Big Ass Tahiti

[shirkey4750]

Bring it to Lake James.

[Squirtcha?]

We have a few other questions about this 21' Tahiti. How heavy do you think that hull is and if he puts a 555 ci 875 hp motor in it what impeller do you think he will want to go with. Bronze or stainless and A or AA cut. The 555 is a fresh built motor that was just put in his outlaw street class drag car. Do you think it will live in the jet boat and what will be the MUST DO changes he need to know about. Just the cam or are there other things that need changed. Last question is about the logs. Will they flow enough for that kind of power plant or will they be a problem. Thank you!
Fred
.
No expert, but you're not getting a lot of responses from others. Hell..........I'll throw down.
I would say start out with the AA and see where it puts you RPM vs speed-wise. Bigger, heavier boats usually respond better to the bigger impellers, but a lot will depend on where that motor is making it's hp numbers at. If the mill is making it's peak hp at 6000+ rpm you'd probably want to think about re-camming it. Although a smaller impeller might get it into the proper rpm range, it would probably result in a lot of slip when trying to get the boat up on plane.
I would think that since the motor is from a drag car the rpm range will be higher than what you would want in that boat. I would think shooting for max hp number around 5400-5500 rpm would be about right.
The beauty of going with the bigger impeller is you can always cut it down as opposed to starting too small. You can't add to it.
Can only guess about the logs. From what I've seen, these things most always respond favorably to a better flowing exhaust. I'd think that the logs would be a major hinderance on that particular motor.
Might consider going to an Imco style exhaust, or Lightning jacketed header rather than water injected headers and he could stick with the enclosed engine compartment.
Just opinions.

[CVX20]

Bring it to Lake James.
Lake James with this boat!!
Hell we had reservations about hauling it 20 miles across town when we picked it up because the trailer is so rough but we do have a few SML rat rods that are giong to make the trip for the first time.

[CVX20]

Thanks Squirtcha
That's just the kind of information that he is looking for. So if the cam change is going to be a must then the next question has got to be about lift duration and lobe seporation and yes I can clearly see how it would be better to mill some off vs trying and put some back on so he needs to look for look for an AA impeller. Does it need to be made out of bronze or stainless steel. Thanks for the help!

[Squirtcha?]

Thanks Squirtcha
That's just the kind of information that he is looking for. So if the cam change is going to be a must then the next question has got to be about lift duration and lobe seporation and yes I can clearly see how it would be better to mill some off vs trying and put some back on so he needs to look for look for an AA impeller. Does it need to be made out of bronze or stainless steel. Thanks for the help!
Cam spec questions would have to go to someone who knew their stuff motor-wise (not me). I've seen some nice motors that have hit their mark for hp/rpm come from Chris Straub's cam recommendations here on the boards. I'm going to shoot him my motor specifics when it comes time to build again. Sounds like he's a good goto guy and a straight shooter from all I've read.
Reckon you could run the engine specifics by any of the cam companies and get some kind of idea too.
As for the impeller, I would think he should probably go with bronze or stainless if he's going to be around that 800+ hp number. Either would work fine I believe. I'm running 650 hp and still using an aluminum, but that's really pushing it.