Yamaha motor making whining/rubbing sound in lower unit

[Wilson]

Hey everyone,

I’m having some issues with my motor, specifically the prop/lower unit.

Boat sat in Marina for about 2 months and when taking it out recently I noticed I couldn’t get the boat to go past 10mph. Motor didn’t sound any different and when accelerating forward everything felt normal, however, when pushing throttle it would just stay at 10 mph even when reaching WOT. Motor didn’t seem to struggle or act different, just wouldn’t get up to speed. Tried this a couple times over several weeks and all with same results, couldn’t get boat past 10mph. Also to note tach would climb normally but only reach max 4000rpms and no more.

Doing my own research I came across two situations that seemed to me to be the most likely cause. First was a spun hub on the prop, second was fouling buildup on bottom of boat.

I started with spun prop since it was the easier of the two. After installing a new prop and running it for about 5seconds I realized something wasn’t right (ie, clanking noise, I believe boat started to move in reverse slightly). And FYI I installed new prop as correctly as I could and was very very careful. Thruster washer and spacer, nuts, washers all put in correctly. Lube on everything. And no I didn’t install prop backwards. I did my research.

So after this I put the old prop back on making sure everything was installed correctly in its place and everything lubed. Spinning by hand in neutral was rough, some resistance and a little clank noise. After awhile it spanned a little more smoothly.

Starting the engine up with the old prop back on and shifting into gears seems normal(I am tied to dock so can’t open her up). However running in neutral I now get a whining/rubbing sound coming from lower unit. I haven’t taking boat out to see how it performs because I’m worried about lower unit damage and motor dying becoming dead in the water.

below are a couple YouTube links to videos of the sound. I would love to get some ideas on what people think. My next step is to tow her to ramp and get boat out of water to drain lower unit oil and see if it’s milky and see if there’s metal bits. I realized until I do that the answers could be many but was just hoping for peoples opinions.

Boat/motor info:
2003 Triumph 190 Bay
2003 Yamaha f90 4stroke


Thanks and have a good 4th.

 

[Dave LeGear]

Lower unit gearing has an issue and shocked it is moving at all... Drain the lower unit oil and see if you have any metal in it? If not, would recommend some quality lower unit / gear oil like Royal Purple

https://royalpurpledirect.com/max-gear-75w-90-synthetic-gear-oil/

Plus, I would also check the shifter cable adjustment and make sure she is going totally into forward gear and not just halfway engaged?

 

[dboyd351]

You are making some good progress in sorting it out. Spun hub was a good first guess. Pulling it and draining lube is also good idea. Milky fluid means a bad seal. Metal shavings/particles indicate gear damage. If it is just milky might want to pay a mechanic to replace the seals and look at the gears while at it.
As Dave said, check to make sure gears are fully engaging/disengaging.

Before spending a lot of money keep in mind the motor is 20 years old. Might want to research the motor's book value versus repair cost. Also look at what your replacement options are.
Good to know those things before deciding on whether to foot a big repair bill.

 

[Dave LeGear]

OEM rebuilt lower units are always an option and (usually) for a few bucks more than the parts for have one rebuilt (if even needed?) some things are just much better handled at a shop that has done such hundreds if not thousands of times...

Pull a search on "Yamaha rebuilt lower units" and see what you can find for your model so, you have all the data needed to make the logical choice again if needed...

I agree though, trade in value for a newer more efficient engine (pending your plans on keeping the boat?) might be in the long run the best route to take if it is shot and needed replacement. No need to spend several grand on a rebuilt lower unit only to have another issue with the present engine then mandate spending that much or even more to (then) correct that.

 

[Wilson]

Thanks for the info. I appreciate you taking the time.

I was able to look over the shifter cable adjustment under the top cowling and moving it to forward/neutral/reverse seems like it’s fully engaging to where it needs to be. Forward fully moves forward all the way to end, reverse fully engages all the way to end. And neutral seems to sit in the middle. It’s hard to line up the neutral lines as I’m not seeing them clearly, but seems to be correct.

I have the boat in the marina so I need to get it on the trailer but it’s crazy at my boat ramp this weekend because of the 4th and bringing a limping boat to the launch seems like a bad day waiting to happen. So I’m researching and asking online what people think while I wait before looking at the lower unit oil condition. I’m sure that will give me some clues on where to go next.

I would love to post back an update and get your opinions. Hopefully by the end of the week.

Thanks again

 

[Dave LeGear]

Or we can chat on the phone or a zoom meeting online if that would help after you get it back on the trailer and had a chance to drop the drain and see the condition of the lower unit oil.

 

[Wilson]

Or we can chat on the phone or a zoom meeting online if that would help after you get it back on the trailer and had a chance to drop the drain and see the condition of the lower unit oil.

Great, I will take you up on that. Appreciate it. I plan to document what I find as I go so hopefully pictures/videos will show some clues.

Will keep posted, thanks again

 

[Dave LeGear]

Who knows, might even make for an article subject on Flats Nation!

https://www.flatsnation.com/blog/categories/skiff-and-bay-boats

 

[Wilson]

Ok so finally got the boat out of the water and was able to drain the lower unit oil. Attached are some photos best I can get but it seems like the oil is dark but not milky, which is good. The lower unit drain screw had a good amount of “very fine” metal pierces attached to the magnetic part but not seeing any larger metal pieces. Also the oil itself doesn’t seem to have any large pieces only “very fine” particles. I want to say that this is a positive sign? I hope.

I’m going to fill the lower unit back up with the Royal Purple oil tomorrow so I can start the motor again to see how it sounds. Fingers crossed.

Let me know what you think, I’d appreciate it.

 

[Harper]

My opinion .... those flakes of metal are not good. Nor is the darkness of the gear oil. I think your gears are shot, unfortunately.

 

[Dave LeGear]

Any metal is not good for that is a tiny magnet relative to the space it is trying to (help) protect. That oil also looks like it has been their a while (and getting overheated) unless it is picking up crud from the container is it landing in?

I would start shopping for a used or rebuilt lower unit that would fit that engine, don't think that one is going to last very long...

 

[Wilson]

Thanks guys, appreciate the input. I have a call in to the mechanic to come out and take a look. Waiting to hear back.

I’m leaning towards purchasing a new lower unit for my model from Crowley Marine. They have them in stock and for 2k (this includes tax and shipping) I can get a brand new genuine Yamaha unit and don’t have to worry about rebuilds. Plus I’m hopeful I can sell my old unit for parts on eBay for $500ish.

I find this to be the best/quickest way to get back on water. As much as I want to pull trigger on new motor I don’t have $8,000-$12,000 for something new plus in my area probably looking at a 3-6mo wait for this time of year.

Any advice would be greatly appreciated.

Thanks!

 

[dboyd351]

2k for a new OEM lower unit is a good deal and is likely your best bet for fixing that motor. Before you do that you might want to run a compression check on all your cylinders and have a sample of your engine oil analyzed to try and ensure the rest of the motor will last awhile.
Good luck.

 

[Wilson]

2k for a new OEM lower unit is a good deal and is likely your best bet for fixing that motor. Before you do that you might want to run a compression check on all your cylinders and have a sample of your engine oil analyzed to try and ensure the rest of the motor will last awhile.
Good luck.

Great advice, I will pass that along to the mechanic to have them check for those. A year ago compression was tested on the motor and tested really good. The oil on the other hand no clue except for routine oil changes and no one mentioning anything specific.

 

[Dave LeGear]

This one will help you save on some (future) wear and tear on that engine as long as she is not already worn out.

https://www.flatsnation.com/post/low-budget-outboard-pre-lube-pump-4-stroke-only

1. Most techs cannot pull a oil analysis, those have to be sent out to a lab (you can do that and should) on your oil to get a break down of metals, etc. suspended in that oil sample without (someone) reporting back otherwise. Just the facts ma'am as they say
   
2. While compression tests are good, leak down tests tell "the rest of the story" since they are also checking for valve sealing, etc. and not just condition of the rings. Engines can punch good compression while moving, that though is not a total picture of how the engine overall, is sealing.

Picture this... Any engine can run well fast since RPM speed, is helping in it doing just that. How (slow) one can run, is a much better indication of how tight she really is?

And shocking to most is that the purpose of the Rings is not to seal that cylinder per se. Their primary role is to transfer heat from that red hot piston to the block so they don't melt down... This is why using some Chevron Techron (what Yamaha relabels as Ring Free and charges more for it) is good way to help keep them from getting all carbon up and seize, then fail, in their intended design purpose...

Not that you can put metal back on anything without replacing it, but getting them clean again will go a long way in returning power short of a top end rebuild. The only downside is it can put a lot of carbon into the lube oil thus, I would not run more that 3 bottles of it in a row, without an oil change. You simply do not want all that hard carbon sand like crud running through the engine. It alone (why internal engine cleanliness is so important) is hard on those soft rod and main bearings!

Hope this helps

 

[Wilson]

This one will help you save on some (future) wear and tear on that engine as long as she is not already worn out.

https://www.flatsnation.com/post/low-budget-outboard-pre-lube-pump-4-stroke-only

1. Most techs cannot pull a oil analysis, those have to be sent out to a lab (you can do that and should) on your oil to get a break down of metals, etc. suspended in that oil sample without (someone) reporting back otherwise. Just the facts ma'am as they say
   
2. While compression tests are good, leak down tests tell "the rest of the story" since they are also checking for valve sealing, etc. and not just condition of the rings. Engines can punch good compression while moving, that though is not a total picture of how the engine overall, is sealing.

Picture this... Any engine can run well fast since RPM speed, is helping in it doing just that. How (slow) one can run, is a much better indication of how tight she really is?

And shocking to most is that the purpose of the Rings is not to seal that cylinder per se. Their primary role is to transfer heat from that red hot piston to the block so they don't melt down... This is why using some Chevron Techron (what Yamaha relabels as Ring Free and charges more for it) is good way to help keep them from getting all carbon up and seize, then fail, in their intended design purpose...

Not that you can put metal back on anything without replacing it, but getting them clean again will go a long way in returning power short of a top end rebuild. The only downside is it can put a lot of carbon into the lube oil thus, I would not run more that 3 bottles of it in a row, without an oil change. You simply do not want all that hard carbon sand like crud running through the engine. It alone (why internal engine cleanliness is so important) is hard on those soft rod and main bearings!

Hope this helps

This great info thank you for taking the time, I really appreciate it. I’m sure I’ll have follow up questions once I dig into this.

Just curious if you recommend a good place for sending engine oil sample? Are those sample kits from Amazon you mail in any good?

 

[Dave LeGear]

Are those sample kits from Amazon you mail in any good? (I have no experience with them yet)

If you find one that you like and gives a good level of measurements employed, let me know by sending the URL and I will be happy to take a look at it!

Best,
Dave

 

[Harper]

All my oil samples, truck, car, diesel tractor, and outboard are done here. https://www.blackstone-labs.com/engine-types/marine/

They will analyze engine oil, transmision, differentials, etc.