working on a 74 25 sport and need some input...
03-06-2011, 12:03 PM
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working on a 74 25 sport and need some input...
i have been working on a 1974 magnum 25 sport and will be putting a sinlge 502 with bravo 3 in in instead of twins. i was looking for a paper template and also information and input on where to mount the drive. we are starting with a fresh blank trason and new stringers and were wondering if we should favor a higher mount or a lower mount. we are not looking for all out go fast because its more of a bar cruiser then go fast now. we will be having a crowd on the boat and need the boat to jump up on plane but also still top out reasonably. and input or experience is welcome. thank you
03-06-2011, 01:40 PM
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I suggest you follow Mercruiser instructions for the X dimension and then a prop professional to hep you decide how far above the factory recommnded x dimension you raise it.
There is also a jig made to align and drill all the mounting holes correctly . . .
Mario L.
There is also a jig made to align and drill all the mounting holes correctly . . .
Mario L.
03-07-2011, 08:20 PM
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Re: your question on the other 25 thread about blowers , I don't have any experience to offer on that , sorry.
I can tell you that I'm running the 2:1 gears and the 'old' 26 inch propset (cupped) . That gives us 4950 WOT when the weather is nice and dry. Now I understand that Merc makes a 'higher performance' B3 propset so you might be able to do better in terms of top speed as well. We can expect high 50's , maybe 60 on a good day.
If you're dissappointed , you can always go back to a B1 anyway. The B3 doesn't seem to be as 'trimmable' at speed as the B1 probably is.
You won't be let down with the overall handling though. The boat eases up on a plane effortlessly and you can pull the throttle way back and still plane. Cornering in either direction is excellent.
I have ours setup where the anti ventilation plate is just about an inch above the keel and there doesn't seem to be any negatives with it there.
If you haven't run yours yet , you're gonna love the ride. It's a real wave crusher even in nasty stuff . That's where the extra 'Magnum hefty weight' pays off.
Remember , if yours started out it's life as a twin engine installation it'll have hooks on the chine , the single engine ones didn't.
I can tell you that I'm running the 2:1 gears and the 'old' 26 inch propset (cupped) . That gives us 4950 WOT when the weather is nice and dry. Now I understand that Merc makes a 'higher performance' B3 propset so you might be able to do better in terms of top speed as well. We can expect high 50's , maybe 60 on a good day.
If you're dissappointed , you can always go back to a B1 anyway. The B3 doesn't seem to be as 'trimmable' at speed as the B1 probably is.
You won't be let down with the overall handling though. The boat eases up on a plane effortlessly and you can pull the throttle way back and still plane. Cornering in either direction is excellent.
I have ours setup where the anti ventilation plate is just about an inch above the keel and there doesn't seem to be any negatives with it there.
If you haven't run yours yet , you're gonna love the ride. It's a real wave crusher even in nasty stuff . That's where the extra 'Magnum hefty weight' pays off.
Remember , if yours started out it's life as a twin engine installation it'll have hooks on the chine , the single engine ones didn't.
Last edited by madbouyz; 03-07-2011 at 08:22 PM.
