Spun hub at high RPM issue

[99yam40]

Ferris thanks for searching and finding that.
My memory is not totally gone yet ,but I could not remember what the possible cause was.

too bad the OP on that thread never came back and reported what the fix turned out to be.

seems that the wrong trim tab could be the problem
or the tube is plugged with sand/mud/shell

or lower unit is not meant to run shallow( that high out of water without a low water pick up)
Thinking about that a little more, maybe Rod was saying that motors with low water pick ups allow them to run too shallow so not enough water is flowing across the prop causing it to over heat, so they designed the trim tab to scoop up water to run across the prop thru that tube
let us know what you find out.
it will help others

[DennisG01]

Well, that is some very interesting information regarding the special anode and the water tube. I just looked at it on a parts diagram and sure enough! Cool info!

[99yam40]

Well, that is some very interesting information regarding the special anode and the water tube. I just looked at it on a parts diagram and sure enough! Cool info!

I had a look just now at the parts break down and am not sure if the trim tab is the only special thing or not.
I wonder if there is a special prop for that too.

I still have no idea where the so called tube is that you need to clean out or at least make sure it is clear.

what if the scoop on the trim tab is not down in the water where it can scoop up water.
might need to lower the motor some to make sure it can grab some water after the OP verifies the proper trim tab is on that lower unit

[DennisG01]

I had a look just now at the parts break down and am not sure if the trim tab is the only special thing or not.
I wonder if there is a special prop for that too.

I still have no idea where the so called tube is that you need to clean out or at least make sure it is clear.

what if the scoop on the trim tab is not down in the water where it can scoop up water.
might need to lower the motor some to make sure it can grab some water after the OP verifies the proper trim tab is on that lower unit

I have no idea of the proper model number for his VMax, but I just randomly picked a 2009 (and later) VF225 from the parts link above. The anti-vent plate anode is referred to as a "cap", but it looks like it draws water in and shoots it up through a cavity to #21 Seal and then #19 Tube that simply dumps the cool water down into the exhaust cavity which, of course, goes out to the prop. Or, at least, that's how I'm seeing it?

https://www.boats.net/catalog/yamaha...casing-drive-2

[99yam40]

he wrote it was a

2009 Yamaha 225 VMAX HPDI.
so it would not be a F (4 stroke)

so it should be a Z , and I am not seeing that tube there

[DennisG01]

he wrote it was a

2009 Yamaha 225 VMAX HPDI.
so it would not be a F (4 stroke)

so it should be a Z , and I am not seeing that tube there

Ah. You are right. - only see a regular anode. https://www.boats.net/catalog/yamaha...casing-drive-2

Maybe a picture of this area of his engine would help to 100% clarify.

[99yam40]

Where did the delete button go?

[99yam40]

delete
not sure why it posted so many times

[DGEXPLORATION]

The beast in question.

[DGEXPLORATION]

Trim tab is pretty sacrificed, but I don't see how a brand new one would help cool the prop hub

[DennisG01]

Trim tab is pretty sacrificed, but I don't see how a brand new one would help cool the prop hub

It won't. Take a look at the link in my post #19 - that was when the guys were trying to help and figuring that you might have that special anode "plate" (not really an anode). But you don't have that - based on 99Yam's notation of that, the link that I listed in #21 and your picture. Too bad - that would have explained it.

But... in your picture, is that the height that you run the engine? "From the pictures", it appears way too high. Roughly speaking, the anti-vent plate should be about 1" higher than the transom keel for every 1' it is setback. Running the engine higher than that can severely limit the cooling ability of the engine and the ability for the prop to "bite". Could it also allow the prop to overheat? Maybe - don't know.

But if you're running the engine too high, that could very well be causing blowout.

[99yam40]

look at the props in all of the V 225s
seems they all had slots in the front of the prop until 2016
Does anyone think that is a especial prop?
very strange that al of those are unavailable

OP, if I were you I would be talking to the manufacturer of the boat to see what they have heard or ran into.

maybe go look at a new trim tab to see if it has a scoop in the front and than see where it would put any water it picked up.
could be something is plugged up or not catching any water because the tab is not in the water at high speed.

Op did this boat ever run OK at high speed with that motor on it?
maybe wrong motor on it now, or wrong lower unit if that was changed out some time ago

[DGEXPLORATION]

Spoke with an outboard tech at a Yamaha dealer today, and he thinks it’s a prop issue and I need to pitch down. He thought the jack plate was mounted just fine, and I would see more engine overheating or overrevving if that were the case. Also said the exhaust gasses came out hotter on the four strokes, which is why they have the special trim tab. I asked him if I could swap out to the 4 stroke trim tab and add the cooling tube, and he said that and other mods could be customized in that lower unit, if it is more than just the prop.
I have the engine jacked up on the hydraulic jack plate just to tow.

[99yam40]

But have you looked to see how high you trim it when running?
is the cav plate out of the water when running high RPMS? how far out?

most boats I have seen with jack plates are tunnels or pockets, yours does not look like it is either of those.

you can hear those boats from way off in the distance, I think the exhaust is not dumping under water at high speeds.
not sure if your prop stays low enough to keep the prop hub cooled off.


Have you tried to find out what prop a set up like yours normally uses and what speeds and RPM it can run?
Yamaha performance Bulletins use to be a good place to look.

let us know what you find out

[DennisG01]

Jack plate may be mounted correctly, but I'm not sure I completely agree with the mechanic's idea of it "not" overheating equaling the jack plate not being the problem. You may not have run it long enough to overheat since the prop started ventilating. Besides, as long as the water pickup is under water, you're still getting cooling water into the engine.

The fact that you can run at 4,200 leads one to believe that the engine is OK at a given height, but once you start running faster the anti-ventilation plate comes further out of the water since the boat is riding higher. Meaning, the anti-VENTILATION plate is no longer doing it's job. The anti-vent plate should, at most, be skimming just along the surface at full speed/plane. To see if the whole issue all long has been user error, lower the jack plate and/or trim down a bit and see if the issue goes away. You could also video it.

Swapping the anode for the water pickup plate sounds more like a band-aid than a fix.

It was brought up above, but never heard your answer... have you ever match marked the hub to completely verify it was/was not slipping?