bertram31.com

The 454's are well known gas hogs but is there a difference in fuel consumption between the older carbureted engines and the newer multiport fuel injection models
Thanks
John

Yes,
Buddy was looking at 32 Luhrs and found the carbed boats used an additional 2-3gph at cruise. Not really worth converting over savings, but when looking for new power I would look into it.

I agree with Sim. There is a difference, but from what I've seen its fairly slight. When I had gas, I had floscans so I knew exactly what my 454's burned. At 3150-3200rpms I'd burn 30-32gph (18-19 knots). When I look at the tests in the boating mags, the fuel burn numbers they show are less, but not significantly so.

Also, a friend of mine installed Crusader 8.1's in his 33. He also has floscans. At the same 3150-3200rpms he is burning around 27-29gph and getting similar speeds. Not a lot of savings, but he can cruise those motors around 3500+rpms if he'd like with out destroying them.

General published industry data says up to 15% savings with throttle body and up to 30% with multi port.

Don't believe anything published by manufacturers. They all lie, by accident.

Last gas repower I did was few years back and it was a 28 Bert. Owner kept pretty detailed gas usage records on the fuel consumption on the carb'd engines.

After the MPI went in and even with a jump of 50hp a side he reported back after a year that the savings was about 21%.

His biggest problem was the increased torque and hp had him running his boat at a faster rpm and speed as the secondary noise was no longer.
Hard to keep his hands off the throttles.

Thanks for the replys.
Bruce...those secondaries do sound sweet when they open up...not worth 20% in fuel economy though. Happy my prospective purchase has the MPI engines.
John

I haven't got all the numbers in yet, but I just repowered from carb 454 330 Hp 1.5:1 BW to 496 Mag HO @ 425 HP with 2:1 ZF.

I haven't got big enough wheels yet, I moved from 18 x 19 to 20 x 20 with slight cup and can only run up to 70% throttle before hitting 5000 RPM. So I am sure I can squeeze some more efficiency out of them.

Basically the old 454's were a 3000 RPM cruise at 22 knots and 25 gal/hr or 1 MPG. These numbers are based on years of cruising at 22 knots. No flow scans, but I could tell you the exact amount of fuel it would take to fill just by looking at the trip odometer on the GPS.

Now with the computer data and GPS on the 496's is 3500 RPM @ 25 knots and 23 Gal/hr or 1.2 MPG. That's a 20% increase or 20% greater range and 20 % less cost. I also like the easy starting and the computer to monitor everything that is going on with the engines.

Next year I will spin the props higher, but at 70% of throttle and 5000 RPM is over 35 Knots. I wasn't paying attention pulling out of the harbor and pushed the throttles a little too far and hit the rev limiter and backed off, but I looked over and the max speed on the GPS now reads 42.4 knots. I don't think it will run that fast even with reproping, there was some current and wind etc, but damn that's fast in a 31.

Scott,

You have to be happy, for sure!!!!

Congrats!!!

Dug

Scott-

Sounds great. Getting the cruise up a few knots would be great. What speed you can get down to on one motor at idle for slow-trolling?

John

Woo Hoooooooooo

Thanks guys, yes I am happy with the engines. A very tight fit though. I don't think I will that 42.4 knots very often, even when propped correctly. I just sort of like seeing that on the max speed. However I am pretty sure I will be around 40 in the end.

As I said I am way under propped, I can't even come close to full throttle. It feels like a totally different boat. Sort of reminds me of my Ski Nautique, the way it jumps out of the water. I am going to go to 1 1/2 shafts this winter and more pitch on the props, but I wanted to be under propped instead of over propped this first season. However I must say I like the really slow speed at idle. It is around 3.5 knots on 2 engines. I can't tell on only 1 because I am just going in circles at that point.

The only thing that has plagued me this year is the starboard engine. I took the boat to Burr Brothers boats to certify the install and they went over and said it looked good. I pulled away from the dock at idle only and went about 100 yards and the alarm went off,. the starboard engine was badly overheating. The heat gun said the exhaust manifold was close 500 degrees and the paint was burning off. Turns out the "mechanic" used the air pump that these engines have to winterize the engines and pumped all the raw water out, leaving it with 15 PSI of air. They replaced the impellor and charged me $400 bucks. Next day I go out and the engine drops into Guardian mode (idle only) I bring it back to have them read the codes. I guess I was a little pissed at the damage they had done and the kicked me off the dock. I took it to another marine instead of looking at it myself because I smell a law suit coming and it turns out they forgot to connect the pressure sensor on the raw water pump. Since then I have replaced the knock sensors and found a melted wire to the oil pressure sensor. A bit of a nightmare, but she is run fine now. I just have to wonder how many hours that engine has lost due to there stupidity. The law suit will be filed soon and I know I am not paying the $400 bucks for the impeller they melted. The worst part is they wont even admit the F^&*ed up.

I feel Bob Lico Twitching to say something here about the 42.4 knots and got more to go...

Scot and others,

Everyone knows to get a decent marine repair tech is tough as it is.
To get one that is experienced is even harder.

To get one that has the ability to understand and perform tasks on new modern computerized engines is down right near impossible.

Add to that many of us who are good at what they do and failure of factories to properly train us. Add to that problems that are discovered by manufacturers and the failure to notify and update its dealer network on said issues and repairs.

Throughout this computerized engine repairs from the lightning strike I was continualy asked if I had a laptop and interface box to diagnose.

My answer was of course how the hell am I supposed to repair the engines without one?

Well the answer back was due to the cost of said diagnostic aids many dealers do not have them and try repairs using the helm displays which will work to a point.

The bottom line the owner gets screwed.

Just to head off Bob, I said it was in a current and I don't think thats how fast the boat was going, just a cool number to see on the screen.

scott,

what rpm does rev limiter kick in?

how do you determine the % of throttle that is applied?

thanks,

craig

The % throttle came from the Code reader. I had the guys at the marina, before they melted the engine, check the full throttle percentage so I would have an idea how much bigger props I would need. As far as the rev limiter, I don't really know. The max RPM is suppose to 4400 to 4800, I stopped pushing it to find the percent throttle at close to 5000.

However that one time when the alarm went off and the limiter kicked in, I still hand my hands on the throttle and just immediatly pulled back, but my guess and Bruce might know better, would be around 5500.

STraenkle wrote:Just to head off Bob, I said it was in a current and I don't think thats how fast the boat was going, just a cool number to see on the screen.

Scott, in a current, with the wind, sliding down the back of a wave...it's all cooool.

Most all the engines have what they call a reduced power mode when certain codes are detected.

This could be RPM, Oil press, water temp, knock sensor, etc.

BTW the computer also stores these codes to be read later. What many owners don't realize in the fine print of some warrantees is that if certain parameters are exceeded, the warrantee is void.

This prevents manufacturers from having to replace engines due to the carelessness of the operator.

It is very important to read and understand your warrantee and its limits these days. Don't depend on a dealer to tell you as most of the dealers are idiots.

BTW


We all know the 31 is capable of speeds approaching 50 mph.

Lets NOT get into a pissing contest over it.

Understand-Computerized engines are good for the manufacturers...you're made to think they're good for you. Like Easy-Pass, you feel good missing the long "cash" lines, but you forget the fact that your insurance company now knows that you speed a lot. Walter