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Old 07-28-2022, 04:44 PM   #1
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454 crusader replacement

We have an 88 34' tollycraft sedan flybridge with twin 454 crusader direct drives. Thinking of replacing them with new 4.3 mercruisers and transmissions. Any opinions or thoughts on this would be appreciated. We only really want a cruising speed of around 8 knots and max of 10 or 12 ? The current engines run fairly strong and have approximately 2400 hrs, but the velvet drives are quite noisy and are a concern to me ? If I have to rebuild the tranys, it's a big job to get them out !!! So thinking of doing a major replacement ??
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Old 07-28-2022, 05:15 PM   #2
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Changing engines and gears to another type is expensive on a repower because of all the things that must be changed. How about keeping what you have and leaning on the throttles less? Even with big block gas engines, you'll save a lot of fuel if you go slower.
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Old 07-28-2022, 05:29 PM   #3
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Thanks for the opinion, we have only had the boat for one year and used it for about 100 hrs. Only run them at around 1500 - 1700 rpm and do about 7.5 knots. They are 34 years old and am concerned that the noisy transmissions will only be the start of many and more problems ? So a thought was to get it over with all at once . I know it will be a lot of work and money , but we love the boat and new power would definitely be a nice peace of mind ? Not sure at all if the smaller v6 is the way to go ?
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Old 07-28-2022, 05:35 PM   #4
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I'd be a little hesitant to de-power a planing hull to where it can't achieve planing speeds. Even if you rarely run fast, in some weather conditions the hull will be at its best at higher speeds (particularly in big following seas).

If the transmissions do start to show issues, Velvet Drives can certainly be rebuilt. As far as the engines, I'd give them a thorough check over. If they're not consuming excessive oil, oil pressure is good at idle when hot (after running fast for a bit and then slowing down), and they have good compression, I'd expect them to have plenty of life remaining (assuming good maintenance is continued and all of the bolt-on parts are kept in good shape).

FWIW, I routinely cruise at 6.5 kts / 1300 rpm with my 454s. They're not particularly efficient at that speed (smaller engines would be better), but it's still a lot more efficient than running around on plane.
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Old 07-28-2022, 05:40 PM   #5
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Welcome aboard. We were looking at a Formula 34PC last year that had big blocks in it with a lot of hours. If we had bought the boat I would have repowered it with new big blocks. I planned about $18K to have them removed and replaced with new engines from Michigan Motorzs. That would have been keeping the same transmissions. So the labor was estimated at about $4K. What you are talking about would require significantly more labor since the motor mounts would have to be moved, etc. I guess that it depends on what the boat is worth to you. I would look at maybe having the transmissions rebuilt. That would be in the neighborhood of $4-5K each but the labor would be very little. Maybe a couple of hours to get them out and a couple more to put them back in if the mechanic is good. Then run the big boys easier to save on fuel. I think the 6s would be more fuel efficient but I doubt you would ever make up the difference in cost. Unless the big blocks blow upÖ
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Old 07-28-2022, 06:23 PM   #6
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Greetings,
Welcome aboard. As others have said, keep the 454's and/or rebuild transmissions. At 100 hrs/yr, it would take (WAG) 40 years to recoup costs if you switch everything over.
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Old 07-28-2022, 06:35 PM   #7
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Maybe transmission oil analysis to get a sense on condition?

Good luck

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Old 07-28-2022, 07:41 PM   #8
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I wonder if 454 and 350 cid V8 engines have a difference in their engine mount locations on Tollycraft Stringers? Also wonder if Borg Warner Velvet Drive 71c and 72c trany have similar mounts. I have never heard answer on either question.

Reason I wonder... for you... is that our 34' 1977 Tolly tri cabin operates well and reasonably efficiently with 350 cid engines and 71c BG VD tranys.

If your 454s and 72c mounted same as 350s and 71s... you might want to consider that as alternative.

Best Luck!!

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Old 07-28-2022, 07:44 PM   #9
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Thanks for the opinion, the compression on both were very good when we bought it just a year ago, do not burn any oil, and have good oil pressure, they do seem to run strong and run well. we only took them up to 3400 rpm once for only a short time. all the rest of the time they are at idle while fishing on one engine or 1500-1700 on a cruise. Perhaps I will change thoughts as it now seems that my problem is likely the dampner plate on the starbourd side, the port is also a bit noisy ! I think it will be a large job, as I'm pretty sure we have to move the engine forward to get them out !!

Thanks again Rob
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Old 07-28-2022, 07:45 PM   #10
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thanks, already done this 50 hrs ago, results came back good with no issues.
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Old 07-28-2022, 08:40 PM   #11
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Why pull a good working motor? If the velvet drives need to be rebuilt its better then a season with pullin the motors and going smaller. If you do not go all out the HP needed to move will not be a drastic change with a lesser HP motor. IMO you will be running a lesser HP motor harder then you would a bigger motor to get the same results.
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Old 07-28-2022, 09:00 PM   #12
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bseabartender

Sounds to me you have a pretty nice power package... all in all. Might want to get an expert trany mechanic and see what may be needed.

In this Century's fuel costs... running a boat simply ain't very inexpensive.
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Old 07-29-2022, 12:06 AM   #13
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Since I have not seen or heard the engines and transmissions it’s impossible to give good advice specific to OP’s situation.

In general I wouldn’t replace a crusader 454/velvet drive. I would rebuild both. I feel the Crusader/velvet drive is the most dependable, simple, cost effective combination in the gas world.
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Old 07-29-2022, 01:36 AM   #14
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bseabartender, welcome to TF. I've taken the liberty of moving your thread from 'How to use the forum, etc,' to somewhere with a better subject fit, and therefore better coverage. ie 'Power Systems'.
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Old 07-29-2022, 08:00 AM   #15
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Agree with possible bad damper plate. Don’t repower the whole boat based on a guess. Get a real marine mechanic on board for a real diagnosis.
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Old 07-29-2022, 08:29 AM   #16
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Most Crusaders have a large rubber inspection plug in the top of bellhousing. Should be ez to just look in and observe condition of drive damper....often will generate noise if coil springs arranged around center are loose or some missing.

If the noise is a 'knock' at idle, it may be that transmission is in reality transmitting the noise of an engine miss....gear lash thru interrupted power flow.

If the noise is with both engines in gear, say when ideling out of marina, it may be just 'grumbling' of reduction gears due to idle underloading. To test, just pull one into neutral, thereby increasing load on other, and see if goes away....also a tell-tale of worn damper plate or plates.
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Old 07-29-2022, 08:46 AM   #17
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To add to Crux's post, even if things are healthy, you can get a horrid clank / rattle from a Velvet Drive at idle if the idle speed is set too low.
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Old 07-29-2022, 08:48 AM   #18
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Quote:
Originally Posted by tiltrider1 View Post
Since I have not seen or heard the engines and transmissions it’s impossible to give good advice specific to OP’s situation.

In general I wouldn’t replace a crusader 454/velvet drive. I would rebuild both. I feel the Crusader/velvet drive is the most dependable, simple, cost effective combination in the gas world.
I agree with tiltrider:

"In general I wouldn’t replace a crusader 454/velvet drive."

Although costly; I too believe you'd get the most bang for the buck... as compared to try and alter your entire power-drive line. Anyway, believe you mentioned the 454 engines test-out OK.
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Old 07-29-2022, 09:25 AM   #19
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Having rebuilt several I will add my 2c worth. Crusaders are some of the best built marine gasoline engines on the planet. Everything is heavy duty right down to the gaskets. You state in post 9 that they are in good condition and as others are saying you are going in the right direction looking at the damper plates. They are probably in need of replacement. The spring assemblies do corrode and fail with time. Everything you have is capable of being rebuilt when wear warrants, very economically. Fuel consumption will not improve much with re-power the biggest savings are at the throttle.
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Old 07-29-2022, 11:21 AM   #20
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Damper plates arenít that hard to replace if you can slide the transmission back about 3 to 4Ē. If they are going bad the springs can break and get into the gear teeth and lock up the engine. Much better to proactively replace them. They arenít too expensive as far as boating stuff goes. Does your engine have the 4 motor mounts on the engine or does it have 2 on the transmission? If they are on the engine then you can slide the transmission back on some really long bolts or allthread. You may have to slide the prop shaft back too. I am not that familiar with your engines but it shouldnít be that bad a job. I replaced my damper plates on our last boat but I had the engines out of the engine room at the time so it was really easy. I took a floor jack and a piece of plywood to support the transmission and rolled the jack back about 5Ē and did the swap. If you have the room to slide the transmission back the long bolts or allthread will support it while you change the damper.
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