21' Century Coronado, over rev.

[1980Coronado]

In July I purchased a 21' 1980 Century Coronado, with a 330 Hp 454 cid Mecruiser Inboard.

The tach is a little whacky at times in the low range, but i believe it's close enough on the upper end to tell me I'm over reving to easily with the current prop. The transmission is 1:1. Current prop is stamped 14" Dia RH 15" Pitch, but it's been X'd out and I believe reworked to a 14" pitch. It's a 3 blade NIBRAL prop...old school...not CNC.

Like I said my tach may be giving me bad readings and I need to hook a portable up to it to double check, but just using my ear I know the engine over revs too easily. I'm only getting 35 mph at 4500 rpm which is at about 3/4" throttle. WOT the tach will jump quickly towards 6000. Engine specs say WOT max RPM 3800-4200...that seems low to me but thats what the tag says. My guess is 4500 isn't going to hurt it....6000 will though.

This is my first inboard and I have no idea what prop this boat should have, or what Century recommended. I'm fairly certain the one I have should be switched out. It comes out of the hole well but I have no top end at all. We do some skiing and tubing, and we do load the boat up with people at times. I'm not looking to get the nth degree of speed out of it, but over reving is a concern. I do want to be able to load the boat and still get it up on plane.

Anyone have a clue what Century would have recommended for this boat? A 14" dia 14" pitch is too small for this 454 big block.

 

[1980Coronado]

Re: 21' Century Coronado, over rev.

Called A&A marine....this boat was sold with a 14X15. I'm guessing the prop was damaged and repaired at some point because I had to replace a bent prop shaft. It's possible that when they reworked/repaired the prop, they reduced the diameter as well as changed the pitch from 15" to 14". Put it all together and you get the over rev I'm experiencing. Need the weather to break and the Ice to melt so I can get the boat outta the barn and measure the diameter of the prop to confirm the theory.

 

[LakeGenevaCoronado]

Re: 21' Century Coronado, over rev.

I have a 1998 Coronado powered by a Merc Black Scorpion small block 330HP.I changed the original stock 14x15 Michigan prop for a 4 blade OJ Legend prop. It doesn't have the pitch stamped on it so I don't know the exact size. The local ski boat shop let me swap a few used props out at no charge to see what worked the best. Nice guys, didn't even want a deposit after I bought the blade puller!

I was blown away by the increase in performance from the 4 blade. It's been on there for 10 years now with the Michigan on the wall for a decorative spare.

Out of the hole, out of corners the boat is so much faster and more responsive. Do it do it do it. The Engine I have WOT's at 5400rpm which is dead in that range for the motor. Yours should run about 4400 WOT. It was the best thing I could have ever done.

I'm pulling the motor and trans this week the put new plates in the Velvet Drive. Should be fun! If you are interested in the original Coronado prop I would take it off the wall for you,

 

[1980Coronado]

Re: 21' Century Coronado, over rev.

I have a 1998 Coronado powered by a Merc Black Scorpion small block 330HP.I changed the original stock 14x15 Michigan prop for a 4 blade OJ Legend prop. It doesn't have the pitch stamped on it so I don't know the exact size. The local ski boat shop let me swap a few used props out at no charge to see what worked the best. Nice guys, didn't even want a deposit after I bought the blade puller!

I was blown away by the increase in performance from the 4 blade. It's been on there for 10 years now with the Michigan on the wall for a decorative spare.

Out of the hole, out of corners the boat is so much faster and more responsive. Do it do it do it. The Engine I have WOT's at 5400rpm which is dead in that range for the motor. Yours should run about 4400 WOT. It was the best thing I could have ever done.

I'm pulling the motor and trans this week the put new plates in the Velvet Drive. Should be fun! If you are interested in the original Coronado prop I would take it off the wall for you,

Sorry....I deleted my subscription to this thread because of the lack of response.

Wow ...you have a 98 Coronado? Century only built 5 Coronados in late 1997 as 1998 models. You have a very rare boat.

I might be intersted in your original prop....I'm going to call Eric Johnson at OJ on Monday and see what he suggests.

I would say that 4400 for the MIE 330 (454 big block) is a tad high for WOT RPM. I think the sticker on the engine says 3900 (way conservative).....I need to look in the Mercruiser manual and confirm it, but I think 4200 would be a good number. Thank you for the info on the OJ legend 4 blade...I was actually looking at a 3 blade OJ, but they don't make it in the 15" pitch as far as I can tell. Since you can run at much higher rpm with your motor, I wonder if the 4 blade is right for my engine. You are also getting more torque out of the 350 than I am out of the 454....which is counter intuitive, but true. Same horse power more torque, more fuel efficient...hard to believe.

I'll see what OJ has to say about the application....I may be interested in your original prop....would be interesting to see what the difference is from the reworked one I have. I did measure the diameter and it was reduced as suspected. Measures about 13.4", it's over 1/2" smaller in the diameter and is reduced 1" in pitch from the stock prop.

 

[LakeGenevaCoronado]

Re: 21' Century Coronado, over rev.

I would be happy to talk to you about the boat, I love it. I have been told there are 5 too.

Just pulled the motor out to rebuild the velvet drive trans. From what I hear it's easy. 13 years I never changed the fluid in the trans and boy we ride that boat hard. It did blow when I was racing someone pushing about 5600rpm in heavy waves with a full load so I can only blame meself!

Good friend in town rebuilds all the big marines props, brass, nibril, aluminum so I will ask him to size my prop for you in a week or so when I bring it in for the seasonal tune. I pretty sure the original is the same size as the ones used in the 80s.

The difference in a 4 blade is night and day coming out of a deep turn, out of the hole and pulling skiers. It also maintains a slow cruise very nicely. I highly recommend it and can't say enough good things about the change. The old prop I have is literally new out of the box. They put a new prop, shaft and coupler on for me in North Carolina when I picked up the boat. (Wife couldn't drive the inboard and hit something) Wrong rotation prop and didn't wire the shaft coupler bolts! Reverse was forward and the shaft pulled out into the rudder. The gave me the new prop I have with the right rotation but never used except to test the difference. Love the OJ but hate the name!

Cheers Troy

 

[1980Coronado]

Re: 21' Century Coronado, over rev.

Troy,

Check your PM's...I sent you a note about the original prop.

Yikes....never changed the fluid in 13 years I bet you'll change it in the future.

Yes they only built 5...go to the bottom of the page at this link:http://centuryboatclub.com/decade/fiberglass/fglcoronado.html

Ok...so I'm a little confused by your post.

You said:

I have a 1998 Coronado powered by a Merc Black Scorpion small block 330HP.I changed the original stock 14x15 Michigan prop for a 4 blade OJ Legend prop. It doesn't have the pitch stamped on it so I don't know the exact size.

Which prop doesn't have the pitch stamped on it? The original, or the 4 blade you're using now?

They put a new prop, shaft and coupler on for me in North Carolina when I picked up the boat. (Wife couldn't drive the inboard and hit something) Wrong rotation prop and didn't wire the shaft coupler bolts! Reverse was forward and the shaft pulled out into the rudder. The gave me the new prop I have with the right rotation but never used except to test the difference. Love the OJ but hate the name!

Ok...your boat was manufactured in Panama City Florida. So I'm guessing you purchased it new from a dealer in NC..right? The dealer had to install a prop, shaft, and coupling in the boat after it left the factory? The dealer put the wrong rotation prop on it, and didn't install the safety wire? This stuff isn't really all that important to this thread but I'm curious.

If your original prop is in fact a 14 x 15 RH 1" bore I think I may need it.

 

[LakeGenevaCoronado]

Re: 21' Century Coronado, over rev.

I bought the boat used in NC. It was owned by a someone else for 1 summer. Guy said he sold it because his wife can't drive an inboard and she wrecked the prop and shaft. It relates to the thread in that the rotation on my boat is unusual compared to most manufacturers. You are looking for a new prop and someone may try and sell you the wrong rotation.

I couldn't see the stamp on the OJ prop until I took it off this weekend. It's a 13x13. The nut covers the stamp.

I might try 13 years again. Ya never know. I put Amsoil in this time. The Amsoil marine remote bypass filter for the motor has been great. The trans rebuild was a breeze.

I am pretty sure original is 14x15RH. I'll pull it off the wall and check.

 

[1980Coronado]

Re: 21' Century Coronado, over rev.

Ah...ok that makes sense now. Hard to believe they put the wrong rotation prop on it....oops.

I understand the driving an Inboard issue...they don't steer worth a darn unless you're moving....ya gotta kind of aim em when pulling into the dock or lift.

Ok...now we're getting somewhere....this is a huge help to me...I appreciate it. Interesting that with your 4 blade both diameter and pitch are reduced...will be interesting to see if you did in fact start with a 14" x 15". It makes sense that the 4 blade is a smaller diam. and pitch due to the increase in blade area over a 3 blade. The unknown factor here is that your engine max WOT RPM is much higher than mine by 1000-1300 rpm. I need to confirm what my engine WOT max rpm spec is. I couldn't find the performance specs for my engine in the #3 Mercruiser manual this weekend. I believe it's marked on the engine.....but the boat is in a barn right now. I tried to look it up on-line but can't find it. I think it's 3800-4200, so 4000 may be a good number to shoot for under load. I may post this question in another thread. Maybe someone has access to these specs for a 1980 MIE 330-454cid Mercruiser inboard. The serial number I have for the motor is strange too. It doesn't match the range I'm finding on-line for that model. The number I wrote down 56252430. The serial numbers I see on-line all start with a 0 but have the same number of digits....???

Glad your rebuild went well! Like the dashboard on your boat....the wooden wheel is a nice touch.

Hey, thanks again for looking into this for me....this is a huge help....Let me know what you find on the original prop.

 

[1980Coronado]

Re: 21' Century Coronado, over rev.

I talked to Eric Johnson at OJ prop today and he suggested I start with either a 4 blade or 3 blade 14 x 16. He says the 14" diam 4 blade is actually 13.7 so the RPM should be consistent between the two. But, the 4 blade will pull better and run smoother....so decisions decisions. Leaning towards the 3-blade, but I'd always wonder what the 4-blade would do.

I'm still interested in your original prop if it's the right size.....PM me and let me know what you would want for it.

 

[1980Coronado]

Re: 21' Century Coronado, over rev.

Well...Since L.G.Coronado seems to have stopped checking in...was really hoping I could make use of his original prop....I went ahead and pulled the trigger on an O.J. 4Force 14x16x1 RH 4-Blade today. I can't say enough good things about Discount Inboard Marine....they're good people. If the prop doesn't perform well on my boat, they'll take it back. My gut tells me it's too much prop, but it's what O.J. recommended...so we'll see. I'll report back when I get the boat in the water in a couple weeks to try it. If it ever stops raining around here.....we could put the dock and lifts in.

 

[1980Coronado]

Re: 21' Century Coronado, over rev.

A 4 blade 14 x 16 is too big....3500 rpm at 40 mph WOT with just me and a full tank (light load)

 

[1980Coronado]

Re: 21' Century Coronado, over rev.

Update:

Took the day off Friday to help Dad splash his 28' cruiser up at Wawasee, then headed off to my boat on lake George. Took the new prop off (4 blade 14 x 16) and put the old 3 blade "14" x 14 back on. Took it out for a run and noticed that it was running rough. Hooked the tach up and could only get 3700 rpm out of it at about 39 mph. Went to Napa, bought all new ignition parts....plugs, points, condenser, rotor, and cap. Installed the new parts yesterday, reset the timing and wow......now the old prop is turning 3900-4000 at 41 mph and the engine sounds good. While the plugs were out we ran a compression test and found all cylinders were at 130-140 psi on an engine with almost 1100 hours. So.....after a fresh tune and using a digital tach it appears that I do not have a prop issue and I wasn't over revving the engine. I didn't put the 4 blade back on to check it, but since I only gained 200-300 rpm with a tune-up, I figured the 4 blade would have gained the same amount which would still be too low.

One interesting thing I found was someone had installed Champion plugs in the boat but they were not the correct number according to the manual. It could be that the number listed in the manual (RV8C) has been replaced by Champion, but we bought AC Delco plugs that matched the number in the Mercruiser manual (AC-MR43T). Doubt that this had much to do with the performance issue, the points were worn badly and the gap wasn't set correctly by whom ever did the last tune-up.

I guess the question now is which prop to buy. The prop on it now is running fine, but it needs replaced. It's pitted and worn, and was reworked by the previous owner. The diameter was reduced from 14" to about 13.6" based on my measurement, and the pitch was taken down from 15 to 14. I'm considering just going with the standard 3 blade in a 14 x 14.

edit: went with OJ recommendation of a 13 x 16 4 blade....supposed to give 300 more rpm than the 14 x 16 4 blade...we'll see

 

[LakeGenevaCoronado]

Re: 21' Century Coronado, over rev.

Sorry I haven't logged in for a while. Traveled to England and China and lost track of weeks. Can't even get on Facebook or Google in China!

Good to hear you have been trying different props. I do still have the new prop should you be interested. Just getting back to putting the engine back in mine and all the other bits that go with it. OJ 13x13 will surely be going back on. 52-5400 WOT depending on the load.

 

[1980Coronado]

Re: 21' Century Coronado, over rev.

Sorry I haven't logged in for a while. Traveled to England and China and lost track of weeks. Can't even get on Facebook or Google in China!

Good to hear you have been trying different props. I do still have the new prop should you be interested. Just getting back to putting the engine back in mine and all the other bits that go with it. OJ 13x13 will surely be going back on. 52-5400 WOT depending on the load.

Good to hear from you...glad you're back in the states.

As it turns out the prop I had on it, a reworked 14 x 14 3 blade, wasn't over revving the engine. However, it's time to replace it because it's worn, reworked, and pitted. I sent the 14 x 16 4-blade back, and they're shipping me a 13 x 16 4-blade to try. Everything on paper says it should work...we'll see. I'm hoping to get it Friday so I can put it on this weekend and try it out. Now that I know the engine is tuned-up and running properly I'm anxious to see what this new prop will do.

Get to work on that Coronado and get her back on the water....it's boating season if it ever stops raining! We got 3.5" yesterday....great weather if you're a duck!

 

[1980Coronado]

Re: 21' Century Coronado, over rev.

The OJ 13 x 16 4-blade works great....4100-4200rpm @ 44-45 mph. Comes out of the hole very well when loaded...I think I'm done tinkering