motor change - what works?
 

The 1990 21' Citation I have has a 4.3 mated to an alpha 1 drive. The 30 MPH top speed is killing me. I had been thinking for swapping it with a 5.7 lt v8.

I've been told the alpha 1 is good as loond as you dont put serious HP to it.

If I can get to 50 mph (a 20 mph gain) I would be happy, Is this possible?

All help and comments are appreciated..

Mike

The 4.3 should push it faster than 30. you need to find the problem with the current setup first. what rpm? ratio pitch and type of prop? The alpha should stand up to a 5.7 but you should change to a 1.5:1 gear ratio for a V8.

Its spinning a 19 alum. Michigan wheel. Not sure on gear ratio. How can I find out? The rpm are 4900 at WOT. The prop needs to be replaced as it has been beached a few times. I have a new one that should be here this afternoon. I know that mat be some of the problem but only a few MPH differance if that. How many rpm should it be turning?

Thanks


Mike

if yoru interested i am goign to have a 5.7vortec out of a truck in a week or so. It blew ahead gasket but taht is pretty easy to change I foudna new engein (from a wreck with 30k miles on it) for like $1500 I figure dit was easier to change the entire engein and rebiuld the other one at my leisure later this summer. I need my truck runngin now!!!! If your interested in it e-mail me. [email protected] i'd let it go pretty cheap

puder

you have mail

That is a 1.84 gear ratio.

The 5.7 uses the same mounts as the 4.3 V6....I have thought this over time and time again...

Tommy

Downside?
 

Tommy it sounds like there may be a downside to this that your holding back. If I'm making a mistake please let me know. I have also looked into getting a setback bracket and pulling the I/O & going for an OB.

I know I'd have to reglass the transom etc. But I've done that before. I just figured swaping to a v8 would be less expensive & better overall.

Mike

A 19" pitch prop should put you close to 40mph at 4900rpm's with that ratio. are you using GPS for speed? Verify the gages both tach and speedo for accuracy so you have good data to start from. I have 2 friends with 4.3's in about the same size boats 19' and 21' and they both run over 40 the 21 chris craft is close to 48 on gps on a good day. good luck

IRONMAN - I'm just using the factory speedo. Well I guess I need to GPS it & see exactly what its doing. I got a new prop so we'll see.

I was thinking of adding a drive shower. Would it help or just be wasted money?

Mike

Wasted money in my opinion. If you had serious horsepower running some serious rpm it might be worth it. I think you could spend your money on more important items.