Ignition module swap for blower?
 

I have a thunder bolt V ignition on a carburated HP500,
I have heard that swapping to a V-6 mercury ignition module
will be better due to the timming curve if adding a blower.
..anyone know if a thunderbolt IV module for a V-6 with 14 deg. advance( p/n 805361T1) will work on this engine that currently has a thunderbolt V module?
Thank's,
Mike

Mike,

I don't know anything about blowers other than what I have read here. You are on the right track and someone with firsthand knowledge can confirm for you. You may want to investigate the Crane Hi6M ignition system. You can rotate a dial or so and set most any ignition curve you want as well as switch selectable retard (in case you have a load of lower octane fuel) and it has a hookup for a knock sensor. Check the classifieds.

http://64.90.9.168/cranecams/pdf/90006462a.pdf

Tim T.

I had the same question so here is the answer. You need Merc ign module #848823-2.

This is the factory module used on a 525SC motor. What you get is a 5300 rpm redline versus 5050, A total advance of 30 degrees and it brings total advance in a little sooner. Works great on my Whipplecharged 454 Mag.

Dave

Dave,
thanks but my rev limeter is 5350 right now stock......??

The Crane has an adjustable rev limit as well.

Don't take it wrong, but I don't think he wants that module (525). That motor runs a lot more total timing with a 7.5:1 compression than most blower motors. I'm guessing that you are looking at 28-32 degrees max timing and the merc v-6 module will work great for that. You will get plenty of initial timing and no rev limiter. It will wire in fine with that TBV motor. Down side that I see, is that it start's it's curve very early. and this adds to a root's surge in the idle. I don't think it's adequate above 600hp or so. Blowing an hp500 is probably going to put you above 600hp, so might as well go with the crane or msd.. I just went with locked out timing and an msd 6al and it works great. Sounds like the crane has more features though.

Brad, you are correct....525 module has too much total advance.
Thank's for the info!

MSD VV CRANE
 

ALSO MSD HAS BEEN AROUND ALOT LONGER THAN CRANE AND IS A MUCH TOUGHER PART ,YES I KNOW HUNDREDS WILL COME ON AND SAY CRANE IS ON THEIR BOAT WITH NO TROUBLE ,I KNOW THIS BUT MSD HAD BEEN AROUND SINCE THE 70'S AND HAVE BEEN USED ON WINSTON CUP ,NHRA SINCE THEN ,IF YOU MEASURE THE SPARK THE SAME WAY BOTH UNITS ARE ABOUT THE SAME IN OUTPUT !!! THE NEW DIGITIAL BOXES ARE KILLER
YOU DON'THAVE TO RUN THE MARINE BOXES AS ALL MSD'S ARE EPOXY FILLED NOW NOT LIKE THE OLDER ONES ,,,JUST MY 2 CENTS WORTH :D :D :D :D

I have 500hp with blowers with inner coolers. I tried v6 boxes but like perry said you will have over 600hp and I found out the only way to go was with the msd boxes with the retard control.I run a 40 ft boat at 5000 rpm 8lb boost runs 93 gps. The timing starts at 36 degree as rpm goes up timing falls off so at 5000 rpm I only have 28 degree. Do not have a problem of blown engines like I had with v6 boxes and I know if I really want I could go faster by running at 30 or push my luck at 34 degree. I can run all day hard and never have hi oil temps or hi water temps.

Bossman,
What kind of setup do you have? I have the MSD 6BTM ignition. I do not use the Boost Retard feature. My timing is locked in at 29 degrees.
I am running a blower with a Superchiller.
You are running 36 degrees at idle?
At what rpm are you starting to make boost?
Correct me if I'm wrong but do you have the Boost Retard set to retard the timing 1.5 degrees for every pound of boost?
Thanks, Russ

Great info guy's.....timing starts at 36 degrees..got me confused though.....? Please keep the info comming!!! :)

Yes, it is based on 1.5. I use 36 at Idle it loves timing. It makes it very nice at idle. at 3200 it starts to really give the boost. I have 250 blowers with twin 750 carbs. I also run 93 gas. I also have msd distributors.

Rich

Bossman,
This is very interesting as I am trying to optimize my engine performance at the lower rpm's.
My engine: 496" Stroker, B&M 250 with 1050 Dominator worked over by Nickerson to a 1170 cfm rating, Superchiller and
MSD 6BTM box and distributor.
Where did you get your information for your timing specs?
Are your carbs "Boost Referenced"?
What displacement are your motors?
Thanks Again, Russ

I have 509 motors started as 502-500HPs. The carbs are not boost ref. The msd control works of boost. I burn't up 4 motors playing with v6 boxes and no inner coolers. I put msd, inner coolers, changed boost up from 5 to 8 lbs. Played with the base timing to give me 28 at 5000 rpm this worked out to 1.5 just like you said. What I had before which was 32 degree at 5300 before the changes. Being able to dial in with this msd control is great, I wanted 30 or less total and got it. Before I had to play with the carbs to get it to idle good. A friend who is great with carbs took the boat out and ran it hard, stopped, checked plugs, check again and again. He changed the carb settings front and back about 20 times. ran it fat then keep changing sizes til it started to get lean then went back up. I now have over 50 hours on them set this way and not one problem. Clean plugs, clean stern and smoooooth idle. I know I have a lot more power left but I'm chicken, after 4 motors up in smoke I now have something that is turn key, it's now FUN. I had 28 bravo props after changes went to 30 that is with 1:36 gears, bravo x drives. Had one motor on dyno BEFORE CHANGES at crocketts. Got 654hp at 5200. Didn't get it done after changes but they had to make it gain even more.

Rich

Bossman, what is your static comperssion ratio, and what model MSD controller(part number please) do you have. Were your Engines Mercury factory HP500 Blue engines before the Mods?
Sounds like I might be going your way :)
Mikey

The msd ignition I have is msd 6 btm. It comes with the box, wire harness, retard controler. I had stock merc 500hp motors to start.
I only changed the heads to merlin. I sucked valves in with the stock heads, 3 times. The merlin iron heads have been great no problems of any kind, also changed the springs. I played with carbs, plugs, v8, v6 boxes everything that was going to make it run with a blower and if it could go wrong it did. When I put them together this last time and went complete msd ignition and had my friend set the carbs I now have something. Hope this helps you.

Rich

BOSSMAN,
do you feel that the stock heads are not going to work then with my set-up, running a max boost of 5PSI. Why do you think you sucked 3 valves??

My 'stock' HP motor has over 350 hrs with max of 5* boost using the T-Bolt ign w/V6 module and boost referenced 1050 dom. No problems. I tried the V8 module because of the V6 timing curve near idle. Made no idle difference on mine.

h2o, I think the real problem in my case was running 32 and 34 degree timing that did them in. This was with no inner coolers. I found that the inner coolers was the best thing I did. I was running hard before and would have hi oil temp and water not now and that is with higher boost, but lower timing. Also my motors idle at 850.

Rich

BOSSMAN & US1 Fountain, Thank's again! This info is invaluable to me!! US1Fountain, do you reccomend the V-6 module? If so, is it the 14 Degree advance module?
What is your total timing.
Do you reccomend anything else that I may be overlooking?
Thank's
Mikey

Not so much that I recommend it, but more of a factor that it works for me with good results, if not better. My motor idles fine, so I don't have to keep the rpms up to the point at which point the timing starts advancing too much. My timing is set at 28-29* at 3500. Yep, 14* module. My motor runs great with the Merc ignition. If it ain't broke...........
I personnaly didn't see the need for an aftermarket ign system for my own use.
Reasons being
a) I only run 5# boost at 29* max.
b) my idle is good, transom is spotless
c) MSD & Crane both harp on the multi spark at idle. *The following is my understanding, so read with caution* While that is great if your motor idles better that way, it is also said to be shorter hotter sparks which does wear more on the plugs. (Nit picking there I know) And also, once it goes back into the single spark mode, it is still the a shorter spark. The stock ign gives a more fatter spark throughout. I prefer this myself. Many MSD users will say no noticable difference at off idle rpm.
d) I hear of MSD failing, my brother went thru 2 MSD units in 1 yr. "I" have yet to hear of Mercs units giving out. Not saying they can't. I'd just rather not chance it. MSD distribs have a bad rap of rusting. Do a search on these 2 factors here on the board.
e) my motor is more of a bolt on blower package with well over 300 hrs and 7 yrs with nothing more than a swap to a hyd roller cam and some mild head flow work. Something must be right. Actually, the head work has cost me some power/speed.
f) power is there, and it is GREAT! :D

HOWEVER, if you were to run higher boost, the retard system that Bossman uses would be the way to go.

My motor made best power/torque at 30* on the dyno this spring. I just keep it at the 28-29* for the saftey factor.

If you are just bolting on a blower without tearing into the motor, the V6 will be fine. Just be sure to upgrade your fuel lines and every fitting, all the way to the tank, including the water/fuel seperator. Anti-siphon valve.

These are just my personnal opinions/experiences.
Sure others will be different.
Head spinning yet? :) Hope this helps more than confuses. If nothing else, print this out and line the bird cage with it. ;)

Jerry

There is some good info on this as well as other blower tech stuff in the Holley marine products catalogue.

us1 fountain, I agree with you if I would have set the timing at 28 or 29 I would still have the same heads. If you stay mild, v6 will work, it did on mine until I wanted more and I had my motor dynoed at 34 so i tried 32 thinking it was safe and got 4 hours and lost a valve. After three times I woke up and changed to what I have now.

Rich

Jerry, thank you! I am planning on 5 PSI and 29 also :)
and I will use the V-6 14 degree module as well.
thank you all for the great info!!!
Mikey

I used the v6 module on two other combinations and it worked great. I always figured, simpler is better. It was not until this motor that I found the factory ignition couldn't cut it. I can't tell you why this motor is different, other than bigger and more boost with more carb, but I tried everything, but the ignition to get the plugs to stay clean. I figured I had a carb issue and talked many times to Nickerson (he set up the carbs). Finally pulled it and put it on the dyno and right away saw 30lbs torque increase using msd vs merc. after a couple of pulls, the plugs started to clear up. 2 more degrees of timing yielded 60hp. Now the motor never thinks about fouling a plug. There must be a point when a certain volume of mixture compressed to a certain level is too much for the stock inductive ignition to ignite fully??????