Blower Motor Set up and Tune 257 Mirage
 

Hi everyone ,

Im new to this forum and am looking for help. I actualy own a Hot Rod shop in California www.westcoastautocraft.com and have really good knowledge of engine building and tuning. I have zero experience with blown engines or boats.

I purchased a Mirage 257 trovare with a blown 502. First time out blew head gasket. I had a shop go back through it and now im just getting it going. The shop who has been working on it has done a great job and supplied me with a ton of goodies. Now i just need to make it all work and im a little lost.

What i know about the set up.

502 shortblock with a pretty big hydralic roller blower cam (dont know the specs)
Flat top forged pistons
Everything from here down is brand new.
Dart Pro 1 heads 3 with Dielectric Coating
B&M megablower all rebuilt at The Blowershop with thier front snout and drive. 20% overdriven (should be 6-8lbs boost)
Intercooler with sand strainer
Hardin Marine max volt distributor
Daytona CD-1 Marine unit and coil (running the mercury marine HP800SC program)
Hardin Marine "Hurricane exhaust system"
Quickfuel Marine Carburetors
Holly blue pump regulated to 7lbs pressure
Bravo XR drive
Signature 4 blade 28 pitch prop


So i want to start by saying that i have no issue with any of the mechanics work. He was not quite finished when i went and picked it up. Its been there a long time and i just offered to finish it myself. The day i got there he had just got it running for the first time and it needs tuning. When he started it it was backfiring through exhaust pretty bad. Then he realized that the box was advancing as well as the distributor. Because i was pressing him to let me take it he safety wired the advance in place which stopped the backfiring.

So i finished up a few odds and ends and took it out yesterday. Idle sounds great, throttle responce is excellent with no pauses or stumbles, and boat starts right up. The problem was the minuet i put load on it it has no power and sounds like its stumbling nd or missing. It is maintaining 7lbs of fuel pressure. I put a timing light on it and at idle (800-1100 surging) the initial timing was bouncing around between 13-18 degrees. I figured the bouncing seemed to be from the surging. The advance is all in around 3500 rpms at 28 degres total. I dont know what it should be. Thinking about the timing bouncing i decided to pull cap and check the mechanical advance, and as it turns out the rotor does move a few degrees. There are no wieghts or springs and it is wire tied, but the tie job seems to have loosened a bit. One other thing to note is it also dawned on me that the full tank of fuel is exactly 1 year old (91 octane from pump) and the fuel has been in the boat tank and the boat has always been indoors.


So based on my own knowledge (with naturally asperates engines) locking out the distributor in a more appropriate way and getting better fuel is in order.

Here are my questions.
Do you think the slightly loose wire tie job is causing the problem?
Can the fuel cause this problem?
What timing advance/set up should i run (initial, advance, how much, and how soon?)
Do you see any holes in my set up?
What is the top speed potential of this set up?


Any good advise would really help!

Thank you all in advance.

Chris

Did you change the fuel filter? Wouldnt think year old fuel would cause any issues unless contaminated with water which is unlikely. Also check the fuel tank vent. Just some initial basics to check. The wire tie job might not be relevant but fix it anyways. Hopefully some others will chime in. Congrats on the Mirage, very well made capable boats made in the Seattle area( no longer in business). I am building and modernizing a 93 232 trovare. Timeless design.

Is it ethanol fuel? If so drain it and put fresh gas, it has caused more issues than I've ever imagined. Even with the distributor moving the timing 5* you're still only at 33* total, which is where you will probably need to be anyway.
Air/fuel ratio gauge would be really helpful. With the 420 blower. (I'm assuming) 20% overdriven is a decent amount and may be pulling the power valves open a bit early if they are not boost referenced. Just a thought.
But before getting into any of that definitely drain the tank or try a seperate fuel source, 5 gallon outboard can or some sort.

Yes, all new filter, vent, etc. i agree, i love the design.

Im going to drain fuel today. The carburetors are boost referenced.

Update.

I locked destrubutor as per Hardin Marines proceedure. I ran it again, same thing. We started advancing the distributor and the more we advance it the better it runs, but it would be off the chart (like 50*) so we abandoned this. We locked the advance all together and set it at 30*, and it is popping out the exhaust pipes.

Any thoughts?

Try running a stock Mercruiser dist with the V6 module(less advance).. If it runs well after that you found the problem.. In my limited experience I have found aftermarket ignitions are hit or miss on marine engines..
Get a wideband O2 gauge/sensor for the boat,, personally I dont run any boosted engine without one..
Next running 6-8lbs of boost on a 500cube engine with big heads and cam like you have is pushing that blower..
I wouldnt safely run that B&M blower past 5lbs of boost on you engine setup for any length of time..

Make 100% sure you are on the correct mark on the balancer. I've made this mistake before, if you're on the wrong mark the light will show roughly 45-50* when it starts to run right. In all reality you're at 15 or so degrees.

if your distributor is locked out, you can set the engine timing by simply cranking the engine over, no fuel, just ignition, this will give u a correct and consistant reading to get you in the ball park, by doing this you will be eliminating fluctuation of irratic idle, cam movement, chain flex etc... 30 deg BTDC is a good place to start, once you have fuel system dialed in you should be safe up to 34 deg...

have you checked the plug wires to make sure they are in the right order,sometimes people will overlook the simple things.i try to follow a satement i heard a long time ago KISS, [ keep it simple stupid],it works for me.

I've had bad balancers before that made you think it was timed right but it was not. You might try using a vacuum gage to time it and see what that tells you.

Already checked this. The mark is perfect.

Thats a great idea. Whats the best way to insure no fuel?

Yea, in the same way. Thus was the first thing i checked.

Shut the pump off and drain the bowls

Not to sound stupid, do I just pull one of the bottom bolts that hold the bowls to drain them?

*****Update*****

I called Chris at Daytona Sensor. He is their "technical guy". What as arse hole! I don't think I have every talked to anyone more condescending in my life. He basically said that everyone involved in my boat project is an idot (including me) and we need to pull the engine out and start over. He did not get any info from me other than "did the engine builder tune everything on the dyno?". I said no, and he said "it is impossible to tune a high performance engine of any kind in any environment than a dyno". Well I guess i have gotten lucky on my 8 second Camaro that I have been running for 15 years. The other thing he said is that you can not make anything other than crank trigger work in this application. He really put me over the edge when he said "look, I am not in business of talking to anyone over the phone except professional engine builders. You are wasting my time and if you are not willing to send the engine to a professional I would rather you not run my product"

So the Daytona is on its way back to CP Performance and I am installing a Hardin Max Spark Box.

*****Update*****

Pulled the distributor and the shaft is bent! Like really bent. The rotor wobbles around like crazy when I spin it. Might be my problem. I have my parts guy driving to CP Performance in Rhonert Park and picking up a New distributor, Ignition box, and coil. I am going to stay late and install it all. I will report when I am finished. Since I am **** canning that Daytona box (read previous post) I will just curve the distributor the old fashion way with springs and bushings. Any thoughts on what curve I should set up?

10-12* max advance curve total 32-34 all in before 3,000 and yes just pull a lower bowl screw out to drain the bowls.

I was actually wondering if the distributor needed to be phased similar to when you use the Merc hall effect distributor.
Have a friend that could not get engines to run with his HI-6M's. (similar to Daytona's) Exact same symptoms you are encountering. He did not have the rotors phased
to run with the ignition boxes. Just like the rotors that Daytona Sensors sells to hook up the CD-1 to a Merc distributor.

Part # 103004 Marine Rotor (required for correct phasing of CD-1 Marine applications using Mercury Marine Hall effect distributor). $24.50
http://www.daytona-sensors.com/CD1.html

Glad you're dumping their product if that is the way they treated to you.

Yea, we just ran to CP Perfornance and they swapped everything out no questions asked. They are such a great company (CP) and i know they own Hardin Marine so i am going to run thier whole system.

So when you say max advance of 10-12 if im reading you right my initial timing should be between 22-26? Or are you saying initial should be 10-12 and total 32-34 before 3k?

I just want to make I'm reading you right.

20 - 22 initial and 10-12* mechanical advance. Total being 32-34* depending on your plug heat range, fuel, and of course how the plugs look after a wot run.

****Update****

Things i have done

Changed out Datona Box for hardin Max Volt
Changed Hardin Marine dustributor twice (both units i recieved from them were junk) for MSD Marine
Jetted carbs
Locked out distributor advace
Set time to 32*


Boat is running good now. 79 GPS at 4900 rpm. Time to reprop. Im running a 28p. Any suggestions?

Go to NWoffshore.com and find a member there (Thunderballs) he has one of the fastest mirage 257's around and has done extensive work and research regarding the 257 specifically. It's not a hull designed to go 90(he had to mod his hull for added power). Great guy and very knowledgable on the Mirage line. Great boats but like I mentioned its tough to get them above 80. Good luck with your project.