FireFish Convict 17 foot 6.2 212 fuel burn.

ABMax24 · Oct 9, 2020

Chrisco said:
If I was a betting man I would say that a 6.5 Piranha hull weighs more than a 17 foot Convict hull. In my experience once you own a 212 you will never have to buy another impeller again, 400.00 bucks exchange program to rebuild. I honestly don't think the performance would be the same as a Convict with a Eco 212.

You're probably right that the piranha hull is heavier than a Convict, but the weight difference is really in the powertrain. IIRC the Eco motor is right at 500lbs, plus 160 for a 212 pump. So by time you add the driveshaft you're knocking on the door of 700lbs.

The rotax engines are right at 220lbs, adding another 80 lbs for the driveshaft and pump (which is generous), and another 50 for muffler and heat exchanger brings us to give or take 350lbs. Which would be just a bit heavier than the old 175 sport jets at 305lbs.

The 16' piranhas with a 175 sportjet used to be right at or just shy of 40mph. I think 250hp in the same hull would get close enough to 50mph for me. I think they'd both run equally shallow, the convict would be heavier but is also got more wetted area to pack that weight.

Don't get me wrong, the Convict is a beautiful boat, and work very well, and if I come across a deal on one that's what I'll have. But for the boating I want to do a rotax will be fine, and the price point is there too.

iceman5689 · Oct 9, 2020

ABMax24 said:
13' Brattjet with a 215, I guess it would be the Menace but I bought mine before they called them anything.

They definitely are, particularly now that they can be bought by builders as a complete package without having to buy a seadoo.

I think the next boat I want is a 16' Firefish Piranha with a 250 or 300 Rotax in it. But I need to try and find some fuel burn numbers, I'm scared that when these new 1603 rotax motors start working they get thirsty like my 215 does. For example my 215 burns about 20 gph at WOT to make 215 hp. The 6.2 L86 is supposed to burn 30gph at WOT but making about 375hp by comparison.

Hate to tell ya but you ain’t getting 215 at the pump, more like 114hp with the pump curve. Just like any boat run it at 7800rpm it drinks the fuel back. My rotax seems to be most efficient at 4800rpm on step. But let’s face it who want to Cruze at that.

ABMax24 · Oct 9, 2020

iceman5689 said:
Hate to tell ya but you ain’t getting 215 at the pump, more like 114hp with the pump curve. Just like any boat run it at 7800rpm it drinks the fuel back. My rotax seems to be most efficient at 4800rpm on step. But let’s face it who want to Cruze at that.

Yeah that's how jets work, lots of losses in them. But the motor under ideal conditions would make 215hp at the crank.

iceman5689 · Oct 9, 2020

Just like the Hp talk that’s it. Depends if your the rear wheel or pump Hp guy or the crank guy.

Chrisco · Oct 9, 2020

ABMax24 said:
You're probably right that the piranha hull is heavier than a Convict, but the weight difference is really in the powertrain. IIRC the Eco motor is right at 500lbs, plus 160 for a 212 pump. So by time you add the driveshaft you're knocking on the door of 700lbs.

The rotax engines are right at 220lbs, adding another 80 lbs for the driveshaft and pump (which is generous), and another 50 for muffler and heat exchanger brings us to give or take 350lbs. Which would be just a bit heavier than the old 175 sport jets at 305lbs.

The 16' piranhas with a 175 sportjet used to be right at or just shy of 40mph. I think 250hp in the same hull would get close enough to 50mph for me. I think they'd both run equally shallow, the convict would be heavier but is also got more wetted area to pack that weight.

Don't get me wrong, the Convict is a beautiful boat, and work very well, and if I come across a deal on one that's what I'll have. But for the boating I want to do a rotax will be fine, and the price point is there too.

Just make sure you can put a sand trap on that Rotax I have a buddy with a new 16 foot center console and he has had a lot of issues with plugging the motor up and overheating. He has been trying to build a sand trap system for it working with Steve.

gunner3006 · Oct 9, 2020

Hey Chris. What does that boat hold for fuel?

There’s no replacement for displacement. Impressive how low you can run your rpm’s and still stay on step. Lots of torque with the 6.2. No one cares about hp in the jet boat world. Torque torque torque.

Cheers
Chadd

NoBrakes! · Oct 9, 2020

aluminum DI 5.3 or 6.2 and 212 is the go to for a reason. The cheap man pays twice.

neilsleder · Oct 9, 2020

I don’t think that kotax motor and pump is the answer. Between sand issues, pump seal issues and weak impellers I would spend more and get a v8 and pump.

catalac · Oct 9, 2020

Have heard A few owners talking about the new ecotech 2.3 sounds like Indmar have few bugs to work out. From what I’m hearing I wouldn’t have one for a while yet, thinking the extra weight of an ls3 worth it.

iceman5689 · Oct 11, 2020

neilsleder said:
I don’t think that kotax motor and pump is the answer. Between sand issues, pump seal issues and weak impellers I would spend more and get a v8 and pump.

Proper sand filtration/ shell and tube heat exchanger. Stainless wear ring and impeller. Good to go. All parts relatively inexpensive comparable to a Hamilton or Scott pump on the a big/ small block

Chrisco · Oct 13, 2020

gunner3006 said:
Hey Chris. What does that boat hold for fuel?

There’s no replacement for displacement. Impressive how low you can run your rpm’s and still stay on step. Lots of torque with the 6.2. No one cares about hp in the jet boat world. Torque torque torque.

Cheers
Chadd

Holds about 220 liters gives me a range of 200miles safely.

dixopr · Oct 13, 2020

Back to the thread I'm really happy to see these numbers because after this year I know my numbers pretty good. I just got back from 72km up and down river (current speed is about 10km/h). I ran a constant 3200rpm on a 212 with a 3.4kw running 55km/hr down and 45/hr up plus or minus with 100 gallons of fuel, a bunch of crap, 5 adults 8 16 foot 2x6 and 6 sheets of plywood and tools down stream and some misc junk on the way back. I burned exactly 132L of fuel. carb 350 KEM. (22 foot 6.5 foot 10 degree)

I came back from 98km down stream with a moose and myself running around 3100rpm or a little less and filled up with 3 big jerry cans. I used 100 liters going up stream though.

Anyway. constant speed cruising is the best way to figure your fuel burns at least in my opinion.

neilsleder · Oct 13, 2020

dixopr said:
Back to the thread I'm really happy to see these numbers because after this year I know my numbers pretty good. I just got back from 72km up and down river (current speed is about 10km/h). I ran a constant 3200rpm on a 212 with a 3.4kw running 55km/hr down and 45/hr up plus or minus with 100 gallons of fuel, a bunch of crap, 5 adults 8 16 foot 2x6 and 6 sheets of plywood and tools down stream and some misc junk on the way back. I burned exactly 132L of fuel. carb 350 KEM. (22 foot 6.5 foot 10 degree)

I came back from 98km down stream with a moose and myself running around 3100rpm or a little less and filled up with 3 big jerry cans. I used 100 liters going up stream though.

Anyway. constant speed cruising is the best way to figure your fuel burns at least in my opinion.

You post this trip on Facebook? I think I seen the post

gunner3006 · Oct 13, 2020

dixopr said:
Back to the thread I'm really happy to see these numbers because after this year I know my numbers pretty good. I just got back from 72km up and down river (current speed is about 10km/h). I ran a constant 3200rpm on a 212 with a 3.4kw running 55km/hr down and 45/hr up plus or minus with 100 gallons of fuel, a bunch of crap, 5 adults 8 16 foot 2x6 and 6 sheets of plywood and tools down stream and some misc junk on the way back. I burned exactly 132L of fuel. carb 350 KEM. (22 foot 6.5 foot 10 degree)

I came back from 98km down stream with a moose and myself running around 3100rpm or a little less and filled up with 3 big jerry cans. I used 100 liters going up stream though.

Anyway. constant speed cruising is the best way to figure your fuel burns at least in my opinion.

You pitched a moose in your 17’ firefish convict. Sounds western. Let’s see the pics.

dixopr · Oct 13, 2020

No I didn't post to Facebook. Put the moose in a 22 footer. I'll see if I can post a photo tomorrow. I have some good photos of last year's moose. This year was not as spectacular.

For Western we put 2 moose in a 16 foot Lund with 3 guys.

dixopr · Oct 14, 2020

4 moose in the one photo and the big bull in my boat.

Chrisco · Oct 14, 2020

dixopr said:
4 moose in the one photo and the big bull in my boat.

derail....

dixopr · Oct 14, 2020

I know, sorry.

So funny because I tried to get it back on point with my fuel consumption story. So in that regard Chrisco, you have any info on your boat performance and fuel numbers other than a total km and litres used? What your minimum on step speed and rpm, what is your most efficient cruise speed? etc

I sorted my upstream down stream avg to about 4gpm which I think is pretty good for 22 foot boat with a carb 350

skegpro · Jul 3, 2021

ABMax24 said:
The trapper isn't quite what I want. I want a traditional window boat just on the smaller side. Nothing against Brattjet I love my mini, but the Piranha has been around for a while and is a tough proven design. I was actually talking about it with Steve today, if I decide to pull the trigger on a boat for spring it'll be a 16.5' Piranha with a 250 Rotax powerplant. I figure I'll get very similar performance to the Ecoboost powered Convict in a lighter more cost effective package. So far I've been impressed with the rotax powertrain I already have, and I like that I can pretty much replace the entire pump for the same cost as a new impeller and wear ring on the 212.

Did you ever pull the trigger on this? Wondering how you like it?

ABMax24 · Jul 3, 2021

skegpro said:
Did you ever pull the trigger on this? Wondering how you like it?

No I never did, work slowed down and I wasn't going to finance it to pay for it.

Here's a couple videos of them though, they can practically run on wet rocks. It's still the boat I want, except I'd get a window boat with a full engine cover and rear bench seat.

FireFish Convict 17 foot 6.2 212 fuel burn.

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