How do you replace the impeller on a Honda 90?

C

ccflyer

New member
So the engine's over heating and not pissing any water - those "in the know" suggest it's the impeller.

I take a 1/2 hr drive to the Honda dealer who sells me an "impeller kit" and says replacement is a snap - just have to remove six bolts.

Now I'm looking at the shaft and it seems a lot less like a snap.

Has anyone done this and, if so, can you take me through the procedure?

Thanks
 
Before you go tearing into it check the discharge end. A little wire to probe and remove the junk from the discharge end. More times than not this is the cause of your Engine not pissing. I found a straightened out fish hook works good for this in a pinch. If your at home with your boat flow water using the ear muffs things (tech. term unknown) and if you get no discharge you know you have an occlusion and not necessarily a bad impeller. Try this first. Its rare your impeller just quits .

My money is on some junk about 1/2" inside the discharge end.

Christopher Bulovsky
 
Thanks Chris but I checked this out with ear muffs b4 launch and it was "pissing" out OK -

the "folks in the know" think that's because the water is under pressure when using a hose .....??
 
I've only done Johnsons but the Honda can't be THAT different. Go to I-Boats and search the Honda database. Get a factory manual. Take lots of pictures so you can share your mechanical prowess with all the Honda owners here. Finally, get one of these IMG_2136.sized.jpg
 
As Pete shows in his picture there are two shafts that go to the top of the motor. The Driveshaft is splined and will usually easily slip on and off. The gear shift is a totally different story. On the old Honda kicker I have it is a royal pain to undo the shift linkage to remove the lower unit. It might be an easy job with the bigger motors though.

Get yourself a manual and look at the shift linkage portion very carfully before you start. On my kicker it has a special nut that you have to unscrew. And when you re-install it you need to correctly set the height of the nut to get the motor to shift correctly.
 
The shift shaft for the Honda 90 should be splined and slip straight down and out of the coupling the same as the drive shaft does. Even if your impeller isn't needing to be changed, I was advised by Larry at Sportcraft Marine to remove the lower unit to grease the splines on the two shafts every three years. He also said that since the lower unit is off, I might as well change the relatively inexpensive impeller at the same time. Use a marine grease on the splines when reassembling so that it will come apart easily the next time you do it.

Getting the impeller changed is pretty easy to do. Remove the bolts as the dealer said and wiggle/tap the lower unit assembly downward to disengage the fit between the two sections. Then continue pulling it straight away from the power head until the shafts are clear. The lower unit is not heavy, but it can be kind of awkward and not balanced when it comes free. You can do it alone quite easily - just don't let anything surprise you. Make sure the motor is tipped up high enough and there is nothing in the way behind or below it to keep it from coming out in one motion.

When it is out, it will look pretty much like the Johnson pictured a few posts above. The impeller is under the can slipped over the drive shaft. After the can/cover is removed (I don't recall exactly how it is fastened), the impeller slips up the shaft and off. There is a weird little key in the bore of the impeller, and you should have gotten a new one in the kit. Be careful with the new o-ring gasket so you don't stretch or deform it.

Probably the hardest part of the whole task is putting the can/cover back over the stupid impeller. The vanes are stiff and you need to be sure and apply plenty of marine grease to the vane tips and inside the cover, so the things are slippery and onery when trying to get them all laid over to fit inside the cover. You can use the old impeller to figure out which way the vanes belong when reassembling. The impeller is made such that it can only slip on over the key one way so you won't be able to put it upside down or forget how the old one came off. Don't forget the key and the grease. The grease is to protect the rubber the first time it is cranked over to start.

Putting the lower unit back on is easy. Sometimes you have to fiddle with the drive shaft to get the splines lined up, but once it engages the whole thing goes together good. (Don't shift the gears by rotating the splined shift shaft while it is out. I'm not sure whether it will still line up if it's out of position relative the the top half, but if it does it could be problems.) Tighten the bolts up in a cross pattern until the fit between the two sections is completely seated and then torque it to whatever it is supposed to be torqued to. Not too many people use a torque wrench on the thing, but a good snug push on a standard end wrench is just right. The tapped aluminum will strip easier than steel, so don't get things too tight. Also, go around the bolts a couple three times to make sure the fit is completely bottomed out. That's it - you're good to go.

Probably a little more detail than you needed, but that's the way both my old Honda 75 and my present Honda 130 work. The Honda 90 uses the same lower unit as those other two motors, so yours will be the same.
 
A couple additional notes:

By "standard" wrench, I meant normal length. The wrench itself will be metric.

Gary is right about the threaded shift shaft on the smaller Hondas. My old-style 15 has the same as he described. Those shift rods go up and down to do their thing. The larger motors have shift rods that rotate.

The first time I saw the impeller changed was at the dock in Friday Harbor. Les of EQ came across from Deception Pass and did his first ever Honda lower unit removal on a boat in the water. The impeller and sevice were covered by warranty, and for Les to launch his dad's TC with radar and come across in the fog cost me a plate of bacon and eggs that my wife cooked while he worked. Nice guy, huh? The C-Brat network worked pretty good that day. I called Fred, I believe it was, for local advice on getting service, he called Brock who called me, and we discussed options since there was no way to get service before my vacation time ran out. Just as Kay and I were debating whether to cross Rosario on the kicker or pay right around $300 total for ferry rides forth and back and forth again to get the truck and trailer, the phone rang again and it was Les. He said to have a good night and he would see us in the morning. From what I understand, the whole family is like that. I wonder where they got it?? Anyhow - I have done it a couple times myself since, and it is a whole lot easier with the boat on the trailer.
 
I would say it is damn near impossible except for millwrights and mechanics...looking at these pics, anyone who would tell you it is "a snap" should be taken out and shot!
 
Great description Mike! Having the shift shaft splined makes things much easier.

Pat, I suspect that we could change your impeller in less than an hour if you wanted me to walk you through it :)
 
As a preventative measure, keep in mind that if you leave your engine idle all winter sometimes the impeller vanes will "freeze" or bond themselves to the race. Then in the spring when you fire it up the first turn tears the vanes off. The impeller can be perfectly good but this will cause it to fail. I finally learned and go out and turn it over every couple weeks just to turn the vanes to a different spot. You can even do it by hand, just put it in gear and turn the prop by hand a partial turn. Impellers seldom fail, it is usually the vanes freezing to the race. An impeller can run for years and just gradually fade away, especially in sandy or turbid water.
 
Folks,

BE VERY CAREFUL OF TURNING THE PROP BY HAND WITH THE MOTOR IN GEAR!! THIS IS NOT CONSIDERED SAFE!!

Be ABSOLUTELY SURE that the key is not 'ON'. If the motor fires, you could lose some of your hand!!


The only safe way to turn a motor by the prop is to first REMOVE the spark plugs. Just pulling the plug wires off the plug is not enough. The rubber plug wire wants to jump back onto the plug.

Remember that older 2-stroke motors and all kickers make spark by rotation, not by the battery!! And ANY kicker motor can fire when turning the prop by hand with the motor in gear. On rope start motors, turn the motor by the pull rope. TO BE SAFE, DO NOT TURN THE PROP BY HAND IF THE MOTOR IS IN GEAR!!!


Shifting the motor into gear when not running can damage the shifter(dog clutch), shift cables, or control box. An outboard shifter(dog clutch) has square 'dogs' which fit into square recesses in the gear. If the 'dogs' are not aligned with the recesses in the gear, it won't shift and forcing the lever can cause damage.

If you must shift a non-running motor, have someone 'rock' the prop back and forth to align the clutch dog.(Hold the prop by the round exhaust hub, not by the blades.) When shifting a running outboard, 'snap' the lever from neutral into gear. DO NOT slowly 'slide' the shifter into gear. If you hear a rachetting sound when shifting, you are not moving the lever fast enough.

Shifting a motor running on a flusher is NOT recommended. Its dangerous to have the prop spinning in the air and the prop will 'coast' (spin) longer in air than it would in water.

In my long experience as an outboard mechanic and o/b owner, I have never had an impeller 'freeze' to its housing and then tear the blades. I am not saying that it couldn't happen, but I have stored my motor and worked on stored motors and not had that problem. However, starting an outboard 'dry' (without being in the water or on a flusher) will melt the rubber impeller to the housing. It only takes a few seconds of the motor running to melt a dry impeller. Old impellers can become brittle and the tips of the blades can break off so changing the impeller after two to three years is not a bad idea.

End of rant!! Please be safe when working on your motor!!
 
Larry-

Good information!

I have a related question for you:

When I had a 13 lb stainless steel prop on my Yamaha 90, I really noticed the weight or mass of the prop when shifting.

The "ClunK" with that prop was several times as big as with a 3-4 lb aluminum prop.

So the question is this- are stainless steel props harder on the shift dogs of the gearcase?

Thanks, in advance!

Joe.
 
Joe,

I never thought about it that way, but there is more rotational inertia (energy) in a heavier (SS) prop. It could cause the clutch dog to wear out or fail sooner.

When using a SS prop its probably a good idea to pause in neutral before shifting to the other gear, ie: Forward to Reverse to let the prop stop spinning.

In my experience, most clutch dogs are replaced because the leading corner of the dog is rounded off causing the gearcase to jump out of gear. Most likely caused by the operator not 'snap shifting' the motor.
 
ccflyer

Changing the impeller on a Honda 90 is not that big of a deal. In the next several days, I'll post some photos and info from their shop manual that should have you on your way.

Alma's Only
 
To wrap up my response to your question, the 5 bolts you loosen to drop the lower unit are easy to locate. One is just above the vertical plane of the propeller blades, in front of the trim fin which bolts to the lower unit, from the bottom. This bolt is a 10x80 hex head. The other 4 are on the same approximate elevation as the first, just under the horizontal fin of the lower unit (don't know what that's called - how about PSP for prop spray preventer), and are 10x40mm hex. Retorque all to 25 ft-lbs. after realigning onto the two dowel pins.
 
ALMA'S ONLY

Great job of posting photos and explanations from the Honda Shop Manual!!! Thanks from everyone who will find this extremely helpful! Joe.
 
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