LS Swap Seafari 25

[Xcomunic8d]

Purchased a Bravo 3 with counter rotating props yesterday from a guy on another island. Had a friend go look at it and pick it up. Seems to be in good shape. I’ll be tearing it down when it comes but $800 was a steal.



Engine is all the way down. All apart, cranks out, pistons, all of it. The oil galleys have been tapped for the vvt/Afm delete. The holes are 5/16” so a 3/8-16 tap with 3/8 set screws with thread sealant is perfect. Make sure to use thread cutting oil the block is hard.

Tap these pedestal looking things:



But you’ll have to clean this out of everywhere. The valley plate has sensors on it that deactivate these weird looking lifters.







Engine will be going to machine shop for the works:
Cleaning
Block decked
Main bearing alignment and honing
Camshaft bearings aligned and replaced
Pistons cleaned, ringed, and checked hopefully not replaced but who knows.
Block honed and overbored if necessary
Heads to be cleaned, valve job, and shaved .030 to bump up compression on 243’s
Gotta find somebody who balances cranks for bob weight etc.

Will post pics when I can.

[flyingfrizzle]

Originally Posted by Xcomunic8d

Yeah that terminator x looks to be best way to go. I haven’t figured out the gauges yet. I wanted twin lowrance screens tied together on the outboard. But I’m leaning towards just analogs now. I just want this done.

Sounds like you have a great project too. Don’t forget about that throttle body... I’m going cable drive. And a 102mm vs 92mm adds no hp on dyno according to Richard holdener.

I’d get one of those Fast Lsxr intakes if I could afford one. Sharps custom intakes look great too. But I have the TBSS which is identical power to a LS3 intake and the best OEM you can get. I just can’t justify $1k for 30hp.

PS check out that F35 cam from Texas speed for your swap. It won’t work for me but oh I wish it would.

Yea, the terminator x is really economical compared to the dominator or HP. The digital dash is really over priced especially the 12.3" that I got (got mine 20% off on Holley deal days over the holidays). The little 7" display is not to bad cost wise and you can catch it on sale too somtimes but I don't know how well it would hold up to the salt or marine environment.
Far as my build, I would like to do a billet intake but may just end up with a holley high ram for now. For the throttle body I will probably go the 102 or 123mm due to we are trying to support 2000+ hp. I have TKM right now building the rotating assemble (stage 3 LSR) solid aluminum block, Callies magnum crank, GRP aluminum rods, custom full skirted turbo pistons and it will have to top fuel hoops (solid ss fire rings with copper head gaskets). Similar sister stage three engines they have done made over 2300 with a single 98 mm turbo which had a little smaller back side than mine which is a Forced inductions 98mmx116mm built by Jose. Cam is a custom grind spec from Kevin Mullins at TKM for the application running Methanol on billet atomizer 700s. It is going to be a full tilt race motor so not the common LS stuff. Love to do a mild LS in a seacraft though, I think that would be a really good fit for a 25 seafari. Looks like yours will be plenty strong for the 25 with the 243 heads. Should make a nice piece.

Picture and link to an article below of the sister engine. Mine will be based off of it with a few variations...hope to have mine ready this fall.


https://www.dragzine.com/news/john-d...m-dyno-record/

[Locke N Load]

I just want to hear a 500 hp straight-piped (assuming no mufflers) LS in a boat. I bet it will make the hairs on the back of the neck tingle.

[Xcomunic8d]

I expect so. I’ll probably soundproof and heat shield the cover I’ll make for it. And maybe put some inline mufflers to it. But I expect it will sound incredible.

I’d like to have it quiet when I’m out fishing but every once in a while let her rip. Not sure how I’ll do that tho. I can’t find any affordable captains call exhaust setups.

Until then here’s a preview. But mine’s gonna have a lopier idle.

https://www.youtube.com/watch?v=2AVoeVyvws8

[Locke N Load]

Originally Posted by Xcomunic8d

I expect so. I’ll probably soundproof and heat shield the cover I’ll make for it. And maybe put some inline mufflers to it. But I expect it will sound incredible.

I’d like to have it quiet when I’m out fishing but every once in a while let her rip. Not sure how I’ll do that tho. I can’t find any affordable captains call exhaust setups.

Until then here’s a preview. But mine’s gonna have a lopier idle.

https://www.youtube.com/watch?v=2AVoeVyvws8

https://www.amazon.com/Electric-Exha...ts_id=15726591

Just saying...

[Xcomunic8d]

So block came back from machine shop awhile back.

The pistons were badly out of spec. Something like .009-.010

Just placed order for engine parts a little over $2k not including terminator x and exhaust manifolds.

Have the following on order from summit:
KGB-mb5013xp Main bearings
KGB-cr807xpn Connecting rod bearings
Slp-h1132cpa pistons, wrist pins, and snaps
Mah-41859cp piston rings
ARP-234-6301 connecting rod bolts
Clo-9-3658tx3 timing chain
Clo-9-5417 timing damper
Mah-95-3561 gasket kit
ARP-134-1003 cam bolts
ARP-134-1501 timing cover bolts
ARP-234-2503 crank bolt
ARP-434-1202 exhaust header bolts stainless
Sdm-pce229-1006 flywheel
ARP-330-2802 flywheel bolts
Sum-htlskit2 ls7 lifters and trays
Sum-141560 trunnion upgrade

Already have arp head bolts and summit brand main cap bolt kit.

Planning on getting exhaust manifolds, raw water pump at marine engine depot.
Planning on getting terminator x 990-505 through Amazon or Holley directly.
Local Mercury dealer is sourcing a bravo transom assy and timeline. Looks like sept.
Outdrive is scheduled for rebuild/reseal 7/26 in shop.
I have a plan for heat exchangers on the closed cooling system more to come on that.

Will keep parts list updated and pics as is relevant.

[FLexpat]

I love it but don't go too crazy on that build!!!
I think the straight back Bravo 3 is limited to about 450 ft-lbs torque unless you do some upgrades. Another thing to watch is how deep you mount it - I know you can get drive extensions (0.5"-3") but I don't think you can get a shorty lower for the Bravo 3.
This might be useful: https://www.go-fast.com/Mercury-Merc...uction-Changes

[Xcomunic8d]

Thanks I’ll look into that. Most of that parts list is the heavy duty parts to handle prolonged higher rpm than car engines experience (main bearings, connecting rod bearings, heavy duty bolts, etc). I’m trying to make a how-to as there aren’t many out there and I want a simple list for the next guy who wants to do this.

The dealer was kind enough to tell me merc’s suggested mounting point of 13 9/16” up the framing sq from keel of boat. That’s the center point for the template to cut out drive hole. I’ll need to mark that and compare the centerline of flywheel and the A/V plate on foot to keel. I’ll measure it out and let you guys know how it’s going.

I was told 600hp was max. I was worried I wouldn’t have enough torque but my bravo3 has a 2.0 (we think) gear ratio. We’ll know more once we tear it apart, inspect and reseal it. It’s the older style without the swept back design. My local dealer told me it’s gonna max out around 55-60mph depending on rpm and be an absolute torque monster with dual prop and 20p blades.

The cam I’m planning on running is a tsp212/218. 437hp @6200 rpm, 418tq @ 4800rpm. I plan to high speed troll 13-20mph most of the time. Other than slightly ported heads, and maybe a bigger TB, there are no other power adders.

I’ll be mating it up to the 454 coupling on flywheel to help mitigate the chance of shearing the coupler apart. Those things are pricey.

I think I finally solved the raw water pump mounting issue to the crankshaft. Hopefully I’ll get through to guy I need to speak with tomorrow.

[Xcomunic8d]

So parts are coming in left right and center. I haven’t taken pics of each one b/c how exciting are piston rings and main bearings? I figured you see them installed.





Here’s more hand valve lapping.



Using your water pump bolts can be very helpful to install the cam. Also it’s useful to reach around behind to guid it in for the last 2 cam bearings.



Here’s my 12yo son putting in his first batch of lifters.







So the exhaust manifolds come in Monday. The majority of raw water system comes in tonight at some point.

I ended up ordering the exhaust manifolds from Hardin marine b/c they ended up being cheaper. The marine engine depot guy told me I had to pay more for O2 sensor bungs and it was not in a kit. I did however get most of the raw water system there.

[Xcomunic8d]

So I caught a mistake when I was reviewing my project. And trying to order a Holley terminator x. The timing set I ordered is compatible for a 1x sensor not a 4x sensor.

i 2 day aired a different cam sprocket in. It was a BTR.

Wrong sprocket for my gen4, 58x reluctor 4x cam sensor:



right sprocket



I tried to break my collarbone yesterday so my son is installing the second head under dads close supervision. I was helping some older friends pack and move off island. I had just repaired the bumper on their avalanche. I was up to my elbows in grease and filth due to rain and conditions. I went out back fo wash off. I went one way and mud went the other. My shoulder landed squarely on a lava rock. Boy that hurt.




torquing rocker arms









the exhaust manifolds are here and look awesome. That’s a follow-up post shortly with more research I did and info that will help the next guy.