Fuel efficiency

[tsawyer]

I can live with the reality as long as it appears to be just that.

I was concerned that I really should be getting better than .35 mpg.

I still think I should be able to get at least .5 mpg.

That said, I am cancelling my planned Abaco trip. I think 350 miles round trip at .35 mpg and gas near $6.50 equates to almots $7k in fuel costs.

I had planned on it being somewhere closer to $4k.

I'm going to look into some of these ideas (trim tab upgrade, etc) and see what I can do to make it work better.

If my wife were a big girl, I'd put her up on the bow. But she isn't, so I'll have to find other solutions.

[captainmaniac]

I can live with the reality as long as it appears to be just that.

I was concerned that I really should be getting better than .35 mpg.

I still think I should be able to get at least .5 mpg.

That said, I am cancelling my planned Abaco trip. I think 350 miles round trip at .35 mpg and gas near $6.50 equates to almots $7k in fuel costs.

I had planned on it being somewhere closer to $4k.

I'm going to look into some of these ideas (trim tab upgrade, etc) and see what I can do to make it work better.

If my wife were a big girl, I'd put her up on the bow. But she isn't, so I'll have to find other solutions.

Wanna buy an F32 ? 1.1 mpg total at 18 knot cruise. Would save you GOBS of money!!

Just joking (about selling).

[BobCT]

What did you use to machine out the diverters? I would like to do that, seems like an easy upgrade.

Flame arrestors - do you have a pic of the old and new one by any chance? There's a lot of clearance on the mid cabins, I was going to try a higher carb plate (1") which a guy on my slip swears made a difference.

I looked at my flame arrestor and I'm guessing it's 3", definately not an 1". Maybe Crusader changed that?

I just ordered new props yesterday and will install next week. Based on what Sherman did, I went with 17x14's with a light cup (4 blade). Sherman, the guy from getaprop never called me back so I ordered Michigan Wheel props from another place. They don't do 1/2 pitch sizes so I'll compare notes with you on what the light cupping does.

Bob

[tsawyer]

My tabs look like they are 30 x 9.

Do you think 30x 12 drop fins would make much difference?

[RWS]

What did you use to machine out the diverters? I would like to do that, seems like an easy upgrade.

Flame arrestors - do you have a pic of the old and new one by any chance? There's a lot of clearance on the mid cabins, I was going to try a higher carb plate (1") which a guy on my slip swears made a difference.

I looked at my flame arrestor and I'm guessing it's 3", definately not an 1". Maybe Crusader changed that?

I just ordered new props yesterday and will install next week. Based on what Sherman did, I went with 17x14's with a light cup (4 blade). Sherman, the guy from getaprop never called me back so I ordered Michigan Wheel props from another place. They don't do 1/2 pitch sizes so I'll compare notes with you on what the light cupping does.

Bob

Bob,

I took the diverters (is that the right word?) to a machine shop and had them do it. As I recall they are cast iron?

On the flame arrestor mine were amazingly too small and it was an obvious problem. To change to the taller (3 or 4") I had to do a modification to the engine room deck lids.

John Leed at MarineTech gets the credit for those 2 modifications.

I don't think any one of the mods I did made the difference in improvement, I think it was the combination that did it. Props, tabs and the port side carb with the wrong metering rods were the most significant issues.

I sold these engines in 2005 and have no pictures that would be helpful.

Sorry.

RWS

[RWS]

My tabs look like they are 30 x 9.

Do you think 30x 12 drop fins would make much difference?

All I can tell youis that my running angle and fuel usage improved when I changed out the tabs.

For me it was a simple bolt on installation, using the same actuatators. The tabs share the same geometry. I did however have to get the right number directly from Bennett and then ordered them via my local chandelry.

Get your measurements and take a few photos. I'm sure Bennett can make this happen for you.

One las thing. With the diesels bigger props and increased torque, usage of the tabs changes nothing othert than the running angle, whereas with the gas engines you could watch the GPS speed imporove at any steady RPM by simply dialing in the tabs for the current boat load, wind and sea conditions.

My guess is that he drop fin tabs were not available when these boats were in production. Additionally if my engines were a tad on the weak side with a bnit less torque than factory fresh, that difference in torque combined with the load really made a difference in her "lift"

The original owner of my boat used to run from N. Miami to Bimini several times a year. He would load her up with lots of extra water, a big TV on the wetbar, lots of gear and a FREEZER strapped to the deck for his ballyhoo as he trolled for Marlin on the way over to the Bimini Big Game Club (the sticker is still on the side windshield)

My own impetus to adding these tabs was being similarly loaded in the local harbor when a storm came up creating some waves with a short fetch. With the load on board and full tanks, she just could not get her a$$ out oif the water and it was an umcomfortable ride back in the rain.

The tabs most certainly changed that.

RWS

[RWS]

I can live with the reality as long as it appears to be just that.

I was concerned that I really should be getting better than .35 mpg.

I still think I should be able to get at least .5 mpg.

That said, I am cancelling my planned Abaco trip. I think 350 miles round trip at .35 mpg and gas near $6.50 equates to almots $7k in fuel costs.

I had planned on it being somewhere closer to $4k.

I'm going to look into some of these ideas (trim tab upgrade, etc) and see what I can do to make it work better.

If my wife were a big girl, I'd put her up on the bow. But she isn't, so I'll have to find other solutions.

You should be able to get some very cost effective improvements here, without question.

First place to start is with a basic floscan unit. This will help you dial in your most efficient cruise RPM/speed.

It will also help identify problems like I had with one engine consuming 6 more gallons per hour due to the port quadrajet carburetor having the wrong meterting rods in the carb.

Identifying issues like that will easily pay for the floscan.

Once you get that data established, adding the modifications will take you a step ahead.

I would most definately do it !

RWS

[tsawyer]

RWS-

I had Roger install a set of Twinscans (replaced the original Tacs) a few months ago.

According to them, I burned 166 gallons on my way over. I actually put in 150, so I need to adjust callibration.

They were also showing the port engine burning more than the starboad engine.

As mentioned before, I am due for a bottom job. I'm thinking of having the props checks when the boat is on the hard.

I'm fairly close to where they drain fresh water into the brackish water. We also have a good 6-8 drop in tide. The growth in my area is fairly light.

What paint are you using?

[RWS]

I am on an electric boat lift behind the house, therefore I am required to use an ablative bottom paint for the in and out of the water issue.

Micron Extra. I have good results with this product.

Growth here is very quick and serious.

I had a similar problem with one engine using more fuel than the other. This is most likely a prop issue, however in my case I found that the port carb had the wrong metering rods in it.

A company in Miami-Ft. Lauderdale found the problem for me and I highly reccomend them "JUST CARBURETORS" is the name, the owner's name is Omar.

Are you getting a WOT of 4400?

My cruiser came with 4 blade bronze props and had a pair of spare 3 blade Nibrals still in the box. When I had the gas engines I ran her with both sets and (if I recall correctly) we got better speed with the 3 blades and better efficiency with the 4's. The mid cabin could have different results due to your different geometry.

All that said, I would not be satisfied with your current results. Something is simply not right.

Bottom

props

distributor spark advance

tabs

Let us know what you find.

I would post my 3 & 4 blade gas data for your benefit, however it really means little with the cruiser vs. the mid cabin.

Say hello to Roger for me.

RWS

[mhandley]

I am a new owner of a 1985 10 meter flybridge.

Ran her about 32 miles, used about 60 gallons, I think.

the fuel gage is erratic except when I have engines off. Need a new sender.

Some of the particulars:
twin 454's
velvet drives - 1.92:1
trim tabs, fully bow down (is that my problem?)
smooth waters
89 octane E10

Gonna put flowmeters on, but I am just moving in, and there are lots of things like that which I need.

[prowlersfish]

Unless your taps are way to small tabs full down will cause the bow to plow

[RWS]

I am a new owner of a 1985 10 meter flybridge.

Ran her about 32 miles, used about 60 gallons, I think.

the fuel gage is erratic except when I have engines off. Need a new sender.

Some of the particulars:
twin 454's
velvet drives - 1.92:1
trim tabs, fully bow down (is that my problem?)
smooth waters
89 octane E10

Gonna put flowmeters on, but I am just moving in, and there are lots of things like that which I need.

Couple of comments:

1. can't go by the fuel guage. Either measure the miles traveled between fillups or get the floscans.

2. E-10 is less efficient than real gasoline, and more obvious with an engine under load, like a boat on plane as compared to an automobile application.

3. There are two places to be for efficiency, the first is displacement or hull speed, the second is your most efficient planing speed which will differ SLIGHTLY from boat to boat. In your case with the flybridge you are carrying more weight and windage. BAsed on your trannys, can I assume this is the express cruiser version, not the mid-cabin?

RWS

[tsawyer]

Took her out today to do some testing.

Topped off with 144 gallons at $4.49. I figure the run back from Bimini was 112 gallons or .47 mpg

Well...I started with tabs up and in that state wot is 3300 rpm moving very slow and nose high.

Could not get tabs to go down. Resivoir was dry. I filled it up to find the stbd side line it leaking just below where it connects to the ram. I tried to play with it while in the ocean, but couldn't due to waves from other boats ( I was gonna get smacked in the head by the swim platform).
It was a flat calm day. Even with tabs up, shouldn't I be getting better than 3300@wot?

I'm 100% sure they were down when I got to Bimini and they were working on my ride back. I guess I'm glad they didn't break while in route.