28 Luhrs repower

[7228sedan]

I just purchased a 72 28 foot Luhrs Flybridge sedan with a Merc 454 & velvet drive 72 series V drive. The transmission is in need of a rebuild. I am looking to see if there is anyone out there with the same or a similar combo. The transmission is a 1.5:1. Based on my research, the boat weighs around 11,000 lbs. I am figuring that the boat should have a 2:1 ratio with a new prop to enable the motor to spin up to the correct wot rpms 4200-4400. I am not yet sure of the current prop's size. The previous owner only ran the boat once before the transmission went. He indicated tha tthe boat hit about 18 mph at wot. He did not remember the rpms though.

 

[mkast]

Re: 28 Luhrs repower

Without knowning what the engine is turning at wide open throttle, you are guessing. What if the engine just needs a tuneup to reach WOT?
You want to change gear ratio and propeller size without any real information.

 

[7228sedan]

Re: 28 Luhrs repower

The motor may indeed hit an appropriate wot rpm. As I need to rebuild the transmission now, and this is a repower; I do not want to assume that the ratio is correct. I was hoping that someone had a similar set up and could advise me on what their ratio & performance is. I don't want to change anything if I don't have to. But now would be the time to change if it requires it.

 

[mkast]

Re: 28 Luhrs repower

this is a repower

Then the question is, what engine are you using for the repower?

 

[7228sedan]

Re: 28 Luhrs repower

The boat was repowered with the current 454 not too long ago. The boat most likely had a Chrysler 360 with a paragon V drive from the factory. Now it has the 454 with velvet drive V drive. My experience tells me that this hull should have a higher ratio due to the weight. I had a 26 ft express cruiser with a 7.4MPI 2:1 Bravo 2 and it ran like a champ. That boat originally had a 1.5:1 Bravo1 and a higher pitch prop. With that set up it wouldn't plane with a full tank of fuel & toppeed out at 3500 RPM's. That boat was only 6500 lbs dry weight. Granted apples & oranges from a Deep V plainig hull with a stern drive vs a semi displacement inboard boat. But I do not have confidence in the repower that was done.

 

[Bondo]

Re: 28 Luhrs repower

But I do not have confidence in the repower that was done.

Ayuh,... Welcome Aboard,...
To be honest, there's not alota Big boaters here at iboats,... We see very few V-drives..
Mostly 17'/ 25' I/O stuff...
I'll bump this to the top again,+ Maybe it'll get a hit from somebodyelse...

Good Luck...

 

[captk]

Re: 28 Luhrs repower

Luhrs were always considered a "lead sled" semi displacement and slow but comfortable. You can spend alot of money trying to improve your speed but it aint gonna happen. enjoy your smooth if slow ride.

 

[7228sedan]

Re: 28 Luhrs repower

I'm not looking for speed. I want to gear & prop the motor so it's not overloaded. I'm looking for efficiency more than anything. If I can hold the boat on plane at 10-12 knots around 2500-2800 RPMs I could keep the fuel consumption down significantly. Thanks