Max RPM

[supramariah#1]

Does anyone know the Max RPM of my boat?

Oh and its a 1988 Supra Mariah. 351W. No mods.

I would like to see how close I am to it at WOT. Trying to see if I am gonna get a new prop.

[csuggs]

WOT on a 80's model 351W should be about 4400. My 86 Sunsport with the same motor will only get about 4100 with the standard 13x13 prop - pretty sure she runs out of hp before getting to WOT of 4400. I'm going to try a 13x11.5 and see I pick up a few hundred rpm.

[beast 496]

4200 to 4600 on the ol 351 Fords.

[csuggs]

My '83 351 PCM hits 4500 easily with 20 year old 13 x 13 LH prop.

At 4500rpm what's your indicated speed?

[csuggs]

With GPS, I'm right at 39-40 mph. Used it to dial in the NOS Airguides I just put in.

Good answer, that's what I hoped you would say. Is your transmission 1:1 ratio? If your turning a 13x13 with 1:1 trans your mph should be real close to your speed (i.e. 2000rpm = roughly 20mph and 3500rp = roughly 35mph, of course this can vary with how the boat is loaded/weighted). This rule of thumb has held true for my Sunsport and my friend's Comp with the same driveline - 351W, no modifications, 13x13 prop and 1:1 transmission. I wonder if your 20 year-old prop is worn in a way that makes it spin easier without as much "bite". That would explain the higher rpm and slower speed, unless of course you have a reduction transmission.

[csuggs]

Daniel - I wonder if it has always run up to 4500. You have the same sticker that mine has (or had on the OEM valve cover)

[cadunkle]

It shouldn't hurt a 351w to spin higher than 4400. I've never heard of 351w rods that couldn't take such a low RPM.

Now, interesting question... When did Supra put 460s in these boats? If my 454 ever blows up I'd enjoy building a 545 stroker for it. I guess all that would be necessary is a bellhousing, coupler, and mounts... Mounts being the tricky part I guess.

[csuggs]

It shouldn't hurt a 351w to spin higher than 4400. I've never heard of 351w rods that couldn't take such a low RPM.

Now, interesting question... When did Supra put 460s in these boats? If my 454 ever blows up I'd enjoy building a 545 stroker for it. I guess all that would be necessary is a bellhousing, coupler, and mounts... Mounts being the tricky part I guess.

I think the decal you're reading that refers to the 460 is actually a PCM decal, not a Supra decal. I'd bet PCM built 460's for some kind of commercial utility boats like inboard fishing or crabbing boats? But not for Supra.

[sybrmike]

I've heard of 440's in early Supra's, but never a BBF. I ran a 460 in an old jet - pretty common & lots of marine parts available. You could probably make something work if you really wanted to...

[supramariah#1]

This should answer a lot of questions I frequently see on here about servicing.
Original sticker. Original engine...no mods......1:1 tranny.
Mine goes above max engine speed at 4500 rpm.

Holy moly. I saved that photo. its got a wealth of info all in one easy place. thanks!