LT-1 Power Upgrade Question

[phil_edgecumbe]

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]

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]

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]

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]

Originally Posted by phil_edgecumbe

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]

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]

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]

Originally Posted by phil_edgecumbe

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]

Originally Posted by phil_edgecumbe

........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]

Originally Posted by phil_edgecumbe

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.