Need Help Quick!!
 

Ok everyone, I need some help here. As many of you know, I have been redoing my engines over the winter. What I did was take my stock 525SC’s and replaced the blowers, carbs, pulleys, belts, etc. Prior to this I was running 88-90 with standard Bravo’s on my single step 35’ Fountain. After the new 420 mega-blowers, new carbs, belts, pulleys and nose cones on the drives were added, I’ve lost 3-5 mph. Obviously we thought it was the drives or props so we tried a 26, 28 (original), 30, and 32 pitch prop with little to no difference in any of them. We then tried 2” shorter drives because we could not get the props to blow-out getting on plane like they had been, still no change and still lower speeds. We got anywhere from 5400-6000rpm’s with then props, but nothing helped. Finally, we thought maybe the engines had a compression issue or leak, but we tested them both and they were perfect. The only thing we can think of is that we aren’t getting the horsepower we should. If so, how’s that possible? What could possibly be mismatched that would be causing this problem? Should I spend the money to have them dynoed, then find out it isn't producing the horsepower, but not know where the problem is or find out they are producing more with lower speeds? Everyone working on this is completely frustrated!! Help!!!!!!!

The dyno will eliminate the HP question and show where you should running RPM wise, however if it is pulling strong you my want to look at the nose cones, maybe try a stock set. I have heard of certain ones that have "lost" speed when adding cones. Just a thought.

We thought of that, but we tried the shorties and they did the same thing............

What did you change as far as the carbs ? Are they boost ref, and does the motor seem strong or does it lay down ?

Carbs we went to dual 850cfm. The motors run amazing, idle great and sound perfect...........

Who built the motor's??? I've had nearly the same problem with Motor builders in Kansas City myself!!! The problem being is that they might be great at building a Big Block for the Drag Strip but don't know the right combonations for Boat's (i.e. Offshore Boat's - not small jet boat's)

What cams are you running??

I'd add a Superchiller to cool the fuel, when you get a chance. Heck I've heard of people adding a "chiller" to a stock 525 and getting AWESOME results!!

They were stock 525's and the guys at Advanced Marine jjust added the new parts. It runs great.........

Advanced Marine in St. Louis???

No, at LOTO. They do work with the Bacardi Team........

You are not making as much Hp as before. Get those motors hooked up to a dyno and see.

My be the only way, just looking for ideas where the problem may be...........

What props and rpm were you running before?

What were you using to measure speed, GPS?

With same props, drives and slippage, at the same RPM, I would think you would duplicate the same speed regardless of max horsepower :confused:

28 pitch at 5800rpms

GPS

Exactly!!!!!

DYNO
 

Also, you did not mention a cam change.
What PSI are the blowers set to?

If using the same cam, well your not pushing any more air/gas through.

You have to dyno to find the results, one engine should do.

Wannabe

We did not change the cam because we felt it wasn't necessary wth the motor already being set up for a blower. We have locked the timing on the engines and we are running 5lbs of boost.

Why do you say we aren't pushing more air? Bigger blowers, larger fuel line, larger carbs, how couldn't we be?

You think 1 engine is safe?

Are you pulling more RPM's??

I would think a cam change would be needed with such a big change in Blower volume.

But, heck I'm just a undertaker:cool:

B&M used to have a comparision chart that showed with nothing more than a blower change on the 525's and a few hundred rpm would result in 700-750 hp. i would be looking at timing. you must be using an aftermarket ignition system in order to get the rpm's up to 5800 as mention above. i would think nothing else changed with drives and props you should have been all over 5800, meaning you should of had to add 2-4 pitch sizes. good luck and let us know the results

later

We've gone from 5200 to 6000rpm's with different props.

Why do you think we need to do a can change. Is the blower that much different?

I appreciate the help, keep it coming!!!

Matt still has the boat and he's been more than helpful. That group over there is amazing. We are looking at the MSD box now because it has some technology in it that allows it to retard the timing depnding on the boost. We thought we had bypassed it by locking the timing at 34, but we may not have been totally successful. Does anyone have experience with this type of MSD boxes?

TTT


Sorry, just need help. Want to boat this summer...............

1) My personal opinion is get rid of the MSD ignition, if the engine is properly tuned, you don't need it. I don't have it on my old 900's (572 cid/w2 750 HOLLEY'S) and I don't have it on my new 1000's (615 cid/w2 750 HOLLEY'S).

2) You are over carburated/jetted. Today I wittnessed Tommy @ CHIEF ENGINES get another 90 hp out of an engine by just properly jetting the carburators.

The best money you will spend is to put BOTH engines on the dyno and set them up properly. If there's no one in the area, create them up and send 'em on down and we'll be glad to look at them for you. Call Tommy first to check the schedule.

Robert

What PSI did the stock blowers run ?
If you ran 5 psi on a small blower turning it fast , and 5 psi on a big blower turning it slow , you didn't really change anything . The only advantage would be less heat build up . If you don't change the heads or the cam or the cubic inch , you are not getting more volume in . Pressure is pressure if all else is the same . Adding more carb to the same mix may have just screwed up the air fuel ratio . Also 34 degrees is too much for blowers in offshore boats . You may be detonating ,slowing it down ..... Just my .02

Good luck !

Bingo
5 psi is 5 psi wether its a little Weiand or a Ginormous 14-71

Smaller top pulley time crank her up to 7 or 8 PSI with a 420 you will not generate as much heat pushing thos psi's as you Weiand. That engine only has 7.5:1 comp ratio wich is conservative.

Just with my very numble opinion with my very limited engine knowledge

How was it tuned to begin with? I'll bet you're running way fat and if you are it could easily cost you 90hp (as mentioned above).

If pulling the engines and sending them to a dyno is not an option then what about welding a bung in the exhaust for a wide band 02 sensor? Does anyone else use a wide band in the boat to tune? I haven't seen it before in a boat. Is that not really an option in the boat? I'm not sure where in the exhaust you'd have to put it. This may be a much less expensive option than pulling the engines. You can get a great wide band for around $700. Where are you located. I didn't look. If you're near Dallas I can loan you mine. You can weld in a couple of 02 bungs for $20 and find out what it is doing. I'll bet your A/F is way off.

You may also have too much timing. Retarding it may get you a few extra HP but won't make the difference you're looking at. The A/F ration may. Tune it. A proper tuning can easily be worth 100hp on a forced induction application.

I would, however, respectfully disagree that 5psi is 5psi. Pressure (boost) and volume are inversely related. Increase volume and you loose boost. I've seen a large volume centrigugal supercharger (Paxton Novi) make 60 hp more than a small volume (Powerdyne) supercharger with both at 10psi and no other changes. Increase volume without loosing boost and you will increase power. All boost is not created equal.

Wide Band?
 

TTT - I am still curious to see if anyone has a wide band 02 bung in their boat exhaust and if so where it was mounted. Is this feasible? I guess on a dry exhaust it certainly would be. Just curious. I'd love to be able to hook mine up to my wide band.