replacing gas engine in my searay400db

Y

ynot

Member
Feb 14, 2010
132
s ca
Boat Info
400 sedan bridge
Engines
454 mer
i have a bad port engine in my 1996 400db its a 7.4 mpi mercruiser
need replacement ,and its not available anymore ,anyone had any experience with that issue
i welcome any opinion
thank you ahead
 
Do you have a usable block ? There is a place in Charlette NC that will rebuild it for very reasonable cost. I cant tell for sure but looks like maybe you are in California ? Surley there is some place there that rebuilds motors ?? Or does that cause cancer out there ?
 
I WAS TRYING TO GET THE MERCRUISER ORIGINAL AND THEY DONT MAKE IT ANYMORE
 
Don't get hung up on "Mercruiser Original" unless you have money to throw away.
 
You gotta love the boat to invest in a repower. Let's assume you do, and this is just a bump in ownership. 7.4's as OEM are as gone. Mercruiser had a repower program, but I haven't paid attention since 2017, so not sure if it's still around. Basically it was a cash for clunkers. You gave them your 7.4s. They trashed them, and sold you drop ins of 8.1 engines. EPA was happy, and you got much newer technology. If you had MAG MPI's they are probably MEFI-1. If you have Carb engines, some racer will want your other engine, or maybe both.
I lucked out (kind of) in 2017 when I found a pair of MEFI-3 1999 complete engines with 200 hours on them. why? Because they were in a LA Fire Department rescue boat. I'm thinking they spent most of their life being run on a hose, and serviced. The boat retired, went to gov deals, and someone in Sacramento bought it at auction. He managed to put the boat on a reef or rocks the first time out. The salvage team bought the boat at the ramp after a tow, and parted it out. What this set did for me, was get rid of all of my well used 1998 parts that had 13-1400 hours on them. I was getting murdered by those engines one hose clamp, or bolt on at a time. When my port engine finally got enough water intrusion and locked up breaking valves and what not on #6, I vowed not to just throw these old parts onto a new block. Now, the LA engines have had their issues (search other threads), but all in all I'm still happy with the find. I paid little enough that I could just throw them both away and start over with 8.1s. I may fall out of love with this boat before that happens.
Climbing off the crate now.......
 
thank you
i am thinking of replacing both engines .even though the other engine work extremely well last week checked compression and had 150 on all cylinders
i was thinking getting 7.4s from Michigan marine . same hp 310 /340 hp, don't know if more power will requires trans replacement or add weight on the boat .i would love that .most important is the torque produced by engine not really hp
my boat is in great condition i love it .its perfect for i want ...
 
Seems like a reasonable plan. Sticking with the 7.4s should be easy swap and I doubt anything other than new damper plates between engine and transmission would be required.

is this DIY or having a pro do the work? I would check around and see what they still like 7.4 or there is a good reason to go to the 8.1s.
 
If I was going to upgrade engines, I would consider going with Crusaders over Mercury. I like the layout of the Crusaders better.
 
didnt think about that ,wouldn't that involve more than replacing engines?
 
I went to a local engine builder this past winter for mine. He had a donor 7.4 gen 6 from a 1 ton truck with low miles. Cleaned up cylinders and built me a nice roller cam engine complete for $4100.00.
I pulled out and installed myself, runs great. May do the starboard this winter.
 
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