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View Full Version : Boat Break-in & Running Q's

thinkxingu
10-11-2015, 12:04 PM
It's early, but we just ordered a new tritoon for spring delivery, which will be our first new boat. It's a Mercury 150 OB, so: 1. What is the modern break-in approach and 2. Does running an engine at WOT hurt it (after break-in)?

Thanks!

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noreast
10-11-2015, 01:05 PM
Cliff notes answer is to vary RPM's during break in period. Running wide open will not harm motor after break in. These motors are made to take a beating. RPM's wide open will probably be between 5,400 and 5,800 depending on prop selection, which the dealer will take care of with your input as how you plan to use and load the boat.
Slickcraft
10-11-2015, 03:07 PM
Yes vary the RPM in the break in. Our new Yamaha 4 stroke specified 10 hour break in with operating at a range of speeds and WOT limited to 3 min at a time during break in. After that no speed restrictions whatsoever.
DesertDweller
10-11-2015, 03:50 PM
As the others have said the important thing is to vary the RPM's during the break in period (10 hours). Most manufacturers have RPM limits during the first few hours so be sure to read the owners manual for the specifics. After the break in period do what you want but usually you will find a comfortable cruising speed at an RPM much less than wide open.
thinkxingu
10-11-2015, 04:53 PM
Sounds good, all. So running the engine at a high RPM for long periods of time (after break-in) doesn't hurt it? I guess I'm so used to a car engine cruising at 1800-2000.

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noreast
10-11-2015, 05:21 PM
Won't hurt it at all. You'll probably find you won't do it often, Usually my passengers think were flying at 20mph. Good to have the power for when you need it. On a calm day, on a tri-toon, on Winnie running at 40mph, what a feeling, smooth as silk.:)
8gv
10-11-2015, 06:53 PM
Sounds good, all. So running the engine at a high RPM for long periods of time (after break-in) doesn't hurt it?

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W.O.T. operations are ok...

IF THE MOTOR IS EQUIPPED WITH THE CORRECT PROP FOR THE LOAD.

As mentioned above, achieving the recommended maximum rpm at W.O.T. matters!
thinkxingu
10-11-2015, 07:02 PM
Since the motor comes with a stainless prop from Harris, can I assume it's the right one for the boat? If I'm not mistaken, the parent company of Harris owns Mercury, and they often do their testing on Harris boats.

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Dad sold the C * C
10-11-2015, 07:09 PM
Just went thru the break in of the 150 4 stroke Merc this summer. It's a 20 hour break in with varying the RPM, the Manuel says to run it at WOT during this period but for 2 minutes or less at a time. Apparently this engine will beep at you if you do something it doesn't like during break in..

It was running real nice just before I put it to bed for the winter.
pjard
10-11-2015, 07:30 PM
A bit off topic but my 115 Mercury will run about 6200 RPM's at full throttle. That equates to 413 RP Second....it's amazing to think about it. It boggles my mind that thing doesn't just explode! What a machine!
FWP
10-11-2015, 07:31 PM
Since the motor comes with a stainless prop from Harris, can I assume it's the right one for the boat? If I'm not mistaken, the parent company of Harris owns Mercury, and they often do their testing on Harris boats.

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never assume its the right one,one new boat that I bought had the wrong pitch on the prop. lake testing on the computer proved that fact

:D
thinkxingu
10-11-2015, 07:46 PM
never assume its the right one,one new boat that I bought had the wrong pitch on the prop. lake testing on the computer proved that fact

:D
How does one decide on/figure out the right one?

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8gv
10-11-2015, 08:20 PM
Determine the manufacturer's maximum rpm range.

It should be in the owner's manual or placarded on the motor.

Load boat with typical weight you expect to carry and full fuel.

In a perfect world with a perfectly pitched prop, you should hit about the middle of the rpm range.

Be aware that with a lighter load, you will get higher rpms. Don't over rev it!

One inch of increase prop pitch will decrease the rpms by about 200.

Changing the prop diameter and number of blades can affect the max rpm as well.
8gv
10-11-2015, 08:22 PM
Your boat dealer should verify that the motor gets proper rpm at W.O.T.. If it doesn't, ask for an appropriate prop to be installed at no charge to you.
Resident 2B
10-11-2015, 09:28 PM
A bit off topic but my 115 Mercury will run about 6200 RPM's at full throttle. That equates to 413 RP Second....it's amazing to think about it. It boggles my mind that thing doesn't just explode! What a machine!

I believe it is 103.33 RPS. Still a lot.

R2B
thinkxingu
10-12-2015, 04:40 AM
In a perfect world with a perfectly pitched prop, you should hit about the middle of the rpm range.

You lost me here--don't I want to base the prop on RPM peak?

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8gv
10-12-2015, 07:35 AM
Considering this is a pontoon which may have different performance characteristics than the boat hulls with which I am familiar, there may be better advice available.

This may be a matter of opinion / personal preference. Here's mine:

Consider that the boat will perform quite well at the middle of the rpm range and somewhat better at the top of the range.

You are setting it up for your typical load. If you target the middle of the range and occasionally carry extra weight the motor will still achieve the bottom of the rpm range at W.O.T..

If you go out lightly loaded, you will hit the top of the rpm range and won't have to reduce throttle to keep from exceeding it.

It would be interesting to hear the experiences of other 'toon owners here.
ishoot308
10-12-2015, 07:40 AM
You lost me here--don't I want to base the prop on RPM peak?

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Not to butt in here, but with an outboard and especially with a pontoon boat, you want to be as close to the engines specified MAX rpm (just before rev limiter kicks in) as you can with you alone on the boat and half tank of gas. This will ensure your engine is working as efficiently as possible when loaded down.

Dan
SAMIAM
10-12-2015, 08:30 AM
All above is accurate but my dealer told me to avoid prolonged periods at idle speed on my new Merc Verado 4 cycle. Varied speed, brief bursts of WOT are all good.....just no 2 hour booze cruises during break in.
noreast
10-12-2015, 02:31 PM
You won't have a problem with your prop, They are a very good marina, They will get it right. I have 2 props, one for cruising, one for water sports. If your left on your own it can be extremely frustrating.
Dave R
10-13-2015, 03:10 PM
A bit off topic but my 115 Mercury will run about 6200 RPM's at full throttle. That equates to 413 RP Second....it's amazing to think about it. It boggles my mind that thing doesn't just explode! What a machine!

It's all about piston speed (the distance the piston travels over time, or the stroke in feet x 2 x RPM). Most marine engines are designed to run at 3000 feet per minute of mean piston speed. High-performance street engines typically run up to 4000 FPM. Racing engines run way over 5000. Stroke and RPM are the key components to piston speed, the shorter the stroke, the higher the RPM can be for give piston speed. The engine in my motorcycle has a 4000 FPM piston speed at 12,000 RPM. It'll do that all day. My boat would hit 4000 FPM at only 6000 RPM and it would not last long doing that (if it were even possible).
LIforrelaxin
10-13-2015, 05:08 PM
1. Don't assume your boat will come with the right prop....
2. Talk with the dealer about your planned usage...
3. Find others with the same boat and engine and see what they have found

Now as for the advice thats been given here..... listen to ishoot, Dan has had many Pontoons......

Once you load the boat up, all the WOT specs etc. go out the window... Fully loaded you should expect to be at the lower end of the WOT spec.... moderately load you should be up towards the higher end of the Spec.....