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bigd1
09-12-2004, 04:11 PM
Hi,
Let me start by saying that I'm no gear head. I don't know how to build motors or anything like that. My first boat (3 yrs ago) was a Tige' 22i inboard which I still have (for sale by the way). Once I spent some significant time on the water I knew that I had the "need for speed" and the inboard was just not the ticket. Driving down the street one day I spotted a Magnum 27 Sport with a single BB Chevy 454, Borg-Warner transmission, and Stern Power outdrive for cheap. I bought it and have used the boat as-is this summer (even thought the weather around here has sucked) - haven't touched the Tige' since. I know nothing about the motor or drive train other than it runs (no hours, etc). The guy I bought it from has apparently moved, so he is no help either.
I guess my issues are:
Speed: I'm maxing at 50-55 MPH or so with a max of 4000 RPM.
Power: I think I need more power to get more speed, but also know I need more RPMs.
Prop: I don't know squat about all the ins and outs of props.
Tranny: My inboard has a Borg-Warner, but I've been told Mercury outdrives don't. I'm confused, help me out here. I've got to believe the weight of the tranny is an issue.
Drive: Stern Power went out of business a few years ago, but seems to be operating again. My problem is that there is nobody in my area who has ever seen one. Plus, I would like to add hydraulic steering (my current steering sucks).
My first questions are:
Should I just look to upgrade my current engine (e.g. rebuild and selected upgrades) or go to a larger motor like a 502?
What drive?
What steering?
What Prop?
All I know is that I want to go a LOT faster, but want to do it in this boat (at least for next summer).
Some thing I DO know:
Most of these boats are rigged with twin small block 350s (it's not a big boat).
I've seen some race-rigged versions of my boat advertised as doing 90+ MPH.
I'd be happy with 70+ MPH.
I do get some prop torque when trimmed down, decreases when trimmed up.
Thanks.

RebarBox
09-16-2004, 04:52 AM
bigd1,
I can tell you what I know, which ain't a lot. :D
Your Magnum is probably around 5000 to 6000 ibs, guessing? The old magnums are heavy. Thats alot of weight for a single engine. More HP will get your more speed with the right prop configuration but if you are only turning your current prop at 4000, I would try re-proping to get in to the 4800 to 5000 range and see what the speed does. If your wanting to see 70ish, and my guess on your weight in close - your probably going to need to look into more HP.
What Stern Powr are you running? 101, 103, 105 or MX-07? Your can get internal hydro steering on the stern powrs, if you can find the parts.
I can tell you my old Cigarette 28 with twins, producing alittle over 800 HP total and running the Borg Warner trans and Stern Powr MX-07 drives has NOT ever seen 70!
69 mph - GPS is the best I can do at 5200 RPM.
Good Luck

bigd1
09-19-2004, 09:04 AM
Thanks for the Help Rebar,
Our SWAG estimates put the weight of the boat in the 5000 lb range (dry). Not massive, but big. My mind is made up to get more HP over the winter, just have to see what my options are.
I've been told the drive is a model 107. Attached is a really bad pic but you can kind of see the drive. I talked with Dennis Andrews at American Propulsion Systems which is who now makes Stern Power, and he told me parts are available for this drive, but they are discontinuing it at the end of the year. It's pretty odd, he told me they are in business, making outdrives, but not selling to the public, and was pretty tight with the info. Not sure what the deal is there, they must be living off of a Navy contract or something. I've got no complaints about the drive itself other than it's old, rare, and parts are scarce, and if I'm gonna pry open the wallet for power, I figure since it's open....

ECeptor
10-17-2004, 05:39 PM
What ratio is your drive? If you don't know, then find out what pitch your prop is. Post here and I'll back calculate your drive ratio. From there I can recommend a new prop pitch that will get your revs up. I can also recommend a prop shop if needed.
Nice looking boat!

bigd1
10-23-2004, 04:34 AM
Thanks ECeptor. I'll do it. I', slowly moving forward on this project - totally buried with work (but that beats the alternative). I did pick un new power - 632 ci BBC, ~ 900HP. This should help!

missboatnam1
10-27-2004, 03:53 PM
i thought you were talkin car magnum :rollside: well, im here if you need one of them!! :smile: