420trs Blower upgrade
 

Well so far i've had two trouble free seasons on my rebuilt 420's. 50 hrs on each motor to be exact. Trimmed out for speed in ideal conditions i'm right around 71 mph gps in my 311, fairly respectable for an old tug but not fast enough. I am wanting to install the weiand 177 blower kit on both engines to create a 525 sc. I know my motors have slightly higher compression than factory 525 sc's but i'm not looking to run very much boost. Is there anything else i will need for the install? I'm hoping that my factory carbs will work with the blower kits, they are 850 cfm i believe. I have already upgraded the exhaust to imco's with the long tails for the trs application. Any info on this upgrade would be very helpful! If you guys could point me in the right direction as to where to purchase the blower kits that would be appreciated, i am in central, il:ernaehrung004:

how many hrs on your engines. sounds like your in the same boat as i was about 8 or 9 years ago.

Just convert it to XR Bravos and u gain 10 MPH without blowers.

Maybe have to go thru the XR's once a year but cheaper in the longrun ,less stress on the engines and easy fix .

I added B&M 174 blowers to my 420's, 4psi boost for 5 seasons on issues whatsoever. Make sure you have inconel exhaust valves and severe duty intakes.

You ment "no issues" right ????? sorry:grinser010:

The old Hawk 525's were a 420 merc 8.5:1 with a 177 blower, and 800 or 850 carbs. The merc 525SC had 7.5:1 and 1050 carbs.

Both setups were reliable. I have a similar setup, but bigger roller cams, and aluminum heads, and they push my 14k lb 402 Formula with TRS to 72 on GPS. They run great and sound cool with the little blowers.

Thanks

I have approximately 50 hrs on the rebuilt motors. Is there any difference between the marine blower kits from weiand vs. the standard kit? I noticed the kits on all the performance boating sites have 10 rib pulleys vs. the 7 rib. Any other differences? I would really like to reuse my 850 cfm carbs, but i know they will have to be tuned for the blower

That's movin for a boat of that size! Kinda makes me think 80 mph might be obtainable with the little blowers

get your self some bm 250's ,( a little larger blower than the 177) you can run one 850 or a one dominator or two 750's. You should always use a larger blower when possible. You can spin that larger
blower slower and create less heat... also, you can use the larger
blower down the road if you choose to make more power.