What RPM at WOT should a 1990 Tristar 220 with a Indmar 390 HP 454 7.4L be at?

[Arisenagain]

I'm trying to figure what the RPM should be for this engine at full throttle. Right now it runs at 4200 RPM with what I believe is the stock FEDERAL 14 X 13 X 1 LH cupped prop. The transmission is 1:1 ratio.

I've read up to 4800 RPM so I'm trying figure if it is just the prop or the engine needs some tuning.

Anyone have any experience with this configuration?

[snork]

That thing should be run'n at least 4800 rpm with that prop

[j.mccreight@hotmail.com]

Per the owners manual, max 5000 rpm, stock prop is 13x13.

[Arisenagain]

Thanks guys...I thought it was off a bit. I believe it is the prop. The boat has only 280 hours on it and the engine is running smooth from what I can tell so far.

I called ACME and discussed props as I wanted a new one and the recommended model 431 which is a 13 X 13 X 1 unit that has more surface area then the Federal unit I have now. Jim (sale rep) from ACME said it should bring my rpms up to 4400 to 4600. He also hinted at model 475 which is a 13 X 12&5/8 X 1.

So I ordered 431 with a 30 day exchange if it does not work out.

If it is not the prop what else would prevent that motor from getting up to 4800~5000 rpm?

[TRBenj]

What makes you think you have the 390hp version of the 454? That was the HO, and pretty darn rare. The run-of-the-mill 330hp version was much more common.

Barefoot Nautiques with the regular 330hp version pull both their stock 14x14 Federals and the replacement 13x14 Acme (#1598) in the 4400-4600 range. I havent tried one, but the RH version of the 13x13 Acme (#430) would probably turn in the 4600-4800 range. Ive seen the 13x12 (#540) turn a tick over 5,000 (but boy, what a holeshot).

By the performance youre getting, I suspect that you only have the 330hp version, which will perform best when propped to run 4400-4600 (unlike the better breathing HO version). So the 431 will likely be a good choice. To spin higher than that will likely start to give you a slightly diminished top end speed (but give you a better holeshot).

[Arisenagain]

What makes you think you have the 390hp version of the 454? That was the HO, and pretty darn rare. The run-of-the-mill 330hp version was much more common.

I have all the original manuals for the boat and engine. The original owner stated that there were only eight 1990 Tristar 220's made with this option from factory. The Mastercraft Tristar owners manual specifications for the Chevy 454 option shows two models offered at the time of purchase:

Model 350 @ 390 HP and Model 400 @ 425 HP See the scan from the manual below.

The original owner highlighted Model 350 which is the 390 HP 454 as the option he had purchased with the boat.

Now unless the manuals are misprinted or they exaggerated the HP ratings that is what I am using as my point of reference.


As for the props suggestions I will have to report back on what the ACME 431 13X13 does to RPM and other related characteristics.

[LYNRDSKYNRD]

You know we need pics to confirm that you even have a boat

Love to see some pics in other words.

[Arisenagain]

Originally Posted by LYNRDSKYNRD

You know we need pics to confirm that you even have a boat

Love to see some pics in other words.

Since you asked see them in this thread posted here:

http://www.mastercraft.com/teamtalk/...6&postcount=51

[TRBenj]

I didnt notice that youve got a Tristar 220. That may make a small difference, as the 190 I was envisioning would have been a more apples to apples comparison with the 19' Barefoot Nautique in size and weight.

The 5,000rpm recommended operating range would be consistent with a HO 454. To my knowledge, both HO and non-HO versions were propped the same (~14x14 on the 19' boats with 1:1 trannies)... the HO's simply had the extra hp to bull the prop more RPM.

At 4200 with a 14x13 though, you are nowhere near HO levels of performance, Im afraid. Any chance the longblock was replaced with a lower hp version? How much do you trust the tach? Have you checked to see what your top speed is (with a GPS)?

If that 4200 is to be believed, then I think the boat will run significantly better with the 431, regardless of which version 454 you really have.

[LYNRDSKYNRD]

Originally Posted by Arisenagain

Since you asked see them in this thread posted here:

http://www.mastercraft.com/teamtalk/...6&postcount=51

Ah thanks love the lines of that boat.