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


Arisenagain
06-14-2012, 05:25 PM
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
06-14-2012, 06:54 PM
That thing should be run'n at least 4800 rpm with that prop

j.mccreight@hotmail.com
06-14-2012, 09:55 PM
Per the owners manual, max 5000 rpm, stock prop is 13x13.

Arisenagain
06-14-2012, 10:43 PM
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
06-18-2012, 01:53 PM
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
06-18-2012, 04:46 PM
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
06-18-2012, 04:52 PM
You know we need pics to confirm that you even have a boat:D

Love to see some pics in other words.

Arisenagain
06-18-2012, 04:59 PM
You know we need pics to confirm that you even have a boat:D

Love to see some pics in other words.

Since you asked see them in this thread posted here:

http://www.mastercraft.com/teamtalk/showpost.php?p=847256&postcount=51

TRBenj
06-18-2012, 06:01 PM
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
06-18-2012, 06:08 PM
Since you asked see them in this thread posted here:

http://www.mastercraft.com/teamtalk/showpost.php?p=847256&postcount=51

Ah thanks love the lines of that boat.

jeff shelton
06-18-2012, 09:28 PM
I was doubted just like you about my boat having this very rare HO version of the 454. I contacted indmar at gearhead@indmar.com by request of a certain individual and got a response from Larry Engelbert. He confirmed that my boat was equiped with the HO version. According to him the HP rating for the HO version is 400. He also sent me the specs and a tune up chart and I've attached them for reference.
My boat has the powerslot trans and with acme 14x20 it turns around 4600 rpms.

Here is the link to my discussion
http://www.mastercraft.com/teamtalk/archive/index.php/t-44530.html

Arisenagain
06-19-2012, 12:26 AM
I was doubted just like you about my boat having this very rare HO version of the 454. I contacted indmar at gearhead@indmar.com by request of a certain individual and got a response from Larry Engelbert. He confirmed that my boat was equiped with the HO version. According to him the HP rating for the HO version is 400. He also sent me the specs and a tune up chart and I've attached them for reference.
My boat has the powerslot trans and with acme 14x20 it turns around 4600 rpms.

Here is the link to my discussion
http://www.mastercraft.com/teamtalk/archive/index.php/t-44530.html

Excellent. I'll have to figure out which 454 I have exactly in my boat that is listed on that PDF file so I can get it tuned correctly if needed.

I just have not had time to get into the details yet but I will soon since it seems the RPMs should be closer to 5000. We will see what the new prop does for the RPMs and what GPS speed I get.

TRBenj
06-19-2012, 11:32 AM
Jeff, Id still like to know the casting numbers off your head or intake as I asked in that previous post. Based on your boat's as well as Arisenagain's performance, the engine that Indmar was calling 390hp sure seems to perform consistently with what PCM and every other manufacturer were calling 330hp.

At 4600RPM it ran 50mph on GPS.

^^Those numbers are right on the money with my uncle's stock '86 Barefoot Nautique with the 330hp PCM 454.

The guys I know who have some experience with the PCM HO 454's (dealer installed) said they turned the Ski Nautique 2001 into a legit 55mph boat. Ive never been in one or even seen one with my own eyes (they are super rare), but that hull is good for about 45mph with the 351w and 49-50mph with the 330hp. When our Barefoot Nautique had a HO longblock in it (installed by a previous owner), it was good for 55-56mph on the GPS once we got it tuned up.

A true HO 454 will have rectangle port heads (not oval port) which can be identified by the casting number on the heads or intake. My guess is that Indmar may have been calling some of their oval port engines "HO" and overstating the horsepower. Personally, I've read that the 330hp claim out of the regular 454 that PCM/OMC/Mercruiser put out was overstated by a good amount... and I believe it! They perform like they have about 300hp, IMHO.

jeff shelton
06-19-2012, 01:30 PM
I did post the # of the intake manifold in the previous thread it was 6269318. While I'm no engine expert I have to believe that indmar wouldn't give me information that is incorrect. I do understand that it could have been considered an HO with out having the actual heads or manifold. Again I just have to hope the information provided by indmar is correct.
However the way you questioned me and others at times is inappropriate. Comments like, what makes you think you have an HO or I'm not entirally convinced you have an HO version. You could just ask for the part #'s in a more constructive way to help members accurately identify the parts.
While you and others on this forum can offer tons of knowledge to others. At times it is the manner at which you respond that is off.
With that be said and based of the #'s from my intake I hope that you could help me accurately identify which version of the 454 I have. I'm out of town working and want be back home until the 4th of July. So if there is any other info needed I can get that information then. I will also get a more accurate reading on rpm and speed then. I will also put my other prop on to see the difference

johnlanguab
06-19-2012, 01:35 PM
I wonder why the manual states to use only SAE30 oil...

TRBenj
06-19-2012, 04:21 PM
Not questioning your integrity, Jeff- just curious if what Indmar called an HO was consistent with what GM, PCM, Mercruiser and everyone else called it. I try to base my posts on facts and logical reasoning, if it came across as insensitive, that was not the intent.

I just did a search on that casting number and it appears to be a legit rectangle port intake... so Im sure the heads match. That makes it a legit HO motor, so at least Indmar's terminology was consistent with everyone else's.

It would concern me a little that the 2 boats in question are running relatively low RPM's and speed. The prop sizes look to be in the ballpark for the engine/transmission combos. I might start with a compression test and move on from there- I would expect an HO big block with nearly 400hp to be running at least 4800-5000 (5200 would not surprise me in the least) and be flirting with the mid 50's on a light Prostar hull. The Tristar 220 might be a few ticks slower.

bcrouch
06-27-2012, 08:03 PM
I just purchased the Acme 431 3-Blade prop from Nettles Props down in Texas...I called the Acme Manufacture direct in Michigan and discusssed all the 3-Blabde versus 4-Blade issues.....I had a 4-Blade Mercury prop on the boat when I purchased the boat from Texas Mastercraft four years ago...WOT speed was 48 mph at 4800 RPM's and that was with GPS on glassy H20 conditions...that being said...the final verdict shall be determined tomorrow on the H20...I went with the 3-Blade Acme# 431...let you know how things go...I was told the holeshot will be great and I will lose a little top end...last time I checked 36 mph was all the speed I needed to barefoot...so if I lose a little speed no big deal.....

Brian
Butler, Pennsylvania
East Brady, Pennsylvania
Allegheny River

Go Steelers!!!