Trojan Boat Forum

This is what i got.

Pair of fresh Marine Power (320's) 454TBI's
BW 5000 7* down angle gears (2.04:1)
1-1/4" shafts
18 x 19 3 bladed no cup props
3/8 tank of fresh fuel
dirty bottom
tabs up/out of the water

RPM-KTS
1000-4.8
1500-6.8
2000-8.8
2500-11.9
3000-15.7
3500-19.0
4000-21.3
WOT 4400/4300 is 23.5

Does this sound right. I would like to get about 10 kts more out of it WOT and a 25 kt cruise. Am i dreaming?

Mike

You maybe dreaming ,But it will do a lot better with a clean bottom

Yep, a clean bottom and running gear is the difference between night and day. Why make your fresh motors work harder than they have too plus you'll be getting better fuel mileage.
You'l want to plane out with the tabs once you've figured a good target cruise speed.

You are running bow high not using your tabs. Run the 2500 and up with your tabs down, then adjust the tabs to find the best cruising speeds and angle.

Cupping your props will help. I just changed over to 4 blades in my midcabin and it is a whole new boat.

I think RWS 10M express was running 4 blades on his gas engines before he switch to diesel.

He should be able to give you the best advice. The stock 454s were 350hp, so your 60hp short may be the difference.

This boat won't plane off. By tabbing down it doesn't lift the stern and drop the bow like performance boats. It is like a small under powered inflatable boat.

These boats don't have lifting strakes. I have been on at least 5 of the same boats (10 meter express's) and they don't (plane off). Some do go faster than others.

Tabbing down will give me a better ride but it drastically adds more drag to the hull and slows it down. The stern does not have any lift. Thats why i am thinking of going to 4 bladed skewed props. I have been told that big old lugs like my boat jump out of the water with these.

This just got me thinking if my tabs are too small. They are only about 20" wide. They seem small for this boat. Can you guys tell me how wide your are? and how deep?

Am i wrong? probably been doing it wrong all these years.

Oh yeah, by wanting 10 more knots, I didn't mean with this setup. Im thinking of going to 496's.

You may or may not gain by going to 4 blades some boats do and some don't could slow you down , skewed props ? wrong boat

instead of spending 3 grand on props 20-30 grand on engines , why not spend a few hundred or less and clean the bottom , thats the only thing that will make it jump out of the water ,

tabs can help you cruising speed by make the hull run at a more efficient Angle , more the compensating for the tab drag .

If you worried about tab drag go with larger tabs ,they reduce drag because you use less angle for a given amount lift

Prowler, I am hauling the boat next week to put in a new transducer and going to give the bottom a good cleaning. Thank you for the advice. I will post a new set of performance specs.

Mike

You maybe in for a pleasent surprize

I agree - a clean bottom has more impact on performance than most people would actually believe. When you consider how many square feet of surface area contacts the water, having as clean a bottom as possible and getting rid of all of the parasitic drag that you can will really improve performance.

What are you you all using for fuel flow guages? I've used Floscan guages before, and they were dead on accurate.

The boat I'm looking at has no fuel flow guage.

Tom

I have the same engine/hull design as you do.

A brief WOT test in 2003 shows WOT rpm 4480 (digital tachometers/synchronizers) and a speed of 26.4 kts/ 30.4 mph

The graph below stops where I was uncomfortable with high engine RPMS on my tired engines.

RWS
==================================
1982 Trojan International Express Cruiser
10 meter (33') with a beam of 13'
Harry Schoel Delta-Conic Hull design
454 Crusader 3330/350 HP original carbureted engines
published weight 12,500 lbs dry - questionable weight for stripped down vessel, actual dry may be 14,000 +,-
test run 2/10/04
Tests done with digital tach/synchronizer, GPS and flowscan
After replacing the secondaries metering rod brackets to original
corrected carburetor metering rods
Props 4 blade 18 x 19
stock 9x24 trim tabs replaced with 12x24 tabs with 3" drop fins
2 Adults
sea conditions very smooth
carrying 40 gal water and 143 gal fuel

==================================

TThis boat has a Delta Conic hull that is made to plane and plane well at slower speeds. Trim tabs cause more drag than effeciency? why do you think they make them, and thus call them TRIM tabs, they trim the boat out for you. Use them and see a true difference. Once planed you can adust trim and speed. When you look behind you you are probably carrying a large swell wake if your not planing. This is due to drag, and is very inefficient for fuel burn and speed. Ditto on the clean bottom, amazing how a little crud slows you down. Clean and trim and watch the numbers change.

I don't have an International, but what I would have expected (since the Delta Conic hull was supposed to be such a technological improvement over previous designs and you have that much more power) is a cruise around 3000-3200 RPM to be about 18-20 knots (21-23 mph), and a WOT in the neighbourhood of 4000-4500RPM about 26+ knots (30+ mph). If my lowly 1979 F32 with almost 1700 hours on (original) twin Chrysler 360s can do these numbers, your configuration should be able to do it as well...

Problem resolved yet?

RWS

Proplem ? I don't think he had a proplem just a very large want