replacing Mercruisers 7.4 454 gas engine in 400 sedan bridge

Y

ynot

Member
Feb 14, 2010
132
s ca
Boat Info
400 sedan bridge
Engines
454 mer
dear boaters
i need help in finding out if anybody replaced a gas engine 7.4 454 mercruisers in 400 sedan bridge
could it be done in water?
do they have to dismantle any part of the boat?
any advise will be appreciated
 
Get diesels if your budget allows. That's a huge boat to be pushing around with a gas motor. I am in a similar situation with a 380DA with 8.1's. We just filled up this evening on Clearwater Beach. Bill was a lil over $670 and that doesn't take us that far.

I dont mean to mess things up on your thread, it is just something to consider.

Best of luck Cap.
Vince
 
thank i appreciate your advise
i am retired budget is restricted wondering how will they be able to remove and re install the new one
 
haven't done it in your particlar boat, but had a dockmate do it in an older 370db in the water - took the old one out in pieces - then installed just the short block - four guys carried it on the boat and used a gantry built from 2x4s to lower it in the engine room - after it was all bolted in he added the heads and dressed the motor - this was obviously DIY and worked out fine - I doubt you could get a "professional" to do it this way.
 
Yes it can be done in the water. If you are going to have it professionally done, and you have a dock that the boat can be tied up and a truck backed up to the dock edge, they can use a truck crane to remove the old engines and replace with the new ones.

The sliding glass door is easy to remove for access. The ER hatches open up wide.

If you are going to go this route, a couple of suggestions. First, while you have temporary access consider removing and replacing the black water hose that runs down the port side of the engine room. Great opportunity and can be done quickly with engine out of the way.

Also, spend a little time and clean up the bilge area under and around the engines. Replace through hull hoses for the engines and AC while you're there.

Best of luck with it.
 
LattitudeAdjustment said:
Get diesels if your budget allows. That's a huge boat to be pushing around with a gas motor. I am in a similar situation with a 380DA with 8.1's. We just filled up this evening on Clearwater Beach. Bill was a lil over $670 and that doesn't take us that far.

I dont mean to mess things up on your thread, it is just something to consider.

Best of luck Cap.
Vince
Click to expand...

Two new diesels, transmissions, drivetrain, props, fuel tanks and rigging? Sheesh...that kind of budget screams new boat, not replacing engines :)
 
Stee6043 said:
Two new diesels, transmissions, drivetrain, props, fuel tanks and rigging? Sheesh...that kind of budget screams new boat, not replacing engines :)
Click to expand...


He still is looking at probably $24-30k for the gas engines. If I was on a fixed income.....I would be tempted to sell the boat and finance a used boat.
 
The hatches will open up in a 400DB for great access to the engine room and the sliding glass door comes out in fifteen minutes or so, which makes a large opening for the swap. Big blocks are close to 700 pounds. I don't think a couple guys could man handle the engines into the engine room since the large opening in the floor causes a footing problem. If you have a boat shop close that can pull the boat, do it. With a fork lift and long forks, the engines can be moved with ease into the cabin for lowering. It will be worth the cost of pulling the boat. I am a do it myself type guy and I am not sure I would want to tackle this project in the water. Drop one engine and it could spell disaster.

I agree with CaptRonn......degrease, scrub, change hoses, paint the floor, and make the engine room shine before the new install. Make it look like a work of art.

A 400 with gassers is probably a rarity.

Keith
 
PlayDate said:
He still is looking at probably $24-30k for the gas engines. If I was on a fixed income.....I would be tempted to sell the boat and finance a used boat.
Click to expand...

Seems high to me? I'd imagine reman's could be found for $4k each +/-? Some DIY, shadetree mechanic, I think a guy could keep it under $15k if he tried hard enough.
 
Thank you all for the suggestions
My starboard engines run great just the port engine the previous owner had issues with it’s a 1996 model
Great condition love the boat just that engine problem couple of years ago rebuilt the engine and replaced all heat exchanger gas manifolds with extended risers
I guess water damage the lower part and got worth so now have no compression on #5 cylinder and lots of scratches noticed via camera
Engine need to out
I hate to replace the other one runs like a bee
I was shocked when my mechanic told me that part of the roof top need to be removed
It’s a crazy thought that is why I needed all your thoughts and experience in that matter
Now make it a great boating day
 
It can come out the door, but you will need a setup like this:

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midexp said:
Really???? 30K is high for diesel.
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Plenty of threads on CSR with the actual costs to repower with gas or diesel. If he only needs to do one engine then probably about $12-15k for an engine he can count on. Keep in mind.....we also have a lot of CSR threads where owners tried to go cheap, the engine failed and the mechanic was nowhere to be found.

In the end....it is the OP's boat but a diesel repower on that boat would run over $100k (Engines, Transmissions, Fuel System, upgraded shafts & shaft tubes, props, engine controls and the boat has to be out of the water).
 
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