top speed for a 1976 20' spectra

[andrewszalontai]

Hey everyone... I have finally had to retire my 429 engine in my 1976 20' Spectra after 20 years. I am very happy with a jet drive, but need more speed. I am wanting to get 85 MPH out of my boat and need to know from all of you Spectra fans if this is possible.

It will have to be on pump gas, I would prefer to stick with a Ford big block. Everything on this engine now is basically just over stock. So a full fresh build is what I am aiming for. What are the pros and cons of N/A or blown... I am mostly in fresh water.

I run a modified JE Berkley pump with a place diverter on a AA impeller. What kind of HP and Torque will I need to accomplish this 85 MPH? Will the boat handle it?

All help is appreciated.

Andrew

[SofaKingFast]

I had a 1976 spectra 18' mini day cruiser with a 460 it did 58mph.it had an E pump berk. I'm not sure if that big boat will run 85 on pump gas. You need full stringers, and A LOT of hp. I would guess 1000hp, but then you need a new pump. I think 65-70 would be a more obtainable goal. Not to mention all the bottom work that would need to take place. Just my opinion.

[Ol Blue]

You can build a lot of HP with a 429/460 with a stroker kit and some alum heads like Trick Flow. Upgrading your exhaust will need to be done to match the exaust flow. Check out 460ford.com for different builds.

Now the question, is this a full stringer boat? Not sure if you want to run it up to 85 in the chop without.

[Yellowboat]

talk to lakes only. he owns high flow dynamics. all they do is 385 series motors.

[FASTJTBT144]

As we all know spectra is known for building great strong boats in fact this makes them heavy for these times not saying the 85mph cant be reached but with a pump it will take alot of work. Alot of bottom work for sure around 1000hp or so well built pump and set up.Dannys dcms are the same bottom and built by todays standers with different glass/ resins
that are stronger and lighter then the past hes had a few that seem to run very well with a pump.

[Flat Broke]

85mph with a jet and a stock Spectra bottom will take 850hp all in by 5800-6000 to be able to use an impeller that will allow the boat to plane out alright. You can get that kind of HP out of a BBF, and I'd second the recommendation for talking to Paul at High Flow Dynamics if you want to pay someone to do it.

Be prepared to spend a couple grand in the pump (new shaft, stainless impeller, better loader, shoe/rideplate, and inducer) otherwise all the HP in the world isn't going to matter.

I've litterally been there/done that, and can tell you I would strongly consider other propulsion systems or hull designs. Nothing against the Spectra, just that what makes it stable and well loved hurts it in the quest for speed. You might try talking to Jeff Bennett and seeing what he thinks could be done to the bottom of a 20 to increase efficiency so whatever HP you build will go further.

If you really just want to go 85 in a family Jet, there are more efficient ways to get there when it's all said and done.

Chris

[Ol Blue]

LakesOnley web is highflowdynamics.com