Tohatsu 6HP Problem

[eweb101]

Hi all,


I have a little Tohatsu 6HP outboard that's about two years old.



Just recently it started popping out of gear under heavy load, meaning that it revs really high and I lose propulsion. It's not really out of gear because all I do to recover is back off the throttle to idle and the propulsion returns.



Anyone had this problem and has figured it out?

[WSMFP]

Sounds like you spun the prop on the rubber prop hub. Basically the part of the prop with the blades is slipping on the rubber insert between the prop shaft section and the outside part with the blades. If that makes sense..............

[eweb101]

Originally Posted by WSMFP

Sounds like you spun the prop on the rubber prop hub. Basically the part of the prop with the blades is slipping on the rubber insert between the prop shaft section and the outside part with the blades. If that makes sense..............

I should've said that the engine really does work well at low, medium and even high RPMs. I use it every day to get to and from shore. It's only under high load like trying to go full throttle with 6 full jerry cans and 2 people that I see the problem.


Knowing that, do you still think it's the rubber insert?

[thomm225]

I had an impeller that did that or something similar to that (on my 5 hp Mercury)

The outboard stopped pumping water.

When I took out the old one it looked fine until I inspected it closer and noticed the hub was totally separated from the rubber impeller section.

[SwellGuy]

Originally Posted by eweb101

I should've said that the engine really does work well at low, medium and even high RPMs. I use it every day to get to and from shore. It's only under high load like trying to go full throttle with 6 full jerry cans and 2 people that I see the problem.


Knowing that, do you still think it's the rubber insert?

Yes.

[TampaTom]

The prop is "spun". Take it to a prop re-builder.

[eweb101]

Is the rubber part, part 8 in the attached photo?

[SwellGuy]

I don't think so but maybe.

Its in the prop itself. Its so that if you hit a rock or something you don't ruin your whole outboard, you just damage some rubber inside the prop.

[WSMFP]

Originally Posted by eweb101

Is the rubber part, part 8 in the attached photo?

No. Part number 8 is a thrust washer. The rubber part is inside the prop hub. You need to remove the prop and you can see it. It won't have a part number because it's not replaceable by your average user. You will need to take the prop to a dedicated prop shop and have a new rubber hub pressed in. I would just order a new prop to use while that is being repaired so you can have a spare when done.

[eweb101]

Originally Posted by WSMFP

No. Part number 8 is a thrust washer. The rubber part is inside the prop hub. You need to remove the prop and you can see it. It won't have a part number because it's not replaceable by your average user. You will need to take the prop to a dedicated prop shop and have a new rubber hub pressed in. I would just order a new prop to use while that is being repaired so you can have a spare when done.

Ok. Got it. The prop is only $81 so not too expensive.


Is there any way to test to make sure that's the problem before I order the new prop?

[Dsanduril]

Originally Posted by eweb101

...Is there any way to test to make sure that's the problem before I order the new prop?

Keep using it and it will get progressively worse. First one jerry can in the dinghy, then none, then it won't run at mid-speed. There's humor there, but also some truth. Each time you spin the shaft without spinning the prop you wear the rubber a bit more, the fit becomes a bit looser, and the next time it spins a bit sooner.

You can sometimes pull the prop and see bits of rubber coming out as the hub falls apart.

https://www.youtube.com/watch?v=5K2ob4LXWfo

[DougR]

To test for a spun hub, remove the prop and clean the grease off of the splined inner hub where it fits on the shaft. Using a fine punch, make a small punch mark on the end of the inner splined hub, and another punch mark on the outer hub adjacent to and inline with the first punch mark. It may also be possible to make the marks with a waterproof marker.

Now reinstall the prop and duplicate the load conditions where the problem occurs. After experiencing the problem again, remove the prop and examine the position of the punch marks. If the hub has spun, the marks will most likely be misaligned. It's very unlikely that the hub will have spun and then stopped exactly where it was to begin with.

DougR

[SwellGuy]

Originally Posted by DougR

To test for a spun hub, ...

Hey that's clever

[kev_rm]

Funny to come here and see this thread, I just had this issue with my merc 5hp - mainly due to age in my case (10+ year old prop). It acted a lot like cavitation was happening (not totally "out of gear", but losing force and increasing rpm) I bought a new prop (and a spare..)

[eweb101]

I decided to order a cheap third-party prop from Amazon. It should be here in a few days. I'll install it and report back if that fixes the problem.


Thanks for all the replies (and the jerry can humor). I'll be so relieved if something as simple as changing the prop is all I need to do.