Trojan Boat Forum

Hi all. Boats an '81 F26 with a Merc 228, GM 305. Just installed a Floscan fuel flowmeter with a totalizer. Did a run today, and here's what I saw.

WOT- 4100 RPM, 18 GPH, 23 KTS
3500 RPM- 15 GPH, 19 KTS
3100 RPM- 10 GPH, 17 KTS
2800 RPM- 12 GPH, 13 KTS, starting to fall off plane
2000 RPM- 12 GPH, 10 KTS, not planing, just mushing through the water
1500 RPM- 8 GPH, 8-9 KTS
1000 RPM- 2-3 GPH, 6 KTS
650 RPM- 1-2 GPH, 3 KTS

Anyone with a fuel flowmeter, do these numbers look correct? I have always thought that the boat was "happiest" at 3100RPM.

Thanks.

My 1971 F26 seems to run best at 3000 rpm. At 3000 rpm I get 18 knots at 11 gph.

When I first bought my '78 F26HT, it had the same engine as yours with a 14 x 10 prop (1:1 Velvet Drive) and the RPMs and kts were pretty close to yours. No Floscan though so I cant help you out on the GPH.

Hope this helps

I am thinking of buying new Floscans for my F28 which has twin Chrysler 318's. Your data shows that cruising at the sweet spot can result in big fuel savings on the basis of miles/gallon. Given I average about 1mile/gallon I think the new Floscans could quickly pay for themselves! Thanks for posting the info.

Where did you tap into? Most ofy fuel lines are copper. I picked up a lowrance and it has 3/8 barb fittings on it for rubber gas line. Any suggestions? The only rubber hose I have looks much larger than 3/8s. Thanks.

The rubber hose going from the boats line to the fuel pump should 3/8 . It may look larger , because marine fuel hose is a Little thicker . Some of the older hoses are real thick walled.

This would be a good time to replace the hose as it only lasts so long and the newer hose is rated for todays fuels . Make sure its CG approved marine fuel hose for inboard use . The hose should have the rating on it A1-15 ( older rating A1 ) . Don't use the outboard hose (B1 or B1-15).

akwalker wrote:Hi all. Boats an '81 F26 with a Merc 228, GM 305. Just installed a Floscan fuel flowmeter with a totalizer. Did a run today, and here's what I saw.

WOT- 4100 RPM, 18 GPH, 23 KTS
3500 RPM- 15 GPH, 19 KTS
3100 RPM- 10 GPH, 17 KTS
2800 RPM- 12 GPH, 13 KTS, starting to fall off plane
2000 RPM- 12 GPH, 10 KTS, not planing, just mushing through the water
1500 RPM- 8 GPH, 8-9 KTS
1000 RPM- 2-3 GPH, 6 KTS
650 RPM- 1-2 GPH, 3 KTS

Anyone with a fuel flowmeter, do these numbers look correct? I have always thought that the boat was "happiest" at 3100RPM.

Thanks.

We have the same powerplant(s), and I think they are great.

What I find interesting is that at 2800 you are falling off and at 2800 I am in need of some trim up. I agree that 3100 seems to be a comfortable 'groove' for these engines, but at that point I am using some serious tab, and find a much more economical speed is around 27-2800; much less trim and still frimli ON the water.

I know that these boats aren't quite the same in displacement, beam, or profile; but I find it interesting that you need 2800 to hold plane. Is this typical of the single screw F series?

Also, at 3100 I am doing a bit more than 17 knots. Starting to crack 20 by 3100.

CP I find it strange you neeed more Tab at higher rpm / speed .

Commissionpoint wrote:

akwalker wrote:Hi all. Boats an '81 F26 with a Merc 228, GM 305. Just installed a Floscan fuel flowmeter with a totalizer. Did a run today, and here's what I saw.

WOT- 4100 RPM, 18 GPH, 23 KTS
3500 RPM- 15 GPH, 19 KTS
3100 RPM- 10 GPH, 17 KTS
2800 RPM- 12 GPH, 13 KTS, starting to fall off plane
2000 RPM- 12 GPH, 10 KTS, not planing, just mushing through the water
1500 RPM- 8 GPH, 8-9 KTS
1000 RPM- 2-3 GPH, 6 KTS
650 RPM- 1-2 GPH, 3 KTS

Anyone with a fuel flowmeter, do these numbers look correct? I have always thought that the boat was "happiest" at 3100RPM.

Thanks.

We have the same powerplant(s), and I think they are great.

What I find interesting is that at 2800 you are falling off and at 2800 I am in need of some trim up. I agree that 3100 seems to be a comfortable 'groove' for these engines, but at that point I am using some serious tab, and find a much more economical speed is around 27-2800; much less trim and still frimli ON the water.

I know that these boats aren't quite the same in displacement, beam, or profile; but I find it interesting that you need 2800 to hold plane. Is this typical of the single screw F series?

Also, at 3100 I am doing a bit more than 17 knots. Starting to crack 20 by 3100.

I think twins vs a single has alot to do with your being able to maintain plane at lower RPM. You have twice the torque working for you, in theory.

Maybe I miss spoke a bit. At 2800 I'm still planing and able to maintain 13-14 kts, but can tell I'm close to the break point. At 2500, I'm falling off.

prowlersfish wrote:CP I find it strange you neeed more Tab at higher rpm / speed .

I really meant to say I need more 'up' trim, as I begin to nose down above 3000.

akwalker wrote:I think twins vs a single has alot to do with your being able to maintain plane at lower RPM. You have twice the torque working for you, in theory.

Maybe I miss spoke a bit. At 2800 I'm still planing and able to maintain 13-14 kts, but can tell I'm close to the break point. At 2500, I'm falling off.

Yeh. Its really hard to compare the two I know. While I may have twice the torque, and probably a lot more thrust (15x16's and a 1.52 reduction) I also am about 5 feet wider, 3 1/2 feet taller, and have you outweighed by almost 3 times. So you can see maybe my logic in wondering how close they were insofar as performance numbers are concerned.

I have the only Merc powered Trojan here in my home waters that I know of, so I am always curious what some of you other Merc powered guys are getting for performance. Even if we don't have the same hull models. I see lots of Chrys/Crus, but Mercs are elusive, espescially in the bigger F boats.

Commissionpoint wrote: I also am about 5 feet wider, 3 1/2 feet taller, and have you outweighed by almost 3 times. So you can see maybe my logic in wondering how close they were insofar as performance numbers are concerned.

The F-32 has a 15 1/2 foot beam?

the 26 has a 10 1/2 beam?

Yup, she's fat. See's also fairly tall which is what makes the cabin so roomy in a 26' boat.

that is wide. the beam on the 32 is also what helps it so much in the interior.