Should there be a Sleeve Propeller Bore on 200HP Merc 3.4L V6

[EagleMtn]

Having issues with intermittent engine vibration on 2019 Mercury 200HP 3.4L V6. 76 hours on the engine. This is a new problem that occurred at WOT. Initially I figured I hit something and damaged the prop, but can't see any external damage and engine has a vibration while idling in neutral as well (gets worse in gear under more rpm). Exploring possible engine/fuel issues without much luck, but won't go into that in this forum. Also important symptom to note is lack of power at higher rpm... WOT at 6000+ RPM and boat is topping out at 20mph... use to run mid 30's. I found some threads with issues that sound similar to what I am experiencing on 115hp and folks are talking about plastic sleeve propeller bores that prevent exhaust from escaping before the prop. I pulled my prop and there is no plastic sleeve propeller bore, so I figured that had to be it - problem solved? Went to Mercury parts catalog and cannot find this for my engine model... part is shown on every engine up to 150. So long story to ask this audience if anyone knows if this or a similar part should be present on a 200HP? Would welcome any other thoughts on potential issue I'm experiencing as well.

 

[Scott06]

I assume you are talking about the prop hub being broken ? https://www.amazon.com/mercury-prop-hub-kit/s?k=mercury+prop+hub+kit

 

[EagleMtn]

Thanks for your response. No I am referring to the bore sleeve which is a white plastic piece that seems to be evident in every Merc under 150hp, apparently fairly common this part breaks and when it does causes ventilation of prop. video here Pulled the prop on my 200hp and this piece was not here, but cant seem to find one in a parts catalog, so maybe it doesn't exist on 200hp engines. Thinking more about your response though... if the prop hub is broken or spun will the prop still spin at all? I've lost a lot of power but the prop is still moving. Also if either of these are the culprit I cant understand why I would have engine shaking while in neutral and idling. I will probably go pull it and look more closely at the hub, that's a good thought.

 

[QBhoy]

Not sure. But I know it only seems to be an issue usually found in the early 115ct and 150 gearbox from around 2014-2017 perhaps. After that (or maybe earlier by a little) they changed the design of the part. Shouldn’t affect things in neutral though, I’d say. Even if this was the issue.

 

[flashback]

Do you think it may have a steady miss?

 

[EagleMtn]

Do you think it may have a steady miss?

Yes, possibly. I pulled & inspected all the spark plugs and checked compression in all cylinders... everything from that perspective seems good. Dont have a timing light, is there a simple way to check timing?

 

[EagleMtn]

Not sure. But I know it only seems to be an issue usually found in the early 115ct and 150 gearbox from around 2014-2017 perhaps. After that (or maybe earlier by a little) they changed the design of the part. Shouldn’t affect things in neutral though, I’d say. Even if this was the issue.

Appreciate the intel & response. Ya, the shaking in neutral was why I originally moved on from some kind of prop issue, but the higher revs & lower power due to ventilation issues around prop that others described with the prop bore sleeve is very similar to the experience in performance I'm having (minus the shaking in neutral). IDK, I'm at a loss currently.

 

[QBhoy]

Appreciate the intel & response. Ya, the shaking in neutral was why I originally moved on from some kind of prop issue, but the higher revs & lower power due to ventilation issues around prop that others described with the prop bore sleeve is very similar to the experience in performance I'm having (minus the shaking in neutral). IDK, I'm at a loss currently.

Is it possible you might have damage to the steering bushes ?

 

[QBhoy]

Appreciate the intel & response. Ya, the shaking in neutral was why I originally moved on from some kind of prop issue, but the higher revs & lower power due to ventilation issues around prop that others described with the prop bore sleeve is very similar to the experience in performance I'm having (minus the shaking in neutral). IDK, I'm at a loss currently.

But to be honest…the odds on favourite to cause this, would surely be a fuel or fuel delivery issue, you’d think. Do you have smart craft gauges ? Does the rpm fluctuate at idle

 

[EagleMtn]

Is it possible you might have damage to the steering bushes ?

Anything is possible, how could I test this?

 

[EagleMtn]

But to be honest…the odds on favourite to cause this, would surely be a fuel or fuel delivery issue, you’d think. Do you have smart craft gauges ? Does the rpm fluctuate at idle

Don’t have smart craft gauges. RPM fluctuates btwn 900-1000 at idle

 

[EagleMtn]

Here’s some video… at idle, 1400 and 2000 rpm
View attachment IMG_1660.MOV
View attachment IMG_1660.MOV

 

[EagleMtn]

Don’t have smart craft gauges. RPM fluctuates btwn 900-1000 at idle

Also fuel delivery is one of my suspicions… changed fuel and replaced fuel filter. Ran some sea foam to hopefully clean out injectors. Holding out for hope it’s not fuel pump

 

[EagleMtn]

Here’s some video… at idle, 1400 and 2000 rpm
View attachment 366867
View attachment 366867

View attachment IMG_1660.MOV