682gold

iTrader: (3)

I have read numerous post on this but would like to have answers on my thread. I have 525sc's. One has been completely rebuilt and the other will be freshened to match the rebuilt one at the end of the 2014 season. It has the stock 177's on them and I am looking to get more power for more speed. Want to keep the engines as reliable as possible. What size, brand blower with what intercooler should I go with? Do I need an intercooler with a larger blower? Like I said I have read that a lot of you have had good experience with this.

MILD THUNDER

iTrader: (3)

The idea of a larger blower, is less heat per pound of boost. On a 525SC, there are a lot of ways to pick up power. The old flat tappet cams leave a lot to be desired, the cylinder heads are fair at best, very low compression, and the little blowers are heat pumps.

A hydraulic roller cam upgrade, and bolting on a blower like an 8-71, B&M 420 Megablower, or even 6-71, would be a huge improvement. I have hopped up 454's with Dart heads, hyd roller cams, with 420 B&M blowers. To make 6psi on my engines, the blowers are currently underdriven 7 percent. They made 804HP at 6200RPM. Although I have never increased the boost levels from the 5-7psi range, my boat is much faster with the larger blowers, and engines haven't changed their recipe. (had 177s and 250 blowers before on these engines)

By upgrading to the blowers I mentioned, you will gain reliability from a cooler air charge, along with more power. The air temp change from a small blower 100% overdriven, to a larger blower underdriven, is huge. Plus the blower itself will live longer. The small blowers like the 177s, were originally meant for mild street driven cars and tow vehicles, and they work well for that. However, in a marine application, here sustained high rpm is the norm, the larger blower is the way to go.

By going with a better designed camshaft say from Bob Madera, and a 871 or 420 blower, a little more max rpm, it will feel like you dropped a completely new set of bigger engines in the boat.

MILD THUNDER

iTrader: (3)

Key things are a blowers efficiency . Generally speaking, roots blowers are not an efficient design. Now, to complile that issue, a SMALL roots blower, even becomes more inefficient. In a way, I feel an intercooler on a 177 blower, is kind of like a band aid. Your trying to cool a very high discharge temp, down to a level where a power increase or drop in air temp is acceptable. Now, with a whipple, or even a larger roots, your not making that high discharge temp ( at most boost levels we run), and adding a intercooler even helps more. I don't think adding a intercooler to a 177 will get anywhere near ambient air temperature. The intercooler would have to be unrealistically efficient. Now, with a screw blower like a whipple, or any compressor with low discharge temps with a good intercooler, achieving ambient or even below ambient in some cases, is attainable. That is pretty much why, pound for pound, a whipple would stomp all over a 177 roots blower in power output, and safety factor from detonation. With a large blower say underdriven roots, going from 5 to say 7psi, doesn't heat the air charge up that much more. But, going from 5-7psi on a small roots that's already highly overdriven, can have tremendous increase in air temp, once the blower gets driven beyond its efficiency.

This summer, a buddy and me, will be recording actual manifold temperatures while out on the lake running. The results should be interesting. Especially when we do before and after intercooler installation.

682gold

iTrader: (3)

Who made the 177's for merc? Also if I go to a larger blower will I be able to use the existing intake and carbs that came on that motor?

MILD THUNDER

iTrader: (3)

Weiand made the blower. No on the intake and carb . But typically a used blower package will come with all that. Dual carbs doesn't necessarily mean worse fuel consumption.

Crude Intentions

iTrader: (1)

Great info joe. Here's what I'm wondering. If the motor is built and tuned right. Barring any catastrophic failure how often do you need to go into the bottom end for a freshen?

Not like a 1075 but something like you have.

MILD THUNDER

iTrader: (3)

Bottom end should last a long time. Really not any less than not having a blower . Providing it's tuned right and not washing the cylinders and oil down with fuel.

mike tkach

iTrader: (3)

i had a boat with a pair of sc525s,when i bought it the provoius owner had installed a crane 731 cam and dart iorn eagle heads,i finished the job by adding 8.71s.i set it up with 7 lbs boost and i ran the snot out of it.i got tired of replacing bearings in the 177 blowers.