New props

[dogdoc]

Looking to put new props on my engines. 250hp ox66 on a 280 marlin. Not looking for anything special. Almost exclusively run 1 hour at 3800 rpm/30 mph to fishing grounds then troll for awhile and come home at 3800/30. At a loss as to what to pick, to many options

 

[glacierbaze]

Anytime you can cruise at 30 in the ocean, you’re doing pretty well. What are you looking for, higher cruise, better economy, higher top end?
And what props are you running now?

 

[Hookup1]

Yes...sounds like you are doing well. What is the problem you are tying to solve?

 

[DennisG01]

Agree - based on what you said, it sounds like you're doing good and don't need to do anything. Put that money towards fuel.

 

[dogdoc]

I have a vibration in the 1300-1400 rpm range. Have ruled out other causes and feel it is the props

 

[DennisG01]

I have a vibration in the 1300-1400 rpm range. Have ruled out other causes and feel it is the props

OK, well that's different. any other information you "forgot" to mention?

However, are you sure it's not just the normal OX66 cylinder deactivation/activation feature you're feeling?

It wouldn't hurt to have the props sent out to be tuned, though. It's a good idea to do that once in a while, anyway. And it's a whole lot cheaper than new props.

 

[dogdoc]

brought the the props in for tune up. shop took one look and said yup you need it. guy thought the vibration was from loss of cupping and cavitation secondarily from running props in sand at bars and shallow spots. one hub was shot from dry rot. question how often do you check the hubs?

 

[DennisG01]

question how often do you check the hubs?

When I start to hear/feel slipping It's noticeable - RPM's start to spike without "bite" in the water. A lot like a manual car where you're travelling at a certain speed with the throttle at, say, 30%... then slightly depress the clutch. Since you're getting them tuned, replacing the hub is a good idea - but normally, other than looking at the hub once a year when I remove the prop to grease the shaft, I don't worry about it until there's a problem or the hub looks noticeably bad - then I'll have it re-hubbed as a preventative measure. But, to answer your question more directly... looking at it once a year is plenty.

 

[seasick]

The original hubs are kind of potted in place ( like glued with a sealant) and can get out of alignment but not spin. I have had that occur on my SWS prop.
One thing you didn't make clear is if the vibration occurs on one or both motors. To tell you have to run on one motor at a time.
Also it would help to know what the vibration is like. For example, an out of balance prop will often be felt by you feet on the deck whereas a motor issue may be seen by looking at the motor shake.
You can also try running the motors in neutral to about the revs you feel the vibration. If you still feel the vibration, it is probably not the prop(s).
You may need to check the prop shaft for runout or play.

Now for my funny story. I had my props tuned on Myotherboat a few years ago. They were Merc props with Flo Torque hubs. After the tuneup and new hubs, the hull made more speed at a given engine rev setting. Sounds good but the down side is that I was no longer able to create a no wake state without shifting in and out of gear

 

[glacierbaze]

If there is a casting mark, or any distinctive mark on the hub, or the prop housing, make an aligning mark in the other piece. If no mark, then mark both. You can look at them anytime, and say yes or no to prop slip.
Don't know if materials or methods have changed, but in 40 years, I may have had 3 props re-hubbed.

Seasick, did you try tilting the motors pretty high up, or run on one, to slow the speed at idle

 

[seasick]

If there is a casting mark, or any distinctive mark on the hub, or the prop housing, make an aligning mark in the other piece. If no mark, then mark both. You can look at them anytime, and say yes or no to prop slip.
Don't know it materials or methods have changed, but in 40 years, I may have had 3 props re-hubbed.

Seasick, did you try tilting the motors pretty high up, or run on one, to slow the speed at idle

I did not tilt up the motors up high but I do often run one motor through the no wake areas.

One point I would like to make about spun hubs is that there are hubs that spin under load where the bushing slips in the casting. Those are pretty easy to identify by applying throttle and thrust quickly and watching how fast and how high the revs go. In one case, I had hit a submerged log and the hub spun a few degrees but then stayed in that position. It wasn't obvious to me that the hub moved and there was no slipping under load. The hub was just a tad off center causing a vibration at lower revs. The prop shop knew immediately that my hub had shifted. That's why they are the prop people

 

[dogdoc]

no vibration in neutral
port much worse than starboard so bad vibrated of trim skeg on lower unit
followup next week when props back

 

[seasick]

no vibration in neutral
port much worse than starboard so bad vibrated of trim skeg on lower unit
followup next week when props back

good luck. let us know how it works out.

 

[dogdoc]

got the props yesterday. starboard prop went on no problems. port prop a different story. prop went on fine but spacer just would not drop in. fussed with it for quite a bit and got it to sit on the splines but not slide in, so put on the nut and slowly pressed it on. before i did that, to be sure it was not the spacer i easily could have used either on the starboard engine. as i recall that prop was hard to get off actually had to knock it from the front with a piece of wood. when spinning the starboard prop it spins smooth and for twice as long as the port. spinning the port prop i hear a faint rubbing noise and does not spin as freely or long as starboard. i cannot see any wobble in the shaft when spinning the prop. have not put boat in water yet, will do that tomorrow

 

[DennisG01]

Could be something (fishing line?) that got into the shaft seals and is causing that sound. Check gearcase fluid for water contamination as well as closely inspecting the seal that you can say.

Inspect the splines closely for damage. Possibly file gently.

 

[seasick]

You should measure the run out of the prop shaft as well as the play. That will eliminate a bent shaft and a worn bearing.
The difference in drag between the motors doesn't mean much if anything. There is often more drag in a CCW gearbox. Of course if there is a very large difference that's a different story.
I woulkdn't file the splines butI would clean them with something like brake cleaner, inspect for nicks or burrs and maybe sand with fairly fine sand paper.
When reinstalling the prop, use a little bit of grease smeared all over the splines. It also helps to use a torque wrench when reinstalling. Some hubs require a lot of torque.

 

[dogdoc]

Ran to the travel lift to pull boat. Vibration is much better, seems normal now. Bad news is metal shavings in the gear lube of port engine. Thats the one that spun less and made a faint noise. Mechanic brought the lower units home to check them out.

 

[seasick]

Ran to the travel lift to pull boat. Vibration is much better, seems normal now. Bad news is metal shavings in the gear lube of port engine. Thats the one that spun less and made a faint noise. Mechanic brought the lower units home to check them out.

Some fine metal filings are not abnormal. Chunks on the other hand are a bad sign
Since the port LU is probably a counter rotation , as i mentioned, it has more drag and that may explain some filings. When you last changed its oil, did you see any filings?
How does the port motor shift lever feel recently. Has it gotten stiffer?

I can not explain why your vibration would go away. That doesn't make sense unless something was wrapped around a prop. When you had the vibration, I assume you raised the motors to see if the props were fouled.
Of course, if a hub shifted a bit and that made the prop vibrate, that hub could have shifted again, possibly making the prop less imbalanced. You still need to have the props checked out or at least the prop hubs.

 

[dogdoc]

props were serviced, new hubs, balance and recupped. that made the vibration go away. i would say the metal was more on the chunk side but some fine too. matter of fact that motor has become very hard to shift!

 

[seasick]

props were serviced, new hubs, balance and recupped. that made the vibration go away. i would say the metal was more on the chunk side but some fine too. matter of fact that motor has become very hard to shift!

Somewhere along the way, I missed the fact that the props were serviced. So that explains the vibration.

With regard to the hard shifting, I asked because that might the metal in the LU oil. In one scenario, there is a problem in the LU itself but I am not convinced yet. The second is that because shifting is hard to do, you may be doing some more CHUNK-CHUNK-CHUNK when shifting that motor as opposed to a relatively single CLUNK as the dog clutch engages. If you can try shifting in and out of gear and compare the effort and clunking sounds between the two motors
You may be able to check by disconnecting the shift cable at the motor end and manually shifting in and out of gear using a wrench or channel lock or the like. You can also try moving the control in and out of neutral to see if you can tell that the cable may be binding. Note that you may find that you can only shift either in and out of forward or only in and out of reverse. That is normal for the motors. They typically don't like and shouldn't be shifted in and out of gear unless the motor is running but by manually turning the prop and shifting, you can usually get the gears lined up.