Merc 454s doing well?

PeterPalmieri · Post by **PeterPalmieri** » Aug 26th, '13, 12:52

So you guys know I've had kind of standing issues with the boat since I bought it 3 years ago. Outside of a fuel pump issue that is finally behind me she's running good. To go back a bit, season 1 I drove out to NJ and picked up a set of used props from Tony Meola. Ran the boat at 19kts assuming I'm burning 25 per hour, with old guages and no fuel flow meter I have never been certain. Last year I replaced the guages but could not get the tachs to play nice with the thunderbolt ignition. Just finally got around to putting a set of Faria tachs in, mechanic had them and we were just waiting for a reason for me to run the boat over to the shop.

Long story short I picked the boat up last Friday, the mechanic mentioned I might be over propped and we agreed we'd worry about it next spring (strange but I didn't worry to much). On my ride back to my slip I'm hitting 19kts at 2500RPMs. I'm by myself and have any empty tank so I take note but don't think to much of it. Saturday we go out with 3/4 tank 4 women, 3 men and 3 kids and I'm at 21.5 kts at 2650RPMs. Pull it back to 2500 and I'm at 19kts.

Now I'm thinking the tachs are way off I'm normally 19kts at 2800RPMs or at least that had been my experience. Called the mechanic this morning to confirm he took readings direct from the motors and the tachs are accurate. Great news as far as I'm concerned except my WOT is 3875 (Approx I didn't take note).

Does this all add up to you guys? Have I been overpropped since the beginning? It's kind of like I just found out there is no santa claus and I'm not sure.

Stephan · Post by **Stephan** » Aug 26th, '13, 15:19

Pete-
I have not done any thorough analysis... this is just my opinion.
Old carbureted Crusader 454s. I have not checked the tachs. The Crusaders are a normal and counter rotating pair with 1.52:1 gears.
I believe my boat is light with no generator, AC and the stock fresh water tank and a very small black water tank. The gas tank holds 204 gallons and filled the boat just gets the chines wet at the mooring. I also do not have any top or bimini. I have the small rudders and no trim tabs.
My props are three blade stamped 18X18 however the measure 17.5X17. We have spurs line cutters.
I believe the boat is under propped as the engines will run past 4,800 RPM if I don't pull them back. When I test I run them up to 4,400 and then only briefly.
When someone asks I will usually respond that I run 3,000 RPM and 22 kts at about 24 gal/hr. I need to know that I am - at least not intentionally - BSing the performance numbers.
What I have observed is running at 3,050 to 3,100 RPM (where I believe my 454s are as efficient as they will get just before opening the carb's second stage) I get 24 kts (GPS) in flat water. I believe I burn 22-24 gal/hr however it's not much more than a hunch or guess as I do the math in my head pulling away from the gas dock.
I am ready to accept that those engines + those props + a B31 should not return that performance but that's what I believe.
I hope this helps, just my 1.5 cents.
Stephan

Carl · Post by **Carl** » Aug 26th, '13, 16:30

Pete,

If your not hitting WOT and Tachs are correct you are overpropped.

Your performance numbers sound a bit better then they should be...although we do not have burn or WOT

Have a hard time getting out of the hole?

May want to check the calibration on the tachs.

Over propped that much is not a good thing for your motors.
You may love the speed...but you won't have it for long.

John F. · Post by **John F.** » Aug 26th, '13, 17:44

Pete-

I'm with Carl. f your tachs are accurate, you're over-propped. As I remember, I had 18x18 3blades and 17x15 4-blades w/5 cup (1.5/1 velvet drives). With both sets, I think she ran about 18 knts at 2800, 20 knts at 3000, 22 knts at 3200, and would hit 4200+ for WOT before one of the motors wouldn't run up anymore. As I remember, 454s should be propped to 4200-4400 WOT. Again, as I remember, my numbers were pretty close to others with 454 powered 31 FBC. Repowered 496s were lots faster. My 31 was pretty light too--bimini with radar arch, no genny, no fridge. I'd try to figure this out as soon as you can.

John

PeterPalmieri · Post by **PeterPalmieri** » Aug 26th, '13, 18:17

This is my third full season on these props so I'm guessing the tachs are off.

John I think if they were making 496 still I would have an easy decision in the future.

Tony Meola · Post by **Tony Meola** » Aug 26th, '13, 22:20

Peter

When I was running them with the 454's, the top side for me was 4200 RPM's. I was only doing 19 knots at 2800. I run light, no tower.

When you had the other props I believe you said you were turning close to 5,000 RPMs on the top side. That is way under proped. Could it be the cup on the prop has to be tweeked or the pitch.

Hate to say it but recheck the tachs under a load. Maybe Bob Lilco has a photo tach you can borrow.

John F. · Post by **John F.** » Aug 27th, '13, 05:02

Peter-

What size wheels are you running?

John

Stephan · Post by **Stephan** » Aug 27th, '13, 08:48

Can Pete just look for when the secondaries open as an indicator of how he's propped? If the engine is lugging shouldn't they open early?

PeterPalmieri · Post by **PeterPalmieri** » Aug 27th, '13, 09:00

This is enough for me to think the tachs are off, thank you all. I have a bent trim tab so I have to run over to the marina anyway, I'll have the mechanic check the props too, as we'll do a short haul to swap out the trim tab.

John F. · Post by **John F.** » Aug 27th, '13, 10:17

Stephan wrote:Can Pete just look for when the secondaries open as an indicator of how he's propped? If the engine is lugging shouldn't they open early?

I was thinking of that, but if the tachs are off by, say, 500 rpms, then the secondaries would open according to his tachs at about 2750 rpms (3250 rpms (about where my 454s opened) - 500 = 2750). If she's overpropped, and the tachs are accurate, the secondaries may still open at something like 2750 or whatever because, like you said, the motors are lugging. Makes sense to me anyway.

Carl · Post by **Carl** » Aug 27th, '13, 11:27

Stephan wrote:Can Pete just look for when the secondaries open as an indicator of how he's propped? If the engine is lugging shouldn't they open early?

I thought unless mechanical, the secondaries only open due to increased air flow that happens at higher RPM's...

Kinda difficult to figure anything out till you pin down another variable.

PeterPalmieri · Post by **PeterPalmieri** » Aug 27th, '13, 11:49

Since I have Tony's props on there and that end has never changed just the tachs I'm pretty sure they are off. I will check them and if they're not off then I'll worry about the prop.

CamB25 · Post by **CamB25** » Aug 27th, '13, 12:16

Did you relocate the tachs or place any magnetic items near them... magnetic compass?

Tony Meola · Post by **Tony Meola** » Sep 3rd, '13, 21:53

Peter

How did you make out with the Props/Tachs?

PeterPalmieri · Post by **PeterPalmieri** » Sep 4th, '13, 05:28

No progress yet while working on the deck.

Carl · Post by **Carl** » Sep 4th, '13, 05:55

I have a dwell tachometer I can UPS to you if you want to verify tachs.
I'ts at boat, so I'd need a day or so to get it.

PeterPalmieri · Post by **PeterPalmieri** » Sep 4th, '13, 06:40

Thanks for the offer Carl. When I get the deck done I have to do a short haul to replace a bowed tab. I will have them check when I'm there.

The bowed tab is a pain it happened during sandy. I bent it back and called it a day. It must have lost its strength and popped back to the bowed position.

Stephan · Post by **Stephan** » Sep 4th, '13, 09:04

Gents-
After reading this again, is there a chance that the tachs and props are OK and 1 engine is dogging it and that is preventing the other engine from making RPM? Pete- do I remember that at one time you thought you had to "rebuild" one of the engines?
I'm hoping it’s a little dip switch on the back of the tach or something...
Best,
Stephan

Carl · Post by **Carl** » Sep 4th, '13, 14:26

Stephan- thinking if one motor was dogging the other you would have one turning up more rpm. As only one set of WOT numbers were given I assume them to be even.

Pete- On Trim Tab...when you straightened the tab out...by any chance did you remove a lip or small bend making tab completely flat? A bend or rib adds a good deal of stiffness and support to otherwise flimsy sheet metal

PeterPalmieri · Post by **PeterPalmieri** » Sep 4th, '13, 14:31

I just pushed them back to be straight. I should have just replaced it then. Didn't remove anything.

Navatech · Post by **Navatech** » Sep 4th, '13, 17:37

I have an almost new optical tachometer you can borrow... Free of charge... You only pay the shipping...

Honestly though, I'd be surprised if the shipping didn't come close to the Harbor Freight cost...

It's the ONLY sure way of verifying that your console gauges are good...

PeterPalmieri · Post by **PeterPalmieri** » Sep 4th, '13, 20:01

Thanks for the offer. I have to haul the boat to replace the tab and the shop has one. Bit thank you both for the offer.

PeterPalmieri · Post by **PeterPalmieri** » Sep 16th, '13, 15:39

WOT 30.5kts

3900 port
3800 star

2000 13kts
2500 20kts
3000 24kts
2750 22 kits

John F. · Post by **John F.** » Sep 16th, '13, 16:25

Check the specs. for WOT for your motors. I think you'll find that you're overpropped by a good bit. Take your currrent and your wheels to a good prop shop and tell them where you need to be. They should be able to get you there.

Carl · Post by **Carl** » Sep 16th, '13, 18:20

Ditto what John said.

lobsta1 · Post by **lobsta1** » Sep 16th, '13, 20:06

Hate to disagree but my 1978 454 Mercs have a sticker on the valve covers stating that WOT is 3800 rpm. The Bertram owners manual shows Bert tested to that spec. My last boat had a 1984 Merc 454 & that spec was 4100 > 4400 rpm.

PeterPalmieri · Post by **PeterPalmieri** » Sep 16th, '13, 21:32

The tachs are dead on. The props came from Tony Meola who was running lighter than me when was using them.

The old tachs were a bit erratic so I was not aware how off I was. The original props in my garage are I believe 17x16 and when I surveyed the boat hit 5000 & 4900 WOT. Now knowing just how off the tachs were that may be bad info.

So the question is which prop should I play with? Or should I start with something new?

I think I remember 1985 merc 454 range of 4100-4400 but I can't find anything to confirm at the moment.

Tony Meola · Post by **Tony Meola** » Sep 16th, '13, 21:53

Peter

When you were turning 5000 RPM that would be too high for the engines, but if the tachs were that far off who knows. You could have been turning 5500. Before you play with the props, and it is a shame if you had pulled it over the weekend. you could have thrown the others on to see where you got to. I think when you initial put them on with the old tachs you came down to 4400 RPMs which would put you close.

Try going to the link below. Looks like they will help calculate based on engine year and manufacturer.

http://www.miwheel.com/propellers/prop-it-right/" onclick="window.open(this.href);return false;

John F. · Post by **John F.** » Sep 17th, '13, 07:45

Peter-

FWIW, I have a Mercruiser service manual (1987) that has specs. for a number of BBs. The WOT spec. is 4000-4400 for the MIE 340, 4200-4600 for the MCM 330 B/W, and the WOT numbers go up from there for the higher hp BBs. I don't know what the MIE, MCM, or other model designations mean. If you know yours, and its not one of the above, the manual may have it in there.

John

Carl · Post by **Carl** » Sep 17th, '13, 07:57

Peter,
You need real numbers or everything you do is a waste of time.

You now know your tachs are on...perfect.

You now what you are turning at WOT...perfect.

You know the wheels you have...perfect.

Last item in equation...you NEED to know the Rated WOT of YOUR engines. Then you can hit the prop shop and let them dial in your wheels to your boat and your motors so you can hit your rated WOT rpm.

How to find those numbers I do not know, mine have always been in the engine manuals...I have heard 454's WOT numbers all over the map...My best guess, grab the serial numbers off motors and call manufacturer or have someone look up the information....but taking numbers from memory or somebody who has a 454 in their boat is not the best choice in my opinion.

Motors can last quite awhile when run within specs...less otherwise.

PeterPalmieri · Post by **PeterPalmieri** » Sep 17th, '13, 13:32

John,

Seems like Mercruiser GM V8 engines were all wrapped into a single manual. Do they have specs for 454s? Do I need more detail?
If you can look that up I would appreciate it.

Carl,

You are right on, would be nice If I could modify my spare set and have them ready next time I haul which is likely for bottom paint in the spring. But with my luck I'm probably better off putting on the spare set, sending out the props that are on the boat and then pay for a second haul to swap them.

Thanks,

Pete

John F. · Post by **John F.** » Sep 17th, '13, 13:49

Pete-

The manual lists a number of 454. As above, the lowest WOT range was 4000-4400, the second lowest and most common was 4200-4600. See if there's a merc. model # on your motor and I'll try to look it up. If not, I'd prop to 4300 or so. Mine ran to 4200+ when they were healthy.

John

Carl · Post by **Carl** » Sep 17th, '13, 14:31

PeterPalmieri wrote: Carl,

You are right on, would be nice If I could modify my spare set and have them ready next time I haul which is likely for bottom paint in the spring. But with my luck I'm probably better off putting on the spare set, sending out the props that are on the boat and then pay for a second haul to swap them.

Thanks,

Pete

Mmmm no...if you are tweaking wheels...you need to give a clear picture to your prop shop of how boat is running with the wheels they are being given. That is they need the WOT RPM achieved, Rated WOT and its not a bad idea to give performance numbers throughout your rpm range.

Prop shop should verify wheels are correct, not banged, tracking incorrectly or marked incorrectly. They should look at cup and then go over what you want to achieve...best performance yet hit your rated WOT.

You take those wheels and you put on boat and hope you hit your numbers and performance is good. If still out...you do it again. If perfect, which should be doable as you are not far off, you have your spares brought to the same specs...and now you have backups.

Craig G · Post by **Craig G** » Oct 9th, '13, 07:20

Here is some more data to add in. I have a 1968 Bahia Mar with fuel injected 454 EFI MPs. My boat would seem to be heavy with a stainless steel marlin tower with hard top but no generator. It appears to be light though, as it sits high in the water, chines about an inch above water at stern with about half fuel. I believe it is over propped with 18 x 20s as I cruise about 20 knots at 2500 rpm. WOT is only about 3700 rpm but it gets out of the hole and on plane amazingly fast with no apparent bog down on the engines. I have even taken my kids knee boarding with it. I have a set of 17 x18s that I got from Mike Kennedy, but I believe they will be under propped, I am just now getting ready to try them out. I'm guessing 18 x18 would probably be ideal. How about everybody with 454s chime in with prop size and speeds/RPM?

CaptPatrick · Post by **CaptPatrick** » Oct 9th, '13, 07:36

Craig,

You can effectively increase the diameter of the 17" wheels by adding more cup to the blade tips. A medium cup will produce the same effect as increasing the diameter by 1".

Carl · Post by **Carl** » Oct 9th, '13, 07:58

In order to know if your propped correctly you need to know two things, aside from having a clean bottom and a well tuned engine.

You need to know the correct WOT RPM rating for your Motors and you need to know the WOT RPM you Motors will attain.

As long as you keep the WOT RPM's in the correct range you can play with the wheel style, design, make, blade count, diameter, rake, cup, pitch, edge prep and materials. They all can play a role in performance...but you have to be able to hit your rated WOT or accept the consequences of running over taxed motors.

Craig G · Post by **Craig G** » Oct 27th, '13, 07:33

[quote="PeterPalmieri"]WOT 30.5kts

3900 port
3800 star

2000 13kts
2500 20kts
3000 24kts
2750 22 kits

Those are similar numbers to my Bahia Mar with Merc 454 EFIMPs with B/W transmissions (approx 1.5:1) turning 18 x 20 props. I am about to install 17 x 18s and will give an update after installation.

Pete Fallon · Post by **Pete Fallon** » Oct 27th, '13, 11:57

Peter,
The majority of the gas 31's that I have surveyed have had 17" x 19 pitch 3 bladed nibral props, The 31's with 315 Yanmars have had 20"x 21 or 20" x 23 4 bladed nibral dyna quad props. On my boat an express I run 1997 454 TBFI (Throttle Bodied Fuel Injected) with 1:5:1 Hurth 8 degree down angle trannies, my struts and shafts have a low profile angle and are 1-1/4" Monel with 17"x 19 pitch. Wide open Throttle is 4400 RPMS @ 41.8 MPH , 3500 RPMS @ 35 MPH, 3000RPMS@ 30 MPH, 2500 RPMS @ 25 MPH. I don't have flow scans but based on a 3 day use with 172 gallons (full) I burned 110 gallons running at various speeds, wot, trolling, cruising and running back home at 3000RPMS for a distance of 110 miles over the 3 days. The most I can get them to burn at 4400 RPMS is 22 gallons per side, 44 total. It works out to an average of 1 mile per hour per gallon With my old carbed Chrysler 440's I was only getting 3/4 mile per gallon and burning 60 gallons for a 40 mile round trip. You could feel the boat lighting up as soon as the secondary's opened up.
I feel that you are over propped, make sure that everything is straight, struts aren't bent, rudders toed correctly, shafts straight, bottom fairly clean, trim tabs adjusted properly, cutlass bearings not worn and don't carry a lot of extra weight on the boat, you would be surprised how much effect a bent trim tab will effect the performance of the boat.
Good luck,
Pete Fallon

Craig G · Post by **Craig G** » Oct 27th, '13, 21:27

My Bahia Mar with Merc 454 EFIMPs has similar rpm/speed as Peter's does. That is with 18 x 20 props that have been on the boat for the 10 years I've owned it and however many years before that. Obviously my boat is over propped, but accelerates and gets up on plane very quickly. I just put on a pair of 17 x 18 wheels today that I bought from Mike Kennedy last year. I'm hoping to take it out for a spin tomorrow to try them out and will post the result. Hey Bertramp, do you want to go for a spin tomorrow morning?

PeterPalmieri · Post by **PeterPalmieri** » Oct 28th, '13, 05:23

She is over propped. I'm getting a nice 22kt cruise at at 2750, just waiting for the spring to make my adjustments. Trying to baby her for the rest of the season. With a full tank with 3 men and gear I'm around 20.5 at 2700 so she's not so far off.