats.
Your boat is no light skiff . Right?

On the other hand a fuel tank vent is something to check.

TerryLL
08-28-2009, 07:51 AM
Jim,
You're not alone. I did a quick google and got several hits about the 5HP Honda with surging problems. I didn't find a definitive solution, but possible things to check are the prop hub slipping and the carb jets partially plugged. Is this motor in a well where it is possibly sucking in the exhaust gasses?

Woxbox
08-28-2009, 07:57 AM
Replace the fuel filter, too. That can restrict flow and create that sort of problem.

JimD
08-28-2009, 08:19 AM
Thanks for the replies. I wish now I'd taken that small engine repair course advertised on the match book covers instead of going to art college.

1 - small prop, not sailboat prop, which I would prefer but am saving my pennies for a yamaha 8. We were also in a fresh water lake last time out so it shouldn't have been all salted up. But I will look for a thermostat.

2 - yes, the motor is in a well but it is fairly well vented and it ran fine last week in the well.

3 - I'll replace the fuel filter.

Also, it seems to run a little rough and stalled on me as I idled in to the dock.

Lance F. Gunderson
08-28-2009, 08:47 AM
I have a new Honda 5hp four stroke. I've also had and am having problems with it which I can't explain. It's guaranteed for five years but I haven't had time to take it back to the dealer I bought it from yet. It always starts hard...have to pull the cord many times. It usually stalls when I put it in gear. The throttle does not work...you turn it and nothing happens, then all at once it accelerates. Mine also runs at different speeds all by itself. I'm going to take it back and bitch.

TerryLL
08-28-2009, 08:49 AM
Well, running rough, stalling, and surging sounds pretty much like a fuel problem.

Did this start right after a fuel fill-up? Maybe some bad fuel.
Did you switch fuel types? Ethanol? Fiberglass tank?

Change the fuel filter and check for unrestricted flow from tank to motor. Put some fuel in a clear glass and do a visual check for contamination. Check for kinked fuel lines inside the motor and insure that all the clamps are tight, especially on the suction side of the fuel pump, all the way back to the tank. A small air leak in the fuel line will starve the engine and result in surging.

JimD
08-28-2009, 08:53 AM
Well, running rough, stalling, and surging sounds pretty much like a fuel problem.

Did this start right after a fuel fill-up? Maybe some bad fuel.
Did you switch fuel types? Ethanol? Fiberglass tank?

Change the fuel filter and check for unrestricted flow from tank to motor. Put some fuel in a clear glass and do a visual check for contamination. Check for kinked fuel lines inside the motor and insure that all the clamps are tight, especially on the suction side of the fuel pump, all the way back to the tank. A small air leak in the fuel line will starve the engine and result in surging.

Roger.

JimD
08-28-2009, 08:55 AM
I have a new Honda 5hp four stroke. I've also had and am having problems with it which I can't explain. It's guaranteed for five years but I haven't had time to take it back to the dealer I bought it from yet. It always starts hard...have to pull the cord many times. It usually stalls when I put it in gear. The throttle does not work...you turn it and nothing happens, then all at once it accelerates. Mine also runs at different speeds all by itself. I'm going to take it back and bitch.

Mine starts easily with just a couple pulls. In fact it sat for a year in the garage and still started on the third yank. Mine is quite old. 1990's, not sure exactly. It hasn't stalled when I put it in gear yet.

darroch
08-29-2009, 12:57 AM
had kind of a similar problem with 2 hp 4 stroke Honda...thought it was old gas (only a week old, though)...threw a few ounces of methyl hydrate in the tank and it solved the problem

another time I used the most expensive gas (high octane) and it wouldn't start...threw some methyl hydrate and it worked fine...this motor likes the cheap stuff

kazeai1969
08-29-2009, 04:33 AM
I had a Honda8 for a bit before it stopped running....have fallen in love with my Tohatsu Sailpro...6hp with alternator.

JimD
08-29-2009, 08:55 AM
I had a Honda8 for a bit before it stopped running....have fallen in love with my Tohatsu Sailpro...6hp with alternator.

Regarding the Tohatsu 6, do you know if a control box is available or tiller steering only? Hard to tell from their website.

JimD
08-29-2009, 08:57 AM
A couple buddies at work seem to think the surging is a carb problem. Regardless, I picked up a new fuel filter and spark plug yesterday, and changed the dirty oil for good measure. I will poke around the carb to see if anything is obviously sticking.

Tylerdurden
08-29-2009, 09:02 AM
Chances are its to do with ethanol in the fuel. Pulling the carb and cleaning it may be the only solution. Its best if your going to let it sit for any length of time to run the motor dry of fuel. That will cut down on those issues. I have had several OB come to me with similar issues as of late. It used to be down on the list but I am finding once I know its pumping to the carb its the next step in the process. I keep a rebuild kit with min for that reason.

Cannot wait for an injected deisel OB.;)

JimD
08-29-2009, 09:10 AM
... Pulling the carb and cleaning it may be the only solution.

How do you clean a carb? As you can see I'm not a motorhead.

Tylerdurden
08-29-2009, 09:26 AM
How do you clean a carb? As you can see I'm not a motorhead.

I have to find the manual for your motor for details. You need to pull it off, tear it down, have a couple of cans of carb cleaner and a gasket set minimum. If I remmeber correctly there are float adjustment too so a steel rule will be needed.If you have an auto paint store nearby get a spraygun cleaning kit for the little brushes and wire probes.
I suggest if you do not have a service manual get one as it will guide you step by step with all the specs you need.
If I can find mine I will scan an pdf it to you but I think mine is for a very early model tha may not be the same as yours.

First thing though is to pull the bowl and check the contents. If there is crap in there chances are the jets are plugged somewhat and with what your decribing I am thinking its the high speed or float sticking.

john l
08-29-2009, 09:31 AM
ethanol is hygroscopic and corrosive. probably your problem. too bad gas cans don't have a valve at the bottom to drain off the water. my pilot friends will dump the water out of the tank. they open the valve and let the clear liquid out ( water is heavier than fuel).

Tylerdurden
08-29-2009, 09:46 AM
I am seriously considering building a vacuum still. Only real cure I can think of with the crap gas we get these days. Sta-Bil sure but the last two years I stored any with it, seemed to go punk twice as fast as before.

JimD
08-29-2009, 10:14 AM
I have to find the manual for your motor for details...

There's an on line pdf manual but there's not much in it. Nothing about carb maintenance and repair: http://www.honda-marine.com/mar_pdf/31ZV1630.pdf . I work today but this evening I'm going to fire it up with the new plug and fuel filter and see if that made any difference.

Tylerdurden
08-29-2009, 10:27 AM
That's the owners manual. This is what you need.

http://www.repairmanual.com/marine/4/12878

JimD
08-29-2009, 10:43 AM
That's the owners manual. This is what you need.

http://www.repairmanual.com/marine/4/12878

Thanks for that, Mark.

JimD
08-29-2009, 11:29 AM
Talked to a Honda guy who suggested I try Seafoam

http://www.supermotors.net/getfile/217841/fullsize/Sea%20Foam%20Can.JPG

http://www.seafoamsales.com/

Anyone have any experience with it?

Tylerdurden
08-29-2009, 02:39 PM
If you have to wait for a manual and want to get out there it is worth a try. Clean tank and fresh gas with that.

kazeai1969
08-29-2009, 05:37 PM
Not really sure Jim, but now that you mention it a control box would make a lot more sense that my current set-up....
http://www.flickr.com/photos/40735228@N03/3750816146/in/photostream/

JimD
08-31-2009, 11:20 AM
Not really sure Jim, but now that you mention it a control box would make a lot more sense that my current set-up....
http://www.flickr.com/photos/40735228@N03/3750816146/in/photostream/

I emailed Tohatsu and yes, it can take a control box. So that is good news. A Tohatsu 6 is likely a better option for me than a Yamaha 8. And thanks for the pics. That's quite a reach to the motor tiller on your transom.

JimD
09-02-2009, 06:34 PM
Motor isn't surging anymore. I changed the fuel filter, spark plug, engine oil, drained the carb, and plugged in a tank with fresh gas and an anti-gunk fuel additive called 'Small Engine Tune Up.' Seems to be running much better now.

Tylerdurden
09-02-2009, 06:47 PM
Motor isn't surging anymore. I changed the fuel filter, spark plug, engine oil, drained the carb, and plugged in a tank with fresh gas and an anti-gunk fuel additive called 'Small Engine Tune Up.' Seems to be running much better now.

Get the manual, don't wait for next time. I am glad it worked though.

JimD
09-02-2009, 07:47 PM
Get the manual, don't wait for next time. I am glad it worked though.

I will get the manual. Promise :).
And then I will save up for a new motor.

darroch
09-02-2009, 07:56 PM
ethanol is hygroscopic and corrosive

Is methyl hydrate 'anti-hygroscopic' too? Gets me through Air Care every year...