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Cruising RPM

T

tbrodes

Regular Contributor
"hey guys, I was wondering wha

"hey guys, I was wondering what you all cruise your inboard engines at.

I cruise my carbed 454's at 3000 RPM ~~20ish knots

Wheres your sweet spot? I'm still finding mine..."
 
"..."Where's your swee

"..."Where's your sweet spot?"

A combination of sound, feel, and your wallet's contents!

I cruise my Chrysler 360s at 2,500 and 20 mph. They seem to like that and, being in a Marinette 32 Sedan, the throttles are barely open--you couldn't slip a pencil in the gap between the butterflies and the carb wall!

Suggest you do what I did: Mark the throttle position where the throttle handles are at cruising speed using tape and a marker. Then, in the slip, put the throttles in that position (engines off!) and see how far open the butterflies are. Now, if you're close to opening those huge secondaries (I assume you have Quadrajet carbs) then you need to cruise at a lower throttle setting. If not, go for it!

Jeff"
 
"Hey Ted, with the price of fu

"Hey Ted, with the price of fuel climbing by the hour, I decided I want my engines (twin 454's) to run as efficient as possible. I have just orered a Twinscan GPH meter and Twinscan tach. I'm under the impression that I will be able to accurately determine my sweet spot under any conditions. I'm also thinking about an engine synchronizer. Anyone have any experince with this equipment?"
 
I have an engine synchronizer

I have an engine synchronizer which helps as I can keep them both running equally. I do not have a flow scan...I am thinking about installing one. How labor intensive are they to install?
 
The engine sync I had was the

The engine sync I had was the old Jusdon LED style . Back in August I switched to the swing needle type. Simple connections to the tach and you are done in about 30 minutes. The 3" size makes the needle easy to see and to adjust rpm for.

The floscan was a bit more involved but also easy to install. An inline sensor gets placed between the tank and the engine to meter fuel flow. Some wiring is needed to be run thru a few tight spaces but again it is not a difficult job. Everything is marked very well.
 
">>Anyone have any exp

">>Anyone have any experince with this equipment?<<
When I ordered my new boat the dealer talked me into the ELECTRONIC TWIN-ENGINE SYNCHRONIZATION and CRUISE control, I didn't really want it. Best option I ever ordered, it's really useful especially in rough water. The wife loves it too.

Chuckie"
 
synchronizer. They have been o

synchronizer. They have been ok for me.
I have found out that the weather plays 90% of what I'm going to do with my boat. I know where my sweet spot is but 8 out of 10 times I need to adjust the motors due to weather and tides.
I treat my boat like a Trawler now. 8-10 knots and the trim 100%. What I do is get the boat up to speed 20-21 with the the boat trimmed out and then pull back real slow to I get to 10 knots.
The boat stays trimmed. It has saved me hundreds of dollars in gas.
Seattle Puget Sound area is around $3.65 a gallon.

I was thinking of getting a 30 gal caddy and buy it from a street station and top off before boating. Any thoughts on that?
 
"Yea, the gas prices are getti

"Yea, the gas prices are getting steep in New England as well. I have done jerry cans on my dock...i have a few 8 gallons jugs that I fill up and throw into the boat before I go out...it helps me more psychologically than anything else...oh well...just keep selling lumber..."
 
"friends in boating,
My 9

"friends in boating,
My 91 Carver aft cabin with 330h.p. 454's likes to run at 3300-3500 r.p.m. and is real smooth there.Anything less than 3100 and she struggles.The real thing to me is the props.I am going to try a greater pitch sometime this summer to see as I do not know my w.o.t.,but if I could lower the rmp it would be nice.
So what I am saying Ted is that we all have different combo's, but I think anything lower than 3600 is ok, but will burn more fuel the deeper you push....Todd"
 
"Wheew! Lots of questions her

"Wheew! Lots of questions here. I'll try to answer them all:

1. If your boat is struggling at 3,300 rpms, do NOT add any pitch! The poor motors are working very hard already.

2. My 'technique' for measuring the throttle positions works with any carb or EFI set up.

3. A FloScan unit will pay for itself in short order. Trust e on this (and if you have any install problems, let me know).

4. On fueling your boat at the slip, most marinas frown on that after several horrendous fires caused by spillage. Mine won't allow it at all.

5. gastite (what a handle!) is spot on; the only way to find 'today's' sweet spot is with flow meters. Wind, current, load (passengers and 'stuff') all make a difference. A good helmsperson will try different trim tab (outdrive) settings and throttle settings to determine the best MPG at that moment. With gas prices what they are we need to be smart as possible here! Agreed?

Fast--but economical as possible--Jeff"
 
Im saving my nickles to by a f

Im saving my nickles to by a floscan for my duel 350's. On a 30ft express I usually cruise between 2100 and 2500 rpm depending on the sea conditions. Respectively 16 to 21 knots on my gps.The boat likes this rpm range.
 
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