Reply With Quoteyou could always supercharge
Thanks for the info on the stern jack! As far as the 500-600 HP I would suggest talking to a engine re-builder. I'm sure their must be some on this forum. It can be done, it would cost some money, but not as much as you would think.
I checked out E-Bay, thanks again!
you could always supercharge
chillin,A few months back I asked a friend in the boat business (certified Merc station) about stern jacks.He showed me a Mercruiser memo pertaining to the subject.Seeing as how you have a bravo you might want to contact a Merc factory rep.They have some interesting observations about putting one on against thier gimbel housing.just my 02...
OK, I have some new info. First off I've owned ski boats in the past, this is the first Hi-pro for me. I decided 2 years ago I wanted a loud faster boat, so I bought this one from a one owner.
I contacted him yesterday and asked him why no one believes this thing runs 63 mph. He says it used to run 68, he also says that they don't normally run 63 stock, but the reason it does is because it has a stern jack on it. Lucky me!
He also said when he sold it to me he took off the Mirage 23 prop and the K&N air filter and sold it to someone else. He told me to go borrow a 23 and since I want to build the motor to go buy the K&N filter and try that out. Go figure, I didn't know that was a S-Jack, I just thought it was part of the outdrive.
He says 75 mph is very easy to get. He suggested, MSD..6AL ignition, 750 Holley,108 or 110 centerline cam with a 630 to 650 lift, Dual plane intake, and after market Hi-perf.oval heads, along with 9.5:1 pistons. He thinks that will take it over 75 a little bit. Says I could always upgrade exhaust but would wait and do that last if needed. He thinks I might have to move up to a 25 prop though as to not run motor over 5000 rpms.
Just his thoughts though. This is a good forum, I've gained lots of knowledge here from very good people.
I can't wait to hear what everyone has to say now, but I guess a S-Jack alone would make it run 63mph. Later!
Originally posted by Chillin The Most:
OK, I have some new info.
he also says that they don't normally run 63 stock, but the reason it does is because it has a stern jack on it. Lucky me!
He says 75 mph is very easy to get. He suggested, MSD..6AL ignition, 750 Holley,108 or 110 centerline cam with a 630 to 650 lift, Dual plane intake, and after market Hi-perf.oval heads, along with 9.5:1 pistons. He thinks that will take it over 75 a little bit. Says I could always upgrade exhaust but would wait and do that last if needed.
Chillen the previous owner has given some good info as have many others who posted here. Since your soliciting opinions here is mine.
First you won't need new pistons as the aftermarket oval port heads will probably have 110cc combustion chambers. This will net you about 9.7:1 with the pistons you have.
You will need the aftermarket ignition as you are right against the rev limiter built in to the Thunderbolt V ignition.
The lift he reccomended is a tad high I would look more around .610 and to avoid exhaust reversion I would keep the centerline around 112. A hydraulic roller will reduce oil temps as well.
I seen no mention of a roller rocker set-up but you should include that. This will also reduce oil temps.
I agree with Hulshot get a good dual plane intake such as Edlebrocks Performer RPM. This intake will work good to 6000 RPM and will build more torque which is what you need.
As someone else already stated the Sternjack does add more leverage to your gimbal housing/bearing and it is very expensive to rebuild. Adding this much more power and speed will further stress this situation. You will after these modifications seriously have to look at an external steering system.
A single ram set-up would do for safety concerns but does little to alieveate the wear on the gimbal bearing. A duel ram system will take care of that. So plan on spending another $2500.00 to do it right.
Ray,
Your sure are right, lots of good advice and options here.
Glad to hear from you, heard quite alot about you on this site (all good)
Ok, I agree about the dual plane edlebrock, but would you use the 750 holley with that or use a Edlebrock carb?
What is your opinion on the edlebrock dominater intake and carb Vs.edlebrock performer rpm
Originally posted by Chillin The Most:
Ray,
Ok, I agree about the dual plane edlebrock, but would you use the 750 holley with that or use a Edlebrock carb?
What is your opinion on the edlebrock dominater intake and carb Vs.edlebrock performer rpm
Chillen
I faced the same situation as you. Mine a 95 Ultra 21'SS. Same engine as you have. My boat topped out at 60 mph (summer 110+ degree heat, winter 65 mph) with a Mirage 23P prop. This is based on speedometer readings because I really don't care how precise it is. Bottom line it was a comfortable ride but didn't get me excited.
I chose to go with the Edlebrock Performer heads (oval port) Part number 61459 (new number) These are the Marine heads and are actually cheaper than the street heads. They are hard anodized for marine use and come with 2.25 intake valves and inconnel exhaust valves for marine severe duty. The street heads are equipped with 2.19 intake valves.
The price is less because they do not include springs retainers and locks. You will want to match these items to your cam anyways.
I went with the Performer RPM Air Gap intake and 750 Edlebrock carb. Holley will work fine they just cost a bit more and in my opinion the Edlebrock/Webber will produce more torque. I never heard of an Edlebrock Dominator Intake. Holley does make a Dominator intake or at least used to.
My first cam choice was the Performer RPM cam and was a bad choice as it went flat during the break-in and deposited metal shavings in the engine. First and last time trying their cams. I say stick with Crane, Comp, Isky, Clay Smith or Lunati.
I chose to replace it with a Crane Hyd. roller .598/.610 226/234@ .050 112 lobe center. While I was at it I had a zz502 shortblock so I switched it as well. However you should do ok with the 454.
I replaced the Mercrusier Thunderbolt V ignition with the MSD 6M marine unit box, distributor and rev limiter.
I also added Imco powerflow exhaust and elimanated the bends in my silent choice by removing it and going straight out the transom with "S" bends
I topped the heads off with Cranes gold rockers and a stud girdle for valve train stability.
I tried several props and chose to go with the Bravo1 4 blade 24P prop. It has that set you back in the seat acceleration and stays glued to the water on high speed turns. I did sacrifice about 4 mph over a Mirage 3 blade 25P prop but well worth it on handling and acceleration.
The speedometer now shows well over 75 (only reads to 75) and squirts water all over the place (gotta get that fixed). The ride is exciting, holeshot much improved.
Probably more than you wanted to know. Hope it helps you make the right decisions.
[This message has been edited by Racing Ray (edited March 20, 2002).]
Hey Chillin. To increase you marine engine knowledge I highly recomend the Big Block Performance book by Dennis Moore Merc master mechanic. It is $20 WELL SPENT!!! This book will tell you exactly what you have as far cast pistons, cast crank,valve train etc.
Ray, With cast pistons and crank what do you think is wise HP wise???
I read the Stern adds an additional 10% of stress to your outdrive and transom.
I am going to try the Stern Jack this summer on my 232 with 454 Mag. 385 hp. I would like to know what your boat did stock before the S-Jack. Do you have any clearance problems with the swim platform? Have you checked for stress cracks in the transom??
Check out the Website for the Stern Jack. 77 mph with a 502 could be in your future.
BBCs are known to live a long life producing up to 500 hp on cast components if you don't spin them too high and don't put on the squeeze via blowers or NOS. If thinking of mods from 500 and up I would insist on forged internals.
HI Ray,
Thanks for all the information. My mistake on the carb., your right it is the Holley Dominator I was talking about. I will take your advice Edlebrock/Weber for more torque.
Final question, with all that you've mentioned in your last post can you give me a ballpark $$$$ amount on the cost to do all that you did?
Thanks a million,
Mike
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