Help--Need quick answer about cruising speed

Swimparent

Swimparent

New Member
Dec 16, 2009
65
Lake Guntersville, Alabama
Boat Info
300 Sundancer; Lowe 220 Sport Deck with Mercury 150 Outboard; Yamaha FX140 WaveRunner
Engines
Twin 5.7L MerCruisers w/ V-drives
I posted the following in the "Newbie" forum, but I need a really quick answer as we are leaving in about 1/2 hour.

I need a quick answer as to "normal" cruising speed---mph and rpm----for a 1995 300 Sundancer with twin Mercruisers with V drive? We are "test driving" again today.

Thanks.
 
What kind of engines? I would shoot for 3250 RPM if they are V-8's and 3500 if they are V-6's. These are complete guesses. The V-8's would probably get you almost 30 mph and the V-6's about 25 mph. Remember - you wanted a quick answer, not necessarily a perfect one. Anyone have some better gouge?
 
Hey John,
Thank you so much for the information. We ended up buying the boat & my husband was happy with the way the boat performed today knowing that it had 3 year old gas and needed an engine tune-up.

On another note....we have a home at Mexico Beach and my brother in law is in Port St. Joe. Small world! We also have a friend who is a vet at PCB and keeps his boat at Captain Dave's. I am going to file your name away in case we ever actually go on the trip from Lake Guntersville to the beach house :)

Thanks again for your help!

Anne
 
Thanks,
We are excited. A few projects to do before the start of boating season which comes right after April 15 at our house! Guess what we both do for a living? :) Well he does, I am "retired."
 
Swimparent said:
I posted the following in the "Newbie" forum, but I need a really quick answer as we are leaving in about 1/2 hour.

I need a quick answer as to "normal" cruising speed---mph and rpm----for a 1995 300 Sundancer with twin Mercruisers with V drive? We are "test driving" again today.

Thanks.
Click to expand...


From one newbie to another....WELCOME :thumbsup:
 
This is the boat. I have tried to put it in my profile, but no luck yet. Well maybe it did....when I preview looks like it is there.
 
Swimparent said:
This is the boat. I have tried to put it in my profile, but no luck yet. Well maybe it did....when I preview looks like it is there.
Click to expand...

Beautiful sleek lines......:smt001
 
Swimparent said:
Hey John,
Thank you so much for the information. We ended up buying the boat & my husband was happy with the way the boat performed today knowing that it had 3 year old gas and needed an engine tune-up.

On another note....we have a home at Mexico Beach and my brother in law is in Port St. Joe. Small world! We also have a friend who is a vet at PCB and keeps his boat at Captain Dave's. I am going to file your name away in case we ever actually go on the trip from Lake Guntersville to the beach house :)

Thanks again for your help!
Anne
Click to expand...

To bad it's a 30 footer.... I would tell you to come on down to lake Martin.... But nothing over 29' allowed :huh:
 
MWPH---I guess we will bring it up at the beginning of the week. The mechanic at Goosepond is out of town for the holiday and I think we will take her straight there for repairs.

Spookeay--You just answered a question for me. We were down at a friend's house last summer and I noticed there were no "big" boats. My hubby thought it was because there was no outlet to be able to travel long distances, thus no need for boats large enough to live on for a while. It is an absolutely beautiful lake though. It was so clear off of the dock you could watch the fish as they nibbled at your legs :)
 
She looks so beautiful... sitting like that in the water... I'm jealous... and I think I'm about to cry:smt089
 
There is not a true definition of cruising speed. Cruising speed is the definition that you prefer.

There is the cruising speed where your boat is barely on a plane, where your planing MPG efficiency is maximized. There is also your cruising speed where you are running at a percentage of maximum horsepower.

All you need is a fuel meter and a GPS to determine your efficiency in MPG. I plotted a curve on paper to determine my efficiency at a given RPM. RPM vs GPM
 
Spookeay--You just answered a question for me. We were down at a friend's house last summer and I noticed there were no "big" boats. My hubby thought it was because there was no outlet to be able to travel long distances, thus no need for boats large enough to live on for a while. It is an absolutely beautiful lake though. It was so clear off of the dock you could watch the fish as they nibbled at your legs :)
Click to expand...

Yes, It's the 3 lake ban here in Alabama. Big Big hoop-La over the last year about it. It was struck down on appeal.
So. Nothing over 29' long. Nothing over 26' that can go over 60 MPH and no houseboats.. Some types got grandfathered but the go fast boats had to go,. No and if's or buts .
Lots of people PO-ed and can't get rid of there boats becasue they owe more than they can get.

Such is life I guess.:smt101
 
Congratulations on your purchase! That certainly looks like a fine boat you got! Hope you enjoy it!

Four Suns is correct in my view. I believe "when the MPG is maximized" and "Where the boat is barely on plane" are slightly different. I am not sure if Dave's original post, however, has a minor punctuation problem which is generating confusion.

My boat will be "barely on plane" at about 25-27 MPH, but really doesn't seem to run well there. I never did a MPG analysis, but the ride is definately a bit rough. Go through a wake incorrectly, and the boat starts to bog down. I generally bump up the throttles slightly and the "cruise" at about 30mph/3000ish RPM. These numbers, however, are VERY boat specific and totally inapplicable to your boat.

The real measure of boat health is running WOT - Wide Open Throttle. From the Sea Ray website, you can get information regarding information specific to your boat regarding what RPM the engines should be running when you go all out. If the boat fails to reach maximum RPM. . .then the trouble shooting begins! On my boat, failure to reach W.O.T. usually means bottom growth issues. Too high RPM at W.O.T. usually means incorrect props. Overheating at W.O.T. is an engine issue (generally in the cooling system). These are all, of course, generalities.

In my view, running W.O.T. is like a cardiac stress test. Good to do it every once in a while to make sure everything is ok. . .but you don't do one every day. I generally run W.O.T. about once a month for a few minutes. Mostly because it is fun :) There was a recent thread on this topic elsewhere in the forum.

It sounds like your boat has I/O drives. If you have three year old gas in the boat, that probably means the raw water impellers are also at LEAST three years old. I would consider replacing these at this time.
 
Four Suns said:
A planing hull/engine combo generally does not have MPG maximized when it is barely on plane.
Click to expand...

Not in my experience with planing vessels. After on a plane, the Speed vs MPG curve increases at an increasing rate. It does not decrease after a vessel is on a plane. In fact it is true that in order to double the speed of a vessel, you must anywhere from a squared to a cubed relationship increase the horsepower. Off a plane, the MPG is much better, but this is not what I am talking about.
 
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