CONTINUOUSWAVE

I have a 2004 190 Nantucket with the original Mercury OptiMax 135 engine.

I believe that the propeller—size unknown—is as installed by Boston Whaler and is a stainless steel Mercury propeller.

[The engine] has a bit of a vibration at certain engine speeds—nothing major but I notice it.

The propeller has no visible, obvious damage. It has 180 hours of use.

Q1: do you recommend replacing the propeller?

Q2: do you recommend sending out the propeller for reconditioning and balancing?

Thanks

—Mike

Where are you located?

If boating season is going to end soon, unless vibration is horrible, run [the engine] and then send out [the propeller] in the off season.

Propellers usually do not go out of balance. I have literally ripped off half a blade and you would hardly notice it. I would mark the center of the propeller shaft with a color and then spin the prop and see if shaft is bent. You can do that at a sandbar or on the trailer.

i keep my boat in MIlton Harbor (Westchester county) New York.

The vibration is not that bad.

I will probably take care of it after I haul the boat out at the end of October.

Your expectations for a Mercury OptiMax to operate without any vibration are probably too high.

To test your hypothesis that the vibrations are due to the propeller, remove the propeller and run the engine at various engine speeds. Observer any change in vibration.

If the 135-HP OptiMax engine still vibrates, the cause is not the propeller.

It may be time to have your prop worked and balanced.

Your propeller is probably not damaged or out of balance, and the lower unit probably does not have a bent shaft. Propeller imbalance and bent shaft forces and vibration increase in amplitude exponentially with RPM increase. You would know as the engine speed increased and the condition got notably worse--even with the change in hydro-dynamic loading--kinda like a flat tire on a car. It's rather obvious the condition worsens with speed.

What vibrates? The entire boat? Just the engine (as stated)? Or something else?

I don't doubt you have something annoying, but something wrong, hard to assess in a few words.

There are likely a few resonant speed bands that as mounts and isolators wear out become more prominent; or something could be wrong mechanically--but these would likely affect a whole RPM range.

Quick video:

https://www.youtube.com/watch?v=xXSHCYe ... e=youtu.be

It's probably nothing.

Q3: Is the vibration when the camera is shaking? That is not the prop if so.

Q4: Does it feel like it is dropping a cylinder when that happens?

I have to admit that is a wild video, but it may just be nothing. Show that video to a Mercury mechanic.
--Archie

I do not think that vibration is being caused by an off balanced propeller - that does seem like the engine is dropping a cylinder. As recommended, a Mercury mechanic should do a diagnostic on the engine.

A method used by shade tree mechanics since the invention of spark plug fired engines to detect a misfiring cylinder is--one cylinder at a time--to remove a spark plug cable and reinstall it until find the cylinder that causes no change in the engine idle speed. If the idle speed does not change the misfiring cylinder has been detected.

The three most probable causes of a misfiring cylinder are:

-- a faulty of fouled spark plug,
--a faulty spark plug cable, or
--a faulty fuel injector in the case of a fuel injected engine.

Spark plug cables are easy to test and replace and spark plugs are easy to replace. If the spark plugs and cables are not causing a misfire I agree that it's time to seek professional help.

One caution: when removing the spark plug lead from a spark plug on a modern engine while running, having some path for the spark energy to find ground is a good precaution. If the spark voltage generated for that cylinder has no path to ground, it may find its own way to ground, perhaps by breaking down insulation in the spark coil. Test procedures usually recommend connecting the spark leads to a resistor loading device to dissipate the electrical charge. Check the service manual for your engine for advice.

I think a better better way to verify spark voltage and spark plug firing in individual cylinders is to use an in-line spark gap tester.

To use an in-line spark gap tester, the spark gap tester is inserted into the spark plug wire at the spark plug. The engine is started with the cowling still removed. Visually observe the spark gap in the in-line spark gap tester, looking for a steady arc across the gap corresponding to the periodicity of that cylinder firing. If the spark voltage is strong it will fire across the gap in the in-line tester and the gap in the plug.

An in-line spark gap tester that I have used to perform diagnostic testing on individual cylinder spark firing with excellent results is a model 20610 LISLE In-line Ignition Spark Tester, pictured below.


Fig. 1. An in-line spark gap tester made by LISLE and widely available.

LISLE products are sold everywhere.

The behavior of the engine does not sound like or feel like a cylinder misfire. A mechanic will take the boat on a sea trial next week.

I certainly agree the best way to check spark plugs is with the proper tool. However, it's not a bad thing to know some "field expedient" methods for those days when you can't lay your hands on a seldom used tool.

Admittedly, I learned the old method in 1953 after buying my first car at age 13, a $35 (two weeks wages) 1931 Ford Model A coupe. If anyone has fooled around with the spark plug conductors, lengths of uninsulated flat copper strap, they won't forget the jolt of electricity delivered by a Model A coil. I learned a lot about cars with that Model A.

BUTCH--Automobile engines in the 1930's had no transistors.

Outboard engines in 2019 use millions of transistors.

Jim - Again, I certainly agree. That is one of the reasons I no longer work on engines. Physical ability may be another factor. Removing the engine cowling from our 135 HP Verado to check the crankcase oil level is quite a chore. I doubt I could do it while afloat even in calm conditions, perhaps standing on the bottom in very shallow water I could manage it.

Quick update:

Had a Mercury Optimax specialist have a look. He gave my engine a clean bill of health.

While he had the cowling off, he recommended to replace the auxiliary oil reservoir and the air pump's air filter. These items are unrelated to the thread's topic but figure I'd mention nevertheless.

Will still proceed with prop balancing this winter.

My engine's at about 191 hours; I suspect I'll hit 200 hours before I pull it out of the water in a few weeks. In the Spring, I'll have a 100 hour service performed. I may do coils and ignition wires as a preventative (despite the low hours).

Will provide an update about the prop balance before / after in early May.

Thanks!

Again, I have never heard of balancing a prop.

https://www.youtube.com/watch?v=ghWhcI6cjI8

https://www.youtube.com/watch?v=rPxYBbqFDxE

videos about balancing boat props.

When you have a prop repaired they always balance it after the repair. It is a normal part of the repair. A unbalanced prop could create vibration frequencies at different RPM. A bent blade can also make vibrations and a bent blade might not be noticeable by the naked eye.

An aluminum prop is much ligher and will probably not cause noticeable vibrations being damaged. An aluminum prop missing part of the prop is not nearly as bad as a stainless steel prop out of balance.

I too once had an aluminum prop that had part of the blade missing and didnt even notice it.

Another time, I had a part of an aluminum prop break off and when idling the outboard vibrated bad. I could not rev up the engine with out destroying the engine. I had to put spare on in the water. It was the only way to get back to the launch. And was afraid I might drop the nut, pin, tools or prop in the water. I wore a life vest.

The vibration on your Whaler with the Merc may just be crankshaft harmonics that just like to vibrate at certain RPM.
Archie

Yes I agree that they can fix a prop but it is not like they put wheel weights on it like a rim or weights on a ceiling fan.

Yes changing a prop in the water sucks.

biggiefl watch the videos if you want to learn how props are balanced.

When you are welding repairs and grinding them there is no way to know if the blades are balanced by just looking at it. You put it on a balancer and remove metal from the back of the prop until it is balanced.

Tell me the best shops for propeller balancing.

I'm happy to mail away.

Henry H. Smith in Algonac, Michigan repairs propellers for outboard engines.

General Propeller in Bradenton, FL is one of the largest shops in the country. Google or look in most boating mags for more info.

biggiefl wrote:General Propeller in Bradenton, FL is one of the largest shops in the country. Google or look in most boating mags for more info.

Thanks. Looks like a highly-specialized shop. Have requested a quote.

https://henryhsmith.com/

They have been in the propeller service business for 119-years. There are probably more boats in Michigan, Ohio, and Ontario than in Florida. Every outboard dealer in this area sends propellers to them for repair.

Jim they are international and specialize in LARGE propellers. It is nice that they cater to locals as well. As far as boat population goes I am certain that the Miami and Ft Lauderdale boat shows are 2 of the largest in the world(Ft Lauderdale being #1). Your Mid America(Ohio) comes in around #13 with no others in the Midwest on the list.

http://baumannprops.com/ this is best propeller shop in Texas and they ship. They will want to know many details about the boat and what you are wanting to accomplish performance wise.
Archie