Proper WOT on upgraded 5.7L vortec engine.

[tmh]

As I've discussed here a few times, I just re-powered my boat with a 1987-1992 vintage Mercruiser 350 Mag 5.7L engine. The engine cover says 4200-4600 WOT rpm range. However, this engine has been upgraded to a Vortec (8 bolt configuration - was told it had to be an upgrade as the Vortec intake was not available when this engine was made.)

Does this change the WOT Max rpm recommendation for my engine? I have seen some torque graphs that show the newer 5.7L Vortec seems to hit max torque closer to 4900 rpm or so. Is it a problem to run this engine to that high of rpm on occasion?

We only run at max WOT for short periods once in a while but I'd like to know what I'm shooting for when I test some props soon.

Thx.

Thanks.

 

[walleyehed]

Re: Proper WOT on upgraded 5.7L vortec engine.

4900 won't bother it at all...
Question...what engine did you have installed before?

 

[tmh]

Re: Proper WOT on upgraded 5.7L vortec engine.

I had a 1985 305 5.0L with 2 bbl carb. It only pushed my 17" SS prop around 4200 rpm max WOT. I think it may have been a tad short of the 200 hp it had when new.

Had the boat out for a bit yesterday with the new 5.7L engine. Only tested briefly - had a 19" SS prop going at around 4900 rpm per my tach and 48 mph on the speedo (I forgot my gps, the speedo tracked 1 mph over the gps last year). i'm going to run these #'s thru a prop calc to see if it's reasonable rpm and speed.

looks like I'll have to make a decision on whether to try a 20" 4-blade or 21" 3-blade or stick with the 19" which looks to be a bit underpropped but should be good for water sports I'd assume. maybe the 20" 4 blade would be also and get me down a bit on rpm. I'm not doing anything until I test it a bit more and use the gps.

 

[wca_tim]

Re: Proper WOT on upgraded 5.7L vortec engine.

Sounds like you may have been overpropped before and are now just about right.

 

[walleyehed]

Re: Proper WOT on upgraded 5.7L vortec engine.

If you DO try a 4-bld, the Stiletto BayPro series has shown excellent results on Deep-V I/O's. The BayPro is known to have real good over-all lift on this style of boat and if it decreases the wetted surface, scrubbing drag like I think it will, you may need a 22P BP series.

 

[Tail_Gunner]

Re: Proper WOT on upgraded 5.7L vortec engine.

Agreeing with WH here. i have a 20 on a 19' boat @2800 lbs 20 degree dead rise..Lots of midrange punch, very low planeing speed's, the prop will actually do 3400 rpm @32 mph and 54.8 mph at 4900......So far i have not found a prop that has as much grip and speed as the BayPro 11 series.....But im am going to try a merc 21p 4 blade soon...just for ummm because..

RC contruction has a 22 on the same boat with a 22 and a 5.7 it can turn the 22 to 4200 with a dead hole.......

 

[tmh]

Re: Proper WOT on upgraded 5.7L vortec engine.

Thanks for the info guys. I may try to get me one of those BayPro props. Is the "Series 11" a special type? Do they make both 3 and 4 blade props for my application? Seems if the 4-blade picks the boat up a bit it may be better on both low and high end for my boat.

Even if it is slightly slower than a 3-blade, my boat does need to gets it's heavy arse up a bit, I know that. I'd expect it may really be a nice prop for me. I'll do some more tests on the current 19" prop then maybe go 20" or 22" as was recommended.

EDIT: OK, looked around on eBay, other online stores and I see a Bay pro 1, 2, and 3. looks like the BP1 is for smaller engines. The BP2 is for 135hp up and boats 16' and larger, the BP3 is for 135hp an up and boats 20' and larger. Now, mine is below 20' (19') but outweighs many 20' and even 21' boats. So which is a safer bet for me the "2" or the "3"? They both look to be 14 1/4 Dia. The "2" comes in even pitch #'s, the "3" odd. Hmmm......any other difference? Maybe the BP3 21" would be a good one for my rig?

 

[walleyehed]

Re: Proper WOT on upgraded 5.7L vortec engine.

The BayPro II is the one you want....the III is for adverse/offshore conditions and has a different blade design as does the BP IV which is for bassboat apps.
Not sure where you got the app info, but the BP II is for 150-up outboards and sterndrives.
We sell the complete Stiletto line right here at iboats as well.

 

[tmh]

Re: Proper WOT on upgraded 5.7L vortec engine.

OK, thanks again, WH. Looks like the BP2 for me! I searched it here and read lots of threads saying the BPII performs great in low-mid range speeds, great handling, and pretty good top end as well. Many report much improved cruising efficiency. I'll use THAT when explaining to my wife my reason for buying yet ANOTHER prop! I'll figure out 20" vs. 22" once I get all my current prop performance info.

I looked on iBoats under props and it brings up the prop selection window. So, i put in my Mercruiser Alpha One 5.7 L 350 Mag engine and it does not show the Bay Pro props for a 20" pitch. Nor does a search for "Bay Pro" under product search find anything. How else can i find them here? The best price I see is $319. on some discount prop site, most are in the $379-$399 range for BPII.

 

[tmh]

Re: Proper WOT on upgraded 5.7L vortec engine.

btw, Walleyehed, are you affiliated with iboats? If so, then I'd be very likely to pay a bit more here than other online stores if need be to get the prop because of the assistance you've given me (and many others). I have bought a few items here over the past few years, but no props yet.

 

[walleyehed]

Re: Proper WOT on upgraded 5.7L vortec engine.

My main job is a Moderator on the forums....I do, however, do one-on-one consultations for props in situations such as this with the higher dollar, higher tech props.
I'll do some checking, but there should be no problem in getting you the BPII in a 20P.
Give iboats a call and tell them Stiletto #15420....see if they can fix you up, if they can't get one, I know where you can.

 

[tmh]

Re: Proper WOT on upgraded 5.7L vortec engine.

OK, thanks. I won't be buying anything for a while yet because I want to really test what I have and also sell some of my 15-19" props before buying a new one. I'll get back to iBoats when I need one and likely get the 20" or 22" Bay Pro 11.

 

[tmh]

Re: Proper WOT on upgraded 5.7L vortec engine.

OK, had the boat out for some testing today. here are the #'s. Just to recap, 19' open bow, heavy in the stern, 350 Mercruiser (280hp I think), Alpha One 1.65 ratio printed on outside of gearbox, I know they've been replaced, I assume still 1.65. My prop is a 19" Pitch SS, I think Quicksilver, likely lower tech bacause it wasn't too costly used in V.Good condition. I have Smart tabs installed, may need adjusting for new setup.

Test results. Boat planes in just about 4 sec, stays on plane down to maybe 20 mph. Good acceleration (not really great) throughout, WOT trimmed out 48.5 mph, at around 5000 rpm with a lighter than normal load today. Calculates out to around 13% slip, not surprising given it's a heavy, deep-V for a 19 footer.

Goals are good low end, especially staying on plane at lowest speed for tubing. I'd sacrifice some top end for this, but if more than a few mph i'd look for a compromise. Decent cruise speed efficiency also.

So....Walleyehed had discussed the Stiletto Bay Pro II 4-blade. I am leaning towards that one, but with new test info I'm open to other ideas. I think I'd try the 20" which may drop my rpm some, but Walleyehed pointed out maybe not too much due to less slip loss.

Does that sound like a plan? Any other ideas?

 

[Tail_Gunner]

Re: Proper WOT on upgraded 5.7L vortec engine.

He's probalby dead on. I know of a boat very much like your in size,weight and length..you probably will be quite happy with that prop id say it would run smooth as silk and hit 54mph...by the way nice boat...

 

[tmh]

Re: Proper WOT on upgraded 5.7L vortec engine.

Thanks for the input, TG. Is that a Mark Twain in the photo - looks like one. Is it yours? year and size?

Walleyehead, still waiting to hear from you to confirm your previous advise based on the new testing info. I guess i've heard almost nothing bad from Bay Pro 2 users, so it's looking like my #1 choice right now. I will likely buy something next week. when all my old props are finally sold (just sold #4 out of 5).

 

[Mkos1980]

Re: Proper WOT on upgraded 5.7L vortec engine.

When I had the stock 350 Mag 270HP we ran a Lazer II 21P It was hitting 4600 RPM's at 53.6 GPS. With 4 people It was turning 4400ish RPM's at 50.4MPH. Range for that motor was like your old one 4200-4600. Never had one problem planning with that prop. Popped right out of the water.

 

[walleyehed]

Re: Proper WOT on upgraded 5.7L vortec engine.

I'd stay with the BayProII in a 20P...
I've also ran the Lasers on quite a few sterndrives and unless the boat is light with a shallow V, The Laser doesn't have enough blade area to push the load, we've tried it and found it to be a much higher slip ratio than even a Stiletto 3-bld-which will walk away from the Laser on the same boat.
I don't think you'll be upset at any rate with a BayProII...I think it will do exactly what you're wanting to do.

 

[Tail_Gunner]

Re: Proper WOT on upgraded 5.7L vortec engine.

I'd stay with the BayProII in a 20P...
I've also ran the Lasers on quite a few sterndrives and unless the boat is light with a shallow V, The Laser doesn't have enough blade area to push the load, we've tried it and found it to be a much higher slip ratio than even a Stiletto 3-bld-which will walk away from the Laser on the same boat.
I don't think you'll be upset at any rate with a BayProII...I think it will do exactly what you're wanting to do.

Agreed i have a laser for sale.........Its like a gas truck vs diesel.... Unless you have a bass boat and that's whole different story. Or so say's WH ...

 

[walleyehed]

Re: Proper WOT on upgraded 5.7L vortec engine.

Check your PM box, TG....

 

[tmh]

Re: Proper WOT on upgraded 5.7L vortec engine.

Thanks again guys. I'll be getting a BP2 some time soon. I can't wait to give it a spin!