Blown Mercruiser 5.0 Alpha. Low hours. Replacement options - Page 2

FishStretcher · #1 04-16-2015, 07:33 AM

Good luck! I am rather new to I/Os but I know I was warned about having sufficient height of the elbow in the riser in my 25. My local shop suggests a new flapper in the y pipe, too.

The extension to the riser is not that pricey for a raw water engine. They are a bit dear for a FWC engine.

Not sure if it is as big a deal on the 23 as the 25 as the engine likely isn't as low in the water.

FishStretcher · #2 04-17-2015, 08:26 PM

My MPI has no return and pump is on the engine. Water separator is on engine, too.

FLexpat · #3 04-18-2015, 06:58 AM

The biggest differences I am aware of to watch out for in a motor swap are the new style rear mount bushing and the new style wiring harness on late model MCM motors:

Mercruiser eliminated the spiral spring in the rear mount bushings in 2003 and changed the height slightly - that means the height of the fwd mts may change a little. Mercruiser service Bulletin 2003-11.
I can't remember when they went from the 9 pin round harness connector to the 14 pin connector but there adapters for that.

keith · #4 04-18-2015, 11:35 AM

Quote:

Originally Posted by FLexpat

The biggest differences I am aware of to watch out for in a motor swap are the new style rear mount bushing and the new style wiring harness on late model MCM motors:

Mercruiser eliminated the spiral spring in the rear mount bushings in 2003 and changed the height slightly - that means the height of the fwd mts may change a little. Mercruiser service Bulletin 2003-11.
I can't remember when they went from the 9 pin round harness connector to the 14 pin connector but there adapters for that.

Thanks for the advice. I currently have the 14 to 9 pin adapter on my motor, which is a 2007. I hope the motor mounts aren't different but I can deal with that when it gets in.

bobbert · #5 04-18-2015, 04:17 PM

Repowered my 23 with a 357 Mercruiser Reman. Was told by rep they used new blocks and bore over to make it a reman. They also add mechanical fuel pump. Bolted right up to transom ass'y. You would have to check the drive ratio to make sure you have a 1.47 set. The gear set is in the Outdrive.
I am very please with the set up. runs like a scalled cat.
If your interest in a 4.5 FWC MPI new left over call Marine liquidaters in Fort Peirce, they had one there in Feb. for 5500.

keith · #6 04-20-2015, 03:58 PM

Thanks Bobbert. The 357 reman is one of the engines I am looking at. It is either that or the 5.7 mpi remanufactured. I guess you had that choice too. How do you like the new motor? Any regrets not going with the MPI?
I have 1.62 gears and have been told that I can re-prop instead of changing them.

bigeasy1 · #7 06-15-2015, 11:05 AM

Quote:

Originally Posted by keith

Thanks Bobbert. The 357 reman is one of the engines I am looking at. It is either that or the 5.7 mpi remanufactured. I guess you had that choice too. How do you like the new motor? Any regrets not going with the MPI?
I have 1.62 gears and have been told that I can re-prop instead of changing them.

I also have 1.62 gears in my Merc Alpha I.(Tsunami 23) After some experiment with props of many sizes,I ended up going with a 15'-1/2 x 17 Mirage Stainless steel prop.it pretty much works perfect at all rpm ranges.

When I did my restore on the Tsunami,I had planned on going all new with a new engine and new outdrive.Unfortunately reality in the financials hit home,so I went with a donor boat that just went through an engine with a new long block 350 carbed Mercruiser.The guy sold it as the transom was shot,and didn't want to sink any more money into it.It only had 200 hours on it.

I almost hate saying this because I don't want to jinx it,but after 5 full seasons,it's been pretty much trouble free.Personally,I like the carb,(I used a 600cfm Edelbrock marine carb).I know that in an emergency I can rube goldberg the carb if I had a problem,but not so sure on the MPI,i'd probably be out of my league.
Also in the area I fish,virtually all the boats are either older I/O's or inboards,and the one shop I use is an expert on those systems.He also has all the parts on hand and is very reasonable.

Good luck which ever way you decide to go.

keith · #8 06-15-2015, 11:51 PM

Hey BigEasy. Thanks for the feedback and glad to hear your engine worked out so well for you. I ended up going with a 300 hp 357 MPI and it is great. Tons of power, smooth and quiet. I also need to reprop. I just finished the 20 hour break in so now I can figure out what I need. I currently have 1.62 gears and a 14 1/8 x 19 prop. I was at 40mph at 4200 rpm with a lot of throttle to go.

bigeasy1 · #9 06-16-2015, 07:47 AM

Quote:

Originally Posted by keith

Hey BigEasy. Thanks for the feedback and glad to hear your engine worked out so well for you. I ended up going with a 300 hp 357 MPI and it is great. Tons of power, smooth and quiet. I also need to reprop. I just finished the 20 hour break in so now I can figure out what I need. I currently have 1.62 gears and a 14 1/8 x 19 prop. I was at 40mph at 4200 rpm with a lot of throttle to go.

Glad it all worked out for you,I still would love to have something like you went with attached to a Bravo drive,but for now I'll have to stick with what I have.
I also remember being worried about the 1.62 gears,but Father Frank and the guys over at Prop Gods were a big help in prop selection.
In fact when I posted a thread about what size prop to go with,it turned into a fairly long thread about the advantages of those gears.I remember someone mentioning that Mosely preferred them over the 1.50's and other guys who raced did as well.My WOT is 4600 rpms(at least that's what I was told)for the engine I have.A few weeks ago on a flat day with the trim set just right,I was at about 42 mph(gps) at 4500 rpms.
That was with the canvas up which is like a big sail.I never run at wot,I try to keep it around 3200 to 3400 rpms.
If I can find that old thread I post it up just for the info.

bobbert · #10 04-20-2015, 08:25 PM

Just LOVE my 357. Gets up and goes, very economical. Picked the carb over MPI because we have big Ethanhol issues. Here it can run 5-14% and really does a number on the MPI.
This 357 is a Mercury motor, not a secondary builder. Hot run test, 2 year warranty, etc.

As far as the drive ratio, I would spring the bucks to change to the 1.47 ratio. You could diddle with the prop but it would be a compromise situation.

Buy the way it was a quick Drop in install.