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RPMs higher than usual

O

occh

Contributing Member
I have a Honda 130Honda and I went out today and noticed that my rpm’s were a lot higher than normal operation . Any thoughts ?
 
Higher at idle orfull throttle?

If your full throttle, on plane, rpm is higher, check your prop hub and make sure the rubber isn't deteriorating.

If the idle is suddenly higher than normal it could be a few things.
An intake leak...a stuck open thermostat...a failed engine coolant sensor....excessive fuel pressure if it's fuel injected.....a mis-adjusted choke if it's carbureted....sticky throttle linkage or cable...and probably a few other things that escape me at the moment.
 
jgmo said:
Higher at idle orfull throttle?

If your full throttle, on plane, rpm is higher, check your prop hub and make sure the rubber isn't deteriorating.

If the idle is suddenly higher than normal it could be a few things.
An intake leak...a stuck open thermostat...a failed engine coolant sensor....excessive fuel pressure if it's fuel injected.....a mis-adjusted choke if it's carbureted....sticky throttle linkage or cable...and probably a few other things that escape me at the moment.
Click to expand...

It seems to be when I give it throttle and I am underway. The engine seems to running fine except that I am over in rpms anywhere from 200-500 . The faster I go the number increases faster than normal. I never spun a hub so I have no ideas how to check. Somebody at my dock told me to put it in gear when off and try moving the prop. I tried it and the prop moved a bit. Does that mean it’s slipping.
 
Last edited:
It depends on what "it moves a bit" means.

There is some "inherent" movement in the transmission gear train so that, if the trans is locked in gear with the engine off, you can "rock" the prop back and forth a small distance as you take up the "slop" in the gears. But, when you move it that slight amount, in either direction, and remove the gear lash or "slop", you shouldn't be able to budge the prop any additional distance by hand. It should be completely locked tight. If it fails this little test, your prop hub is going bad and that IS the reason for your increased rpm.

I hope I made this clear enough for you to make a determination.

WARNING! Any time you are manipulating a prop by hand, keep the ignition off and the kill switch lanyard pulled for safety.

Good luck.
 
Another way to check, is to scratch a mark on the prop near the prop nut. Then also scratch a mark on the prop nut next to your other mark. You can use a knife or a center punch.

Then go run the engine under load on the water. Do several accelerations to put a lot a strain on the prop.

After your run, check the marks. If they moved away from each other, the prop has spun.

Mike
 
Just as an aside - whether your prop is spun or not, one of the things I've learned the hard way is to always carry a spare prop, castle not, flat washer, thrust washer, and cotter pins on the boat. Often, a spun prop will not fail completely all at once, but rather, over time, you will experience some slipping on acceleration. Don't ignore that.
 
jgmo said:
It depends on what "it moves a bit" means.

There is some "inherent" movement in the transmission gear train so that, if the trans is locked in gear with the engine off, you can "rock" the prop back and forth a small distance as you take up the "slop" in the gears. But, when you move it that slight amount, in either direction, and remove the gear lash or "slop", you shouldn't be able to budge the prop any additional distance by hand. It should be completely locked tight. If it fails this little test, your prop hub is going bad and that IS the reason for your increased rpm.

I hope I made this clear enough for you to make a determination.

WARNING! Any time you are manipulating a prop by hand, keep the ignition off and the kill switch lanyard pulled for safety.

Good luck.
Click to expand...

yes, I noticed it had slight movement back and forth that seemed to me to normal, but then with alittle more hand pressure it moved about 1/4inch .
 
hondadude said:
Another way to check, is to scratch a mark on the prop near the prop nut. Then also scratch a mark on the prop nut next to your other mark. You can use a knife or a center punch.

Then go run the engine under load on the water. Do several accelerations to put a lot a strain on the prop.

After your run, check the marks. If they moved away from each other, the prop has spun.

Mike
Click to expand...

Thanks Mike, I will give it a try. Let’s say the hub is slipping, can these things be rehubbed
 
chawk_man said:
Just as an aside - whether your prop is spun or not, one of the things I've learned the hard way is to always carry a spare prop, castle not, flat washer, thrust washer, and cotter pins on the boat. Often, a spun prop will not fail completely all at once, but rather, over time, you will experience some slipping on acceleration. Don't ignore that.
Click to expand...

Thats sound advice.
I only took off props once on a twin I/O I had about 8 years ago. Is it the same for outboards. Can you give quick refresher? Lol. I know there is a cotter pin there. What tools are needed ? Needle nose to get pin out then I am drawing a blank .

Thanks
 
Go to the Honda Marine site and download the Owners Manual for your engine.

https://marine.honda.com/support/manuals/models/BF225

In that, there are detailed instructions for removing and changing the prop. Be sure to grease the splines when you re-install or replace.

The only tools you need are a pair of needle-nosed pliers to straighten and pull the cotter pin, and a crescent wrench or pair of big channel lock pliers to loosen the hub nut.

You should pull the prop at every 100 hour maintenance, inspect for fishing line or anything else that might have gotten under the hub, check the fins for deformations, re-grease the splines, and re-install. When you pull the prop carefully inspect where the rubber hub connects for the outer prop itself, and where the rubber hub connects to the inner spline hub. If any of the rubber is raised, that's a sign that it has spun, and will fail. Be sure to use a NEW SS cotter pin.

BTW - most marine service shops have a relationship with someone who rebuilds props and will usually ship it out for you. The last one I had re-built, about 2 years ago, cost me $140 for a stainless steel 14.25 X 15 prop.
 
hondadude said:
Another way to check, is to scratch a mark on the prop near the prop nut. Then also scratch a mark on the prop nut next to your other mark. You can use a knife or a center punch.

Then go run the engine under load on the water. Do several accelerations to put a lot a strain on the prop.

After your run, check the marks. If they moved away from each other, the prop has spun.

Mike
Click to expand...

Hey Hondadude, I had the hub replaced but same issue rpms are higher. Normally approaching 3800-4000rpns prior , my boat was on plane. Now rpms read 5000 ish to be on plane. WOT use to be at 6500 now it’s slightly over 7000.
Would bottom growth factor into this equation
 
Yes, growth on the hull creates drag and the engine has to work harder to achieve the same speed.
Is your rev counter is set correctly on the back? I've heard that they can sometimes need checking.
 
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