Is it time for a Re-power? - 454 (310hp) to 502 (415hp)

[nova_gts]

I currently have a 98 Sea Ray Sundancer 290 (10,000 lbs) with a single 454 carb (310 hp model) and a Bravo 3 with a 20p prop. The boat is sluggish to say the least - it hates even having a full tank of gas and is only getting worse with age.
I plane at about 3,700 rpms (85% throttle) and it really likes to run closer to 3,900 at 25mph

I've found a decent deal on a newer 502 mag (415 hp) from 99 (gen 6) and was trying to some opinions on whether the upgrade was worth it... will it have adequate power, can I go up a prop size and increase efficiency/cruising speed? I believe the only modification I will need to make to the boat is adding a new fuel pump correct?

All opinions are welcomed - The reason I'm not really looking for a new boat is I've gotten this one almost perfect in almost every aspect except power (and its paid off).

Thanks!

 

[Mischief Managed]

I would do that in a heart beat. The new engine should have its own fuel pump.You may not need to re-gear or re-prop. I think the 502 MAG has a higher WOT RPM than the 454. That said, you still may need to have the props cupped or something to get it spot on. What's your WOT RPM now?

 

[nova_gts]

I rarely push it to WOT but it is probably around 4400 rpms

 

[Eric 3.7LX Alpha 1]

Looks like those Sundancer 290's also came with twins....

 

[nova_gts]

They did, I don't think they make a boat this big with Singles any longer, but adding a second motor isn't an option.

 

[alldodge]

Did the same thing your contemplating several years ago and liked the way it turned out. Pulled the 454 and installed a 502 MPI in my 10K Formula. If you have a 2.0 ratio drive your good. Will go from a 20 pitch to probably 24 pitch and WOT on the 502 is 5200 rpm. Need to change from an exhaust boot in the drive to an exhaust tube. I added silent choice and thru hull to help it breath better.

Just this year I pulled everything back out and had the 50 brought up to 545hp. Now running 26 pitch props

 

[nova_gts]

I think I have a 2.2 gear ratio

 

[alldodge]

I think I have a 2.2 gear ratio

Shouldn't be an issue, just may need to go up to 26 pitch, don't know. The Searay 29 weights in about the same as the Formula 27, shes is a bit wider then mine also

 

[Tail_Gunner]

keep in mind a old 454 330 hp can stand the test of time quite well and 502 well there a bit different animal have the engine checked out thourghly...502's are meant to be used the very name begs performance...aka run hard and put to bed wet...pun inteneded.

 

[Mischief Managed]

The 454 you have is rated at 330 crankshaft HP (300 at the prop shaft) and the 502 is rated for 415 at the prop shaft. You will be looking at 115 more HP at the prop. If you are seeing 4400 RPM with the 454 and it's really making 300 HP, you will be propped to hit 5175 RPM with the 502. I'd try to get it to 5000. If you have 20" props, 20.7" would get you to 5000 RPM, and that could be accomplished with having your 20" props cupped. If you want a lower cruising RPM, the 502 can safely be set up to run at 4600 at WOT, which you could see with 22.5" of pitch. 22" props would probably be a great compromise with a 4700 WOT RPM.

 

[jfried]

I currently have a 98 Sea Ray Sundancer 290 (10,000 lbs) with a single 454 carb (310 hp model) and a Bravo 3 with a 20p prop. The boat is sluggish to say the least - it hates even having a full tank of gas and is only getting worse with age.
I plane at about 3,700 rpms (85% throttle) and it really likes to run closer to 3,900 at 25mph

I've found a decent deal on a newer 502 mag (415 hp) from 99 (gen 6) and was trying to some opinions on whether the upgrade was worth it... will it have adequate power, can I go up a prop size and increase efficiency/cruising speed? I believe the only modification I will need to make to the boat is adding a new fuel pump correct?

All opinions are welcomed - The reason I'm not really looking for a new boat is I've gotten this one almost perfect in almost every aspect except power (and its paid off).

Thanks!

If the deal on the 502 is good, and the engine is thoroughly checked out, this seems like a no-brainer. The next logical step up would be a 496, and those tend to be not cheap.

 

[Mischief Managed]

I was under the impression the old 7.4 was 330 HP model, but I re-read the original post and realized both engines are rated at the prop shaft. I still think 22" props would work really well.