Repower 1980 Tri Cabin

[Tri-Guy]

Hi again, purchased a pair of Crusader 5.7 MPI Captains Choice. I will be removing a great pair of 360 Chryslers, they run great but time to go newer. I'll take a bunch of pictures as the project moves along and post up. How much more efficient do you think they will be? 275 hp Chrysler to 330 Crusader will I feel that extra power? I know it's not a ski boat just wondering about the extra power and how much better on gas. Thanks J

[jimbo36]

5.7's 330 H.P. ? I thought 260 H.P. and 330 H.P. for 7.4's?? Have things changed that much??

[Tri-Guy]

Yes Sir, things have changed over the last bunch of years. 5.7 carbureted Crusader is 300 hp and 5.7 Multi port fuel injection is 330 hp. The 7.4 454ci is no longer made new and the 8.1 496 ci is gone. You can still get them but it's reman only. I'm excited about the MPI 330 hp just not sure how much torque they put out. We did the same project on my Brothers 32 caver sport fish. We went form 1984 270 hp crusaders to the 330 hp. In his boat it made it feel like a new boat, I'm wondering how it will do in my much larger boat. How is the torque of the crusaders compared to the 275 hp old Chryslers ? I have been told by a few people the torque on the 360 Chryslers is good for moving a big boat. I will see how the MPI Crusaders do next spring. The boat runs good as is now, hanging on the anchor as I typing now.

[jimbo36]

Very cool! I guess I should not be too surprised. My Cadillac CTS V6 pumps out 306 H.P. All the best with your project. jimbo36'

[prowlersfish]

It should be faster , but you may have to go down in pitch slightly as the make its HP at a much higher rpm ( 1000 rpm more ). your cruse rpm will be higher too . with you should get much better fuel burn Due to the EFI . I would start with the same props and go from there .Assuming your not changing the ratio .

[captainmaniac]

Not positive, but switching from Chrysler to GM blocks you may also have to rework some of your instrument panel. If memory serves me correctly, current or resistance expected from sending units on Chrysler vs GM blocks is sometimes different depending on the instrument, and the gauge has to match the sender.

[Tri-Guy]

Thanks for the replys, staying with the same gear ratio. Prowler your thoughts are the same as mine, try the old props and repitch as needed. I really hope they FEEL much stronger, but done expect much on the top end more for cruising speed. I already bought new Faria Chesapeake gauges to replace everything while repowering. Thanks again, and keep any ideas coming at me during the project. Doing this project because after 10 years I still love the boat and it's cheaper than starting again on another boat. Prowler, do you think I can get near 1.0 miles per gallon at cruise with this set up?

[prowlersfish]

Your fuel burn will depend on how you run it and how much weight you carry . Some of the mileage clams I have heard I find hard to believe . I would guess a 20-30% improvement but that's only a guess . Your mopars could be tuned in perfectly to get great mileage so the improvement would very little . But your could also be gas pigs ( even in good tune) and you would get a BIG gain .


A lot of factors at play could you get near 1 mpg ? maybe , onced you find the sweet spot of the boat/engine combo . I am running diesels on my F36 (conv) and I am just getting over 1 NMPG at speed .( I run with a lot of gear) I have made trips and gotten over 2.5 but that included a lot of hull speed running .

Bottom line is you should see a improvement and I believe you will be happy .

Whats your mpg now ?