Newbie Questions... Basic Stuff

[davemoore]

Newbie here... these may be dumb questions, but how else do I learn?

Boat: 1983 - 18' Marlin with Mercruiser I/O...

#1: What is the rule of thumb about running the motor with the outdrive up (trailer position)? Should it NEVER be done? I noticed that when I had it running with the unit up, at about 1500 RPM there was a really loud "rattling" noise in the upper unit, but when it's down, it wasn't there. Of course, I had the control in neutral. With the drive down, no matter what RPM's (800 - 4000), the outdrive is quiet.

#2: While in the water, how many degrees does the outdrive move when you trim up? I assume all the way down is 0 degrees. I don't know the answer to this because my trim switch doesn't work, but from what I've read it seems like it's FAR less than when you "trailer" the outdrive.

Thanks,
Dave

 

[5150abf]

Re: Newbie Questions... Basic Stuff

Ya, that has a drive shaft just like a car and if you get too much angle on it you bind the U joint so I wouldn't run that in gear with it tilted up.

Without a trim gauge you will just have to geuss where it is which isn't hard to do once you get used to it.

When you start out the drive should be all the way down and as you accelerate raise it uplittle bits as you go faster when the boat is planing nicely stop.

There will come a point when raising the drive any more won't do anything, you just need to do and it get a feel for it.

 

[_chris_]

Re: Newbie Questions... Basic Stuff

Ya, that has a drive shaft just like a car and if you get too much angle on it you bind the U joint so I wouldn't run that in gear with it tilted up.

Without a trim gauge you will just have to geuss where it is which isn't hard to do once you get used to it.

When you start out the drive should be all the way down and as you accelerate raise it uplittle bits as you go faster when the boat is planing nicely stop.

There will come a point when raising the drive any more won't do anything, you just need to do and it get a feel for it.

What is the benefit of raising it as you go faster? I have always just left it all the way down.

 

[5150abf]

Re: Newbie Questions... Basic Stuff

It gets the bow up out of the water and helps the boat run much faster.

The thrust of the prop comes straight off the prop so if you leave your drive all the way down the thrust is actually pushing the bow(front) down so you are plowing through the water.

As you trim up the the prop is now pushing at a positive angle and lifts the bow making the boat go faster, so you probably 10-15 mph you didn't kniow about.

 

[Jeep Man]

Re: Newbie Questions... Basic Stuff

I assume you are not running the motor when it's out of the water and no muffs and water hose attached.

 

[davemoore]

Re: Newbie Questions... Basic Stuff

Oh no, I put the muffs and hose on everytime I run it in my driveway... don't want to damage the impeller...

 

[26aftcab454]

Re: Newbie Questions... Basic Stuff

once you start trimming the motor out to lift the bow- and find a sweet spot- if you trim too far out the bow will porpise up and down- then trim back in until it stops.
BTW trim gages are cheap and easy to install.
It is better to ask dumb questions than make dumb mi$take$. thats why we have these forums- you will find a weath of boating knowlage.

 

[anon1]

Re: Newbie Questions... Basic Stuff

Ya, that has a drive shaft just like a car and if you get too much angle on it you bind the U joint so I wouldn't run that in gear with it tilted up.
...

I wouldn't *ever* run that with it tilted up, in gear or not.

I think that the driveshaft turns all of the time that the engine is running. I think that when you shift it into gear it actually does the shifting in the very lower part of the stern drive.

 

[davemoore]

Re: Newbie Questions... Basic Stuff

Anon1 - you are absolutely correct. I will not ever run the motor again, unless the drive is all the way down. It's putting stress on the u-joints.

I finally got a service manual for the Mercruiser drive, and it has a cut-away picture of the outdrive... you are correct. The shifting is in the bottom.

Thanks for the replies...

 

[madurodave]

Re: Newbie Questions... Basic Stuff

I just learned from this thread. No dumb questions is right!