Importance of keeping RPM matched on twin engines
 

We are now the proud owners of our first twin screw boat. A 2005 Fountain Fever 32. I'm just curios how important it is to keep the rpm on both engines matched. It seems like one is always 100 - 200 off. I find myself constantly looking at the tachs and adjusting. Not owning a twin before I never considered what it would be like to drive one at speed. Now that I have it seems strange that there isn't some automated system to keep the R's matched.

I know some cruisers have RPM matching systems. The first thing you should do is verify your tach readings then verify your trim indicator settings. I would not be too concerned about a 100rpm but it is a few MPH difference between the two.

Great question. but with all things being equal (tune no codes in system) You have to remember like I did at first that they are two separate running systems.

My starboard motor was behind 100 rpm with even sticks and a slight palm adjust at 3200 rpm synced in two easy. You can hear the sound change as they harmonize .

Have your throttle cables checked and adjusted as well and you will be just fine.

Enjoy your new 32

This ^^^, gauges have a certain accuracy, or "error". They may not be that accurate, (i.e., could actually be running the same RPM, but show two different readings.)

yep, your ear is the best tool here. After you get use to the boat you will develop a feel for the sound, you'll hear the harmonics go out of phase. As for importance it is more of an efficiency thing, you wont hurt anything or cause any ill handling characteristics running out of phase in normal operation and as you learn the boat it will eventually be more of an automatic thing. You sort of develop a way of holding the tops of the throttles and twist them in order to keep them synced, if they are drastically different adjust cables accordingly.

You know whats a super fantastic fun time?
Adjusting (4) 4 barrels so not only the secondaries all open at the same time between carbs but at the same time between motors. Oh yeah good times :D

Like they said, you will definitely get a sense from the sound when they are in synch! Nothing better than hearing two big blocks humming in tune!

As you sync them in, you will hear the "throb" go away to one single roar of the engines. For me there is nothing more accurate than the sound (over sync meters, tachs). I wince when I see a big cruiser going by, engines throbbing away with the captain completely unaware the engines are out of sync.

Wow, great advice! Just what I needed. Thanks so much.

Another point is trim position. We all know as you begin to trim out efficiency increases. Your trim indicators may be off therefore one engine/drive is running less efficient. You can bump the sticks to sync rpm but that doesn't mean the drives are in sync. My port drive takes two "taps" to get it in sync. I have a bad position sensor so I know that when I raise them together I have to tap twice to bring them level.

Just another thought to add to the mix.