Blower help, ideas
 

As some of you know I have installed my 250 blower on my HP500..I took it for a test run today... Stock I ran a 24 Bravo1 labbed at 5100rpm about 62mph...I now have a 250 b&m with twin 750 holleys and have a 26P bravo1..I ran about 63mph and 4600rpm..... I am not sure where my problem is yet..I kinda think I am not making any boost...my setup is supposed to be @ 4.5psi..I wonder if I may not have my belt adjusted correctly..I plan on getting a boost gauge on it Saturday....it seems to have something in the mid throttle but it falls off at about 60mph now....also, if I rev up the motor, it has a dead spot before it revs up...I am sure the fuel supply is adequate because I opened it all up....I will know more tomrrow after I get the boost gauge installed..but any ideas..

Anyone have the instructions for adjusting the belt? Thanks

What changes did you do or make to the ignition? as in advance curve and timing adjustment.
Also, what size carbs are those and whats in them for power valves, jets on the primary and secondary circuts?

Not sure on the power valves or jets..but the guys at Performance marine..Chip & Jeff..said the carbs are ready to use on my application...the timing was done by my mechanic..the way Chip and Jeff said to..

That doesn't mean either one of them was correct.

You need to find out what you have now in order to make changes. You should be making 600+hp and be able to spin the 26" prop. I would also get fuel pressure guage to make sure its not falling off in the upper rpms. You need to take plug readings after a WOT run.

I hear that bs all the time....There is no such thing as a ready to run carberator especially in a blown application. You need to have someone who knows what they are doing adjust your timing and tune your carbs....

Agreed!! You never should have run the boat without a fuel pressure and boost guage. What was done to the fuel system to supply much needed extra fuel? What size are your fuel lines? More important, what size is the pick-up tube in the fuel tank? Not enough and too much fuel both can damage the motor. Timing is also critical

Keep us posted, courious to here what is going on.

According to Nickerson, adjust the belt tensioner to show about half inch to 5/8 of the chrome idler shaft for correct tension on the blower belt.

OK, let me throw more out there....
Boost gauge is a must, you need to know how much boost its making to know if its enough or too much.
I would put the 24's back on and see how much more speed and rpm you get with the new induction...that should at least tell you if your making more power and if so how much more. Changing too much all at once is like trying to hit a moving target, you loose the baseline figure that way.
If you still have your stock 500HP module (P/N 17316A 1) with 20*of advance in the ignition system, then set your total advance to 30*@3200rpm...that will keep it safe for now.
You should be running colder plugs also...The stock AC MR43T's should be replaced with the MR41T's.
Carbs...
What size and model # are they?

Sounds like you have something wrong. I have a B&M 250 on my 502, here is my basic setup on my Force 235.

Timing 30 degrees total with a base of 10
Carb by Nickerson, single 1050 reworked to something.
Belt with 5/8 showing on tension rod
AZ 120 thermostat, crossover with small bleed holes to headers when stat closed. Water temp (measured just at port forward fitting of manifold) 120 at cruise 125 WOT. Never varies from 40 to 85 degree water.
Water pressure 15 to 20 depending on water temp and speed
AC MR41 plugs
Holley Black fuel pump, no check valve, 9 psi at WOT
3x21 oil cooler with Mocal T-stat. Temp gauge in pan, 180 at 3000, 200 at 3500, 235 at WOT

Boost gauge generally shows 1 lb. vacuum around 3000 and builds gradually to 4 to 5 from there. If your belt was slipping I think you would smell it. From your numbers I would not run it further until you determine where the power is being lost. Might be lean or else the rotors are not sealing well enough to make any boost. Not sure where you should start checking but get someone to assist that does. I believe you only get one shot to do it wrong with a blower motor.

Keep us posted as to what you find but I would start with doing some plug readings from 3000 up at 500 rpm intervals. Check fuel pressure while running and get that boost gauge on there. Check timing from idle to 3K and up.

You should be running about 76 to 78 with that setup.
Force 235
stock 330 56 to 58
stock 502 415 hp 64 to 66
502 w/headers and single plane dart 67 to 69
502 w/B&M 250 at 5 psi 78 to 80

My 235 did not like the 4 blade prop, lifted the stern too much. The best prop for the 235 seems to be the Mirage Plus. I still have issues with bow lift. The faster you go the more the nose plants. Scrubbing a lot of speed off. BudMan shaved the hooks off his and it did not seem to make much difference but he is only running 60. Once I get over 65 you can fell the nose dropping as you add throttle. You have to over trim a bit to get the bow to carry and then feed some throttle in. Once you get the bow up drop the trim a touch to hook the prop back up and feed it more throttle to 75. At that point over trim a touch and rock the wheel slightly to Starboard and back to straight, this seems to put it up on what little pad the hull has. Once up on the pad it will wind out to 80. That hull was not meant to go over 65 or so. I think I can avoid all that trimming nonsense with the right prop but I have not addressed that yet. Might just have to change the address of the hull to fix it.

Ok guys...here is where I am at now.... I added all the guages and took her for a test...fuel pressure runs about 7 constant, sometimes a bit more or abit less but basically 7..boost is mostly vacuum until wide open then I make about 1 psi...I have the 4" pulley....I am just not making any boost with that pulley setup..I need a 3.34 and I should be around 5-6 psi...here is my problem..my blower is the older model b&m so it has the older shaft in it...The older b&m blowers have a 2" shaft that has about half of it splined, the pulleys I have are not as deep as the earlier b&m pulleys...I need either a 3" or 3.34" older style b&m pulley..I can post a picture later...but anyway, that seems to be my problem..just no boost yet..timing is about 32*..boat runs strong even without boost..Can't wait to get some boost on this bad boy! should be a screamer!...thanks for all the help guys...it will most likely be a few days before I get a pulley but I will let you know how it goes...I may have to replace the shaft if I cannot find an older style pulley..that would be a huge bummer..

also, thanks for the heads up BadDog, I will keep all that in mind when I get her running right

Someone correct me if I am wrong but generally retarding timing increases exhast valve temps. With that being said if you have good exhaust valves you may want to back that timing down a tad. Nickerson recommends 29 or 30. The B&M 250 marine installation manual recommends 28 to 30 max. Might start there and see how it runs after you get your boost back.

The chart in the manual list several part numbers of different diameter pulleys. The smallest amount of boost (4 to 5) list one part number with others going 9 to 10 psi. You may want to check the rotors and see if perhaps there is excessive clearance. I would suspect you should see more than 1 pound even with the largest pulley.

Well, we suspect this blower setup was on a much smaller engine..(310hp 454 or something) ..so when you take that setup and install it on my HP500 that has been massaged already..it just doesn't make any boost for it.... I need a B&M part# 155193 3.34" pulley or a 155192 3" pulley ... I would prefur the 3.34" as it should make me a subtle 5-6 psi..but like I said those are older part #'s that get superseeded to the newer stuff...so I may have to replace the shaft...but we will see..

btw, the clearances on my teflon were fine..so no probs there

Thats great info for you with what Bad Dog has experienced on his set up.
Bajapred...You said you worked the 500 a bit? What cam did you use?

I dropped a valve after I bought my 500 so I rebuilt it to a 509..kept the same cam & valve sizes but ported the heads..i guess I am running about 525hp or so...also it has the CMI headers on it now in place of the Gils...this blower should make me close to 700hp with 5-6 psi boost... If anyone has any ideas on finding the older pulleys that I need please let me know...

Give us the cam specs and the compression ratio.....

Well, the cam specs are the same as a stock HP500..the compression should be around 9:1....stock they are 8.75:1 and with the little bigger bore I figure 9:1

BADDOG, do you have an update on your prop? I have the same boat force 235 with a 700hp/572 and run a 4 blade 24 pitch on it. Today it did 70mph on 5500rpm. Do you think a 27 mirage plus would be too much?

I run a 4 blade 26 bravo 1.. you should be able to run a 26 4 blade or a 27 3 blade easy...I still have my knock sensor hooked up..when I am at wide open throttle it is pulling my timing back a little, but I like the safety feature there..I am guessing if I unhooked my Knock sensor I would run around 70mph GPS...now I am right at 65...before I went back to my V8 module I had the V6 module and no knock sensor, I ran 68mph and was not wide open yet..so I know it would do 70 at least...mine actually idles better with my original V8 setup as opposed to the V6 module...my boat is very dock friendly right now...I still need to tune a little on the carbs, but I am reeeaaal close right now......... I know alot of you read about all my problems I had with this blower install..but in a nutshell..my problem was my water pressure..kept blowing my intake manifold gaskets..finally spun a bearing & now I have a brand new engine again!...but I love it!

the HP500 carb cam was a hyd roller, 222/230 110 .576/.598

I have the same boat(89 23'5 force) .I have a n/a 509 with a 24- 4 blade hydromotive. Im doing 69(gps) at 5100

Baddog
Im looking at putting a 250 on mine. Did you have to modify the hatch or back seat?

Have not played with any other props. Still running the stock 27 MP. Might have it tweaked for more bow lift but for now it is fine.

Yes, you will have to make a small cutout behind the rear seat to clear the blower snout. Back seat then gets a tad cut off the rear edge and upholstery re stapled. Not a big deal. You also need to shave the lip of the rear seat support to clear the blower case. Very easy to do with a dremmel tool.

I will see if I can get some pics up.

I cut a small slot in my back seat for the blower snout, but I really diod not need it..on my setup there is no need to do anything to the (seat) because it does not fit all the way back to the support ( where the slot is)...I had to knotch out the inside a little too where my carb linkage is, but in all it was about 15 minutes with the dremmel tool..but still a very tight fit..I will be down at the boat this Thursday, I will take some pics and post them on Friday night. My boat is a 26' 6" 265 Force, but I think they were the same as the 235's from the windshield back...my boat has the teak external swim platform, so that could have made a difference somehow..and I also have zero effort controls..those were the two biggest differences I see in most of the late 80 early 90 models......I also have the Power Boat mag from their first test on the 265 back in 1987..it is in prestine condition...shows my boat running 53mph with 454 330 hp..& 54-55 mph with twin small blocks...best thing about that mag is they have alot of other boats tested, a twin engine, twin turbo Fountain is one of the coolest I have ever seen..it looks bad ass!

That would be great if you guys can put up pics.Thanks
Are you guys running the 3"belt?
Just looks like there is not to much room to add a blower crank pulley.
Did you guys have to cut the hatch on the inside?

I already put in a bigger fuel pick up and lines from the tank and a return. I take it you guys did that to.

Yes, I did all the fuel line upgrading stuff..no, no need to cut the hatch at all & there is plenty of room for the lower pully to bolt on..3" serp belt is what I have..you can see the engine in a picture above in this thread..I just did not have the seat pushed back yet..you have to use 8" or less flame arrestors or they will hit the seat back...mine are 8" dia & I have about 3/8" clearance

What did you guys do for the thermostat housing?
Looks like no brackets/acc.s have to be moved for idler?

Well, not sure what you mean exactly..you use a different intake for the 250 B&M..it has the idler bolted to it along with the t-stat housing..do not run stat though....that is the problem I had...too much water pressure kept blowing out intake gaskets...

Here are the pics I promised!Send me a PM with your email and I can send you more pics if you need some...as you can see, there is plenty of room for the bottom pulley...

Did you ever find the pullies you were looking for? I have some old style 250 B & M ones.
John B

Thanks for the pic.
Did you install the crank pulley while the engine was in the boat?

I didn't look close enough at the previous pictures to see the idler came of the intake.

I installed a different shaft so I could use th enew style pullies............. you can see the dler in the picture above, it bolts to the intake and points straight out, the tsat housing is under it..look at some pictures on th net...here are a few more pics....