Honda 5 HP 2007 -- Revs high in neutral with low throttle, low revs in gear

[fheller]

I have a 2007 HP 5 Honda. New to me. Sometimes (often) when it is in neutral, even if the twist throttle is low, the engine will rev very high and stay there. I would also say it does not rev high in gear; it seems kind of slow in fact. Engine is on sailboat on mooring, so I am hopeful for easier-to-try solutions I can do from the boat or dinghy.​

 

[km1125]

Sounds like you might have something loose in the throttle cable linkages. Open the cover and take some pictures. And look at the cables and linkage as you're moving the throttle around. The engine doesn't have to be running to do this, and if it's not you can put it in gear so you get the full range of motion on the throttle.

 

[fheller]

Okay, a photo and a video - prompt any ideas? Thank you!
View attachment IMG_2236.mov

 

[km1125]

Well, at least from that video it doesn't look like the throttle cables are the culprit.

You have a tough one here. About how high would you say it's revving in neutral?

The only way for the engine to really rev is for it to get more gas AND air. Timing changes can make it go a little higher or lower but not by a whole lot. For it to get more gas it could be a float thing, but then it would also be having to get more air or it would just flood out. The only way for it to get more air is for that throttle to open.

If it was running really rich at idle and there was a vacuum leak, then it could surge a bit, but I wouldn't expect it to rev really high.

When you write "it does not rev high in gear; it seems kind of slow in fact", expound a bit on that. It's a small motor trying to push a (relatively) large sailboat, it's not going to rev really high unless you have a VERY small prop. On some of those motors you can get a "high thrust" prop but that's only a step or two below the stock one, so it's still not going to let the motor rev really high.

 

[Scott Danforth]

Only one drop of fuel is needed for the motor to spin in neutral. You need fuel to rev under load.

I think you have a fuel system issue

 

[fheller]

Well, at least from that video it doesn't look like the throttle cables are the culprit.

You have a tough one here. About how high would you say it's revving in neutral?

The only way for the engine to really rev is for it to get more gas AND air. Timing changes can make it go a little higher or lower but not by a whole lot. For it to get more gas it could be a float thing, but then it would also be having to get more air or it would just flood out. The only way for it to get more air is for that throttle to open.

If it was running really rich at idle and there was a vacuum leak, then it could surge a bit, but I wouldn't expect it to rev really high.

When you write "it does not rev high in gear; it seems kind of slow in fact", expound a bit on that. It's a small motor trying to push a (relatively) large sailboat, it's not going to rev really high unless you have a VERY small prop. On some of those motors you can get a "high thrust" prop but that's only a step or two below the stock one, so it's still not going to let the motor rev really high.

I'll have engine running tomorrow (Sunday) to say more on that 'slow effect' when in gear so not my flawed 2 week ago memory; will do video. Also will be running Seaform through then.

 

[fheller]

Only one drop of fuel is needed for the motor to spin in neutral. You need fuel to rev under load.

I think you have a fuel system issue

May be right on the fuel system; next try is running Seafoam to see if clears anything out.

 

[Scott Danforth]

May be right on the fuel system; next try is running Seafoam to see if clears anything out.

There is no mechanic in a can.

Pull the carb apart and clean it

 

[km1125]

Looking at that video again, you might need to do some cable adjustments. HOWEVER, THIS IS NOT CAUSING THE HIGH RPM IN NEUTRAL. It's just something you should do (or check), as you might not be opening the throttle up to 100% when you move the handle all the way.

If you look at the picture below, you can see a pretty good gap in the linkage on the left, but when you start moving the throttle, that gap closes. A TINY amount of play is fine, but with the amount showing you might not be getting the throttle all the way open.

 

[fheller]

Looking at that video again, you might need to do some cable adjustments. HOWEVER, THIS IS NOT CAUSING THE HIGH RPM IN NEUTRAL. It's just something you should do (or check), as you might not be opening the throttle up to 100% when you move the handle all the way.

If you look at the picture below, you can see a pretty good gap in the linkage on the left, but when you start moving the throttle, that gap closes. A TINY amount of play is fine, but with the amount showing you might not be getting the throttle all the way open.

View attachment 378715

Thank you, I will look most closely at that and see if there is an adjustment I can make!

 

[fheller]

May be right on the fuel system; next try is running Seafoam to see if clears anything out.

It seemed to do better today in neutral; maybe the Seafoam is helping (or covering up a problem while it works through). Stayed 'tuned.'

 

[fheller]

The high rev problem seems to have abated (for now) either due to Seafoam or a spritz of WD40 on the linkage.
Still need to investigate the linkage to see if it is preventing full power in forward.
For now, thank you to all. That high rev was unnerving and distracting given how important neutral is when using mooring...