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.

What kind of power will i see out of my motors with the 250 blowers and 850 single carbs? I want to take it easy on my trs drives but i only boat on a small lake so i won't be "airing it out" on big water. There is a pair of 250's in the classifieds but i will need the single carb adapters and maybe a different crank pulley?

I had a 84, 38 Cig years ago that had 420's. I changed heads to merlin cast irons , changed cam , bolted on bm 250's with single 850's boost referenced , msd ing, stainless marine exhaust and ran 5 lbs of boost. This set up made about 575-600 hp and pushed the cig to 72-73 mph . I also ran trs drives . I would get about 150 hrs on drives before they would need to be gone through. I would go through drives before they blow due possibilty of losing a gear case..These motors had about 600hrs on them when I sold the boat.. They are very reliable if set up right. Tom

the weiand's work very well I did one of those engines this season, any way the marine blower(blower itself the same) gives you the special thermostat housing, 10 rib belt, and one of 2 different lower crank pulleys depending on if you have a aluminum or steel lower crank pulley. power wise my 489 with that blower, ported 781 oval ported heads, 8-1 comp, comp blower cam, made 525 @ 5500 4psi, 610 @ 5500 6-7 psi...you will need to boost referance the carb and rejet...Rob

as for boost referencing, what will need to be done to my 850's in order to work properly with the 250 blowers?