Mileage varies greatly for F-Series

JuiceClark · Post by **JuiceClark** » Tue Jul 31, 2007 3:58 pm

You know how a boat with a flatter, wider hull at the transom gets better mileage? Well, on the other hand if your draggin' ass it can work the other way. So, you gotta get that baby trimmed just right.

The seas were absolutely glass flat on Sunday as my wife and I made the 50 mile trip from Boca Grande home. This gave me a chance to mess around with the trim tabs and rpm and their effect on the Floscan and mph.

I couldn't believe how the slightest change in the tabs affected the speed. I've been running with the bow too high. At a slow cruise (about 2950rpm) the speed increased from 17.2 to 18.4 with the bow pulled down a barely noticable amount. Then, realizing the port side was just barely lower, increased to 18.7 mph when running perfectly level.

When I backed the throttle to where I was moving 17.2 mph again, it was a full 2 gallons per hour less than when I started. So, by fixing the tabs I decreased fuel consumption a full 10% to go the same speed.

Stripermann2 · Post by **Stripermann2** » Tue Jul 31, 2007 7:13 pm

Absolutley...

Another thing, when I'm cruising and need to slow the boat, I simply bow up, then will resume adjustment for my optimum efficiency with a little bow down. This way, I never have to re-sync engines and bring them back up.

Jamie

chumwithabottleofrum · Tue Jul 31, 2007 7:48 pm

Juice-is Boca Grande anywhere near Del Boca Vista?

briansselectautos · Post by **briansselectautos** » Tue Jul 31, 2007 8:07 pm

I haven't put much thought into my tabs yet, I am restoring my f-24. It had bennett tabs that are inop. I have been looking and bennett systems are real pricey and it sounds like they are troublesome, I was wondering about the lenco electric replacements? any input? also it has 9x18 tabs is that to big for a 24'?

chumwithabottleofrum · Tue Jul 31, 2007 8:38 pm

brian-have you tried trouble shooting your existing tabs?-fluid, power to the hydraulics, fuse(?), bad switch, etc. Bennets tabs are pretty durable you maybe able to save some $$$

RWS · Post by **RWS** » Wed Aug 01, 2007 6:16 am

Juice,

When I was running the gas engines on my 10 Meter, I put an inclinanometer at the helm. I took my performance numbers to the Bennet booth at the boat show and determined that increasing the trim tab size and adding drop fins would provide the additional lift necessary.

I increased length from a 9" to 12" and addded the drop fins which effectively doubled the effective lift area. Effeciency increased significantly, especially at speeds between 14 - 17 kts. (Confirmed with Flowscans, GPS and digital tach/synchronizer)

Perhaps the factory spec'd the 9" units assuming all buyers wiould run at higher speeds. I didn't because I feared for the life of my worn 454's and rarely ventured above 2900 unless I was testing an improvement.

Interestingly, with the Yanmars, applying any tab whatsoever lowers my speed. It seems that the new props and associated torque are getting the ass end of my wide beamed hull out of the water like never before. Now we only use the tabs rarely, when the sea conditions require a sharper entry.

We were at Cayo Costa (Pelican Bay) on Saturday. Perhaps sometime our paths will cross a bit closer sometime.

RWS

briansselectautos · Post by **briansselectautos** » Wed Aug 01, 2007 7:18 am

I would have happily saved anything that I could however the previous owner pretty well gutted the boat for anything valuable, including the trim pump and left the broken switch, cylinders and tabs that are in poor shape so this is why i am considering other options....

willietrojan · Post by **willietrojan** » Wed Aug 01, 2007 9:13 am

JuiceClark,

What model boat do you have, and what engines?

JuiceClark · Post by **JuiceClark** » Wed Aug 01, 2007 9:48 am

Hey Chum,
No...Boca Del Vista, with all the NYC retired Jews from Seinfeld is in North Miami. We're on the Southwest Gulf Coast...thank God!

Brian,
My boat came with the el cheapo trim tab pump and it didn't work. But I took it apart, cleaned all the contacts around the pump and it has worked well ever since. I hope it holds up for a while because I hate to buy new crap. When a hose broke near the pump unit, I put one of those heat shrink things for wires over it, a glob of 5200 and a hose clamp...hasn't leaked again yet. I would have wrapped duct tape around it too but that stuff is like 10 bucks a roll!

Willie,
It a 1981 F-36. Here it is:
http://www.yachtworld.com/core/listing/ ... 59430&url=

rossjo · Post by **rossjo** » Wed Aug 01, 2007 9:51 am

Medium Tab Position works best on my F32 with twin Cummins 6BTAs. Too much tab "plows" , while no tabs rides high ... precise tab setting is critical to good fuel economy and speed!

I have the factory 9" Tabs, but have a set of 18" Kiekhaefer racing tabs I am thinking about adding, but hate to "waste" these jewels on a slow boat. I do think the added 9" of length would provide a better riide ... (another project!).

Interesting artcile (by Bennet) on Electric vs. Hydraulic ...
http://www.bennetttrimtabs.com/trim_tab_comparison.htm

I would be a little concerned about electric tabs on a boat that stays int he water,. I have seen Lencos go bad adnd have to be sent back ...

RWS · Post by **RWS** » Wed Aug 01, 2007 10:41 pm

[quote="JuiceClark"]Hey Chum,
No...Boca Del Vista, with all the NYC retired Jews from Seinfeld is in North Miami. We're on the Southwest Gulf Coast...thank God!

Juice, it's interesting that you "thank God"

If you're a Christian, then you would be thanking a Jewish God.

I wonder how he would feel about your post ?

And I thought this was a Trojan Boat forum.

No one did or said anything that would justify your ignorant comment, which really has no place here on the Trojan Boat Forum

RWS

prowlersfish · Post by **prowlersfish** » Wed Aug 01, 2007 11:02 pm

RWS I don't think Juice ment any harm or to offend anyone

JuiceClark · Post by **JuiceClark** » Thu Aug 02, 2007 11:39 am

I think I put the "retired Jewish guys from Seinfeld" and "thank God" I don't live over there comment too close together. Despite my tendency to believe people are too easily offended, I must insist those two comments were mutually exclusive. The busy stock market has me writing in sloppy fashion. It's all the concrete that bothers me, not all the Jews...including my in-laws in West Palm. (well, actually the in-laws bother me just a bit)

gopher · Post by **gopher** » Thu Aug 02, 2007 10:14 pm

Pity about the F24 being gutted like that..
You try Ebay for any used tabs or leads from marine supply places..

I always thought the 24 was a neat design when I saw it as a young teen.

Greg
26 Express

briansselectautos · Post by **briansselectautos** » Thu Aug 02, 2007 11:48 pm

If ebay were a place I would live there! 80% of the parts I've got have come from that site.
however, tab sets are in the $300 range for well used. Im too cheap so that will never do.
I was disgusted with how badly gutted the boat was. I bought it sight unseen... for the trailer mostly, which was easily worth what I paid.
I just fell in love with the boat, and decided to fix it. So far I have repaired the transom, stringers, deck rails, bulkheads, floors, and topside deck. and replaced the engine, outdrive and controls.
I know you're all thinking i'm crazy after that but the project is really moving along, I've had it for 6 months and its half-way done and it is underbudget thanks to Ebay!
I plan to see her maiden voyage this month, she won't be pretty yet, but operation is beauty in itself.

Trojan Boat Forum

Mileage varies greatly for F-Series

Mileage varies greatly for F-Series

trim tabs that important?

tabs

various BS

Medium Tab Position

Re: various BS

oops

ebay... worlds pawn shop