Put slightly smaller blower pulleys on and belts started slipping at full throttle. Weiand 177's with serpintine belts. lost a little spring tension. How keep from slipping or increase tension?

How many ribs are your belts? Did you adjust it according to spec?

Are they 10 rib belts on 525sc's?????

If so you can get a shorter belt at Napa for around $40.

Yes, on the SC's they are 10, I was wondering if he has a 6 rib automotive setup???

Spray track bite on your belt.....

I have a smaller pulley on my 525sc. I'm not sure if the belt is shorter than stock or not. The Napa part # is 100540. I start to get some belt slippage around 75-100hrs on a belt and you can see the grooves are worn.

As far as I know there is no way to adjust the tension. Its a spring loaded tensioner pulley.

Yep, you're right. I was thinking of the adjutment on my 420 and looked at my 177 with the spring. Try a new belt..... Where is the tensioner indicator???? Is it close to the end or in the middle?

Yes I belive they are the 10 rib from the 525sc's. Griff how much shorter are the napa's? I will try them.I have 150hrs on current belts. I am not at the end of the tension spring. Griff, BTW I had 625's built last year using original 525's. Very happy with them. Torgue and power curves perfect.

I don't know how much, if any shorter they are. The smaller pulley has been on since I've had the boat. It had a Gates belt on it when I got it. Napa uses the same numbering system as Gates.
I can tell you that when mine started slipping and I got a new belt, it was obvious that the belt grooves were worn.

BTW, what are the details of your 525sc build up to the 625hp???????

BTW, what are the details of your 525sc build up to the 625hp???????[/QUOTE]


460's, Dart Iron eagle cast heads, Full roller comp cam (mild lift and duration but larger than stock) ,JE pistons/rods etc. 8.25 comp (still had to cut pulleys to get back to 6lbs boost, was getting 4 lbs even with the comp bumped to 8.25 from 7.5) Tuned at Zul's @ 625hp with 5.5 lbs boost and 650 with 7lbs @5,500.

600+ ft lbs torque comes on real early and stays flat througout entire rpm.

pulled heads after 150 hrs and looked great with no signs of reversion. They never load up in no wake zones and idle real smooth.

Also changed out the Crane gold rockers for the new style Crane gold with thrush washers after a roller rockerneedle bering came loose. kept the original mech fuel pumps but aded electric assist boost referenced at 4lbs boost.