PDA

View Full Version : LT-1 Power Upgrade Question


phil_edgecumbe
09-06-2013, 09:46 PM
I have a 1997 PS205 with LT-1 EFI engine. Current top speed at WOT is 45mph at 4600rpm. The engine (650 hrs) and propeller are standard.

I'd like to get a little more top end power/speed for barefooting. I was thinking of adding a Holley throttle body (52 or 58mm, up from the standard 48mm) to help the engine get more air however I'm not sure if the ECM would increase the fuel delivery to take advantage of the increased flow.

Or should I just change the prop...

1redTA
09-07-2013, 06:34 AM
Most here will tell you to change the prop :-). I though, would change the TB and look at a tune from Arizona Speed and Marine after I figured why it stops at 4600. The intake manifold is already bored for the 52 mm

bturner2
09-07-2013, 07:26 AM
For most boaters performance/reliability are going to be the most important aspects of a good boat. MC and Indmar have worked together to produce a power package that will deliver just that. Once you start modifying the power package without proper testing and equipment to monitor the effects of the modifications all bets are off. Speed shops are able to offer quality tunes for mustangs, Camaros and such because they can get test vehicles to test with. I seriously doubt many tuners will be able to say that about the engine/boat combination you have. Most likely any engine change you make will result in mixed results with any gains on one end being given up on the other.

If it were me I'd be calling Eric at OJ and getting a recommendation on a new prop. Based on the age of your boat you're probably running older technology and chances are it's not in like new condition either. This would be the safe bet, will cost you far less in the long run and will get you the best bang for you buck. Besides the worst you'll do going this direction will be to end up with a spare prop.

mikeg205
09-07-2013, 12:29 PM
Good I am not the only one who's max RPM tops out low.. :) - less wear and tear...

You could always do something like this... now I have lost count on how many times I have posted this link... ;)

http://www.youtube.com/watch?v=h7O9a9KBKfk

tommcat
09-07-2013, 12:33 PM
I have a 1997 PS205 with LT-1 EFI engine. Current top speed at WOT is 45mph at 4600rpm. The engine (650 hrs) and propeller are standard.

I'd like to get a little more top end power/speed for barefooting. I was thinking of adding a Holley throttle body (52 or 58mm, up from the standard 48mm) to help the engine get more air however I'm not sure if the ECM would increase the fuel delivery to take advantage of the increased flow.

Or should I just change the prop...what trans do you have? i have the exact same boat with a powerslot and with the stock prop my boat ran at 5100 rpms and topped out at about 52 mph(gps)
i propped down this year for the added ballast and still top out at 45 mph.

phil_edgecumbe
09-08-2013, 06:09 AM
I have a 1:1 transmission and the standard 4 blade prop. I can't get the prop nut off to check it's dimensions.

bturner2
09-08-2013, 09:48 AM
Looks like you found your starting point. No sense going any further until you know what you have. Remove the pin, get a block of wood and a wrench and get the prop off. You will also need a puller to take the prop off.

JimN
09-08-2013, 10:02 AM
I have a 1:1 transmission and the standard 4 blade prop. I can't get the prop nut off to check it's dimensions.

You need to remove the prop to find out what you have before anything else happens. 4600 is definitely low and you should have no problem getting more than 5000 RPM from this but you'll need to run some tests, preferably real-time data collection.

FYI- they didn't just slap an engine in the boats and call it "Done". They did a lot of testing before the boats were released for sale, bot on-water and on dynamometer. While it was being tested, one of the measurements was in-cylinder temperatures and unless you have the ability to ensure that the changes you make will work without damaging the engine, work on getting it to run the way it did when it was new, first.

Cloaked
09-08-2013, 10:08 AM
........Current top speed at WOT is 45mph at 4600rpm......I'd like to get a little more top end power/speed for barefooting.damn...

As Roy D. Mercer would ask, "How big a' boy are you?"

.

blackcreek
09-08-2013, 10:00 PM
I have a 1:1 transmission and the standard 4 blade prop. I can't get the prop nut off to check it's dimensions.
My 97 205 with the LT-1 and 1:1 transmission has a standard 3 blade prop. Recommended LT-1 WOT rpm according to my manual is 4200-5000.

blackcreek
09-08-2013, 10:21 PM
damn...

As Roy D. Mercer would ask, "How big a' boy are you?"

.

Maybe he has unusually small feet?

phil_edgecumbe
09-09-2013, 12:01 AM
Thanks for the responses guys. I've decided to "just go ski" rather than obsess about how to make the boat go faster.

Winter lay-up causes us boat owners to ponder these sorts of things.

In summer we just go skiing and don't worry about it...

tommcat
09-09-2013, 08:51 AM
Thanks for the responses guys. I've decided to "just go ski" rather than obsess about how to make the boat go faster.

Winter lay-up causes us boat owners to ponder these sorts of things.

In summer we just go skiing and don't worry about it...Even if you decide to not "go faster", i'd still look into why you are turning such low rpms. you may have an actual problem that needs addressing.

phil_edgecumbe
10-12-2013, 05:54 AM
Update:

Took the boat out for it's first run for the season.
I had the strut bushes replaced as they were a bit sloppy, prop checked/balanced and drive shaft alignment checked. The prop is the standard 13x13 4 blade version.
Filled the fuel tank with fresh petrol and added a bottle of Injector Cleaner.

It now does 48mph at 4800rpm with WOT. 3mph faster and no doubt running more efficiently.

Ben
10-12-2013, 08:22 AM
Good update. Depending on your situation, old also recommend not filling he fuel tank full. Less weight.

Mark rsa2au
10-12-2013, 08:46 AM
Good update. Depending on your situation, old also recommend not filling he fuel tank full. Less weight.
What??
My tank is not big enough for a full days sking anyway....

blackcreek
10-12-2013, 09:56 AM
Update:

Took the boat out for it's first run for the season.
I had the strut bushes replaced as they were a bit sloppy, prop checked/balanced and drive shaft alignment checked. The prop is the standard 13x13 4 blade version.
Filled the fuel tank with fresh petrol and added a bottle of Injector Cleaner.

It now does 48mph at 4800rpm with WOT. 3mph faster and no doubt running more efficiently.
Sweet! The LT-1 pulls timing if there is any knock due to using sub standard fuel. If you are going to be running wide open all the time I would recommend only high test fuel as a buffer against knock. From personal experience if you are running the original plug wires I would ohm out each wire for proper resistance. I had two wires that would not read any resistance meaning there was an internal break in the core. A spark will still jump if the internal break is small enough but it does lower the spark energy enough to lower performance. If you are still in search of more MPH I would talk to eric at OJ for proper sizing and type of prop. I was not aware that the LT-1 with the 1:1 transmission came with a 4 blade prop as standard. A three blade CNC prop might get you another MPH or two, but there are always trade offs.

Ben
10-14-2013, 11:57 PM
What??
My tank is not big enough for a full days sking anyway....

Not sure of your question. I was trying to say to run with less than full tank for skiing if possible. This would improve wake a little and maybe top end too.

88 PS190
10-15-2013, 12:16 AM
What??
My tank is not big enough for a full days sking anyway....

Just depends how your lake access is.

For folks like me who usually stop by the dock after ever hour or two, I seldom add more than about 10 gallons total to the tank, and that is only if I know we have 3-4 skiers in the boat, and beautiful conditions with no one waiting at home.

Otherwise I usually have 5 or 6 in when we leave the dock, and about 2-3 when we get back. Then I add another 5'er and go out again.


Folks who trailer to a lake/river and then go out all day tend to fuel the boat at a pump, and top it up.

Since I'm going off cans, I will seldom put multiple cans in the tank at a time, as mentioned, adds weight to the back, isn't great for the wakes.

mikeg205
10-15-2013, 12:24 AM
I run 41mph with my 4 blade had 43 with my 3 blade- have never seen tach go past 4500 RPM - less now with 4 blade but I expected that.