96 venom 200 lost SPEED

[muller2357]

hi all

had the boat about 8 months
20' 7" sprint bass boat would run 67-68mph on gps @5500 rpm
with a 13.5" X 25" renegade 4 blade ss prop
no jack plate

two months ago running about 55mph driveshaft snaps right at pinion bearing
replaced lower unit with a used unit from a marina in town
only reused my upper driveshaft and shift rod from old unit

now when i m running wot i am at a 6100 rpm and 54 mph (speed checked on two different gps units)

checked gear ratios of old and new lower units
both are 14:26 or 1.86 to 1

where did my speed go?

thanks for any ideas

 

[Faztbullet]

Re: 96 venom 200 lost SPEED

The prop calculator show that you have almost 30% slip!! if its a lighting case I would check prop as the early case would burn out prop hubs. Also the lighting case is for 70+ mph setups.

 

[muller2357]

Re: 96 venom 200 lost SPEED

yeah i did the calculation last night and thats what i got 30% is really high

that was what i was going to look at next was to see if the prop is slipping on the hub
two questions though

my hole shot isnt terrible....is the prop more likely to slip on the launch or trimmed out at higher speed?

and second how can i tell if I have a lightning gear case?

thanks

 

[Faztbullet]

Re: 96 venom 200 lost SPEED

The lighting has a factory nose cone and lower side pickups. A prop hub usually slips on hole shot. Did you transer the plastic blw out ring from you other unit to replacement? It is a plastic ring snapped into exaust hub.

 

[muller2357]

Re: 96 venom 200 lost SPEED

as far as i know i transfered all parts
i'm not familiar with the blw ring
where exactly does it go
do you have to drop the lower unit to access it

how would that affect top end speed if it was missing

thanks

 

[muller2357]

Re: 96 venom 200 lost SPEED

what does blw stand for