Re: 1995 Mariah 180 4.3L to 5.7L engine swap
Thanks for the comments. So you are saying that the alpha one generation 2 mercruiser i/o on my 4.3 is different from that of the alpha on gen 2 that was bolted up to a 305 / 350 engine in 1995 / 1996?
If anyone knows the gear ratio in a 4.3 alpha one drive versus the gear ratio in a 305 or 350 alpha one drive, I would be interested to know.
Regarding the prop, all we are looking for is getting out of the hole. My inital thought would be to go with a 19 pitch prop which from my understanding will make the boat slower at 4000 rpm than a 21 or 23 pitch prop.
SAS
for 4.3 is 1.84:1 for 350 it's 1.5 : 1. The difference is in the upper gearbox / upper half of the outdrive
That being said in my light little checkmate that I just converted from a 4.3 to a 383 stroker motor I still have the 1.84 gear in it. I'm breaking the engine in with a 29" 4-bladed cleaver prop that I had on hand and will probably need to run on the order of a 30" prop in something else to get it where I want it to be. I may end up swapping in the 1.5 ratio upper gear case that I have n the kitchen floor. My understanding at this point is that props in that range are good for 60+ mph in light boats, but that for heavier boats lower pitches are much more effective. Note also that the higher pitch props are harder to come by and are much more expensive generally speaking...
even before jets are right and prop / set-up worked through, given the throttle, my little boat blows right by 60 even with a prop that slips hard at the upper rpm range... and without getting the engine rpm over about 4700... it's built to run hard up to 5300 - 5500 rpm... even though that would most likely make a hand gernade out of the outdrive before long.
The other thing to think about is the engine you might be putting in. Was it built for a marine application? The engine I installed was built to be run hard in marine applications by a builder that does marine and race car engines for a living though. There are real differences if you're going to run one hard a typical street car engine won't last 100 hours... Think about taking your street car and running it up the side of a mountain hauling a trailer load of iron... at 4000 - 5500 rpms... all day long... The torque / horspower curves are different as well or need to be to get the best performance out of it and not destroy the alpha drive.
Also, my boat handles differently - a lot differently. I like it, but it is a lot more of a handful to drive with the bigger engine in it. Do you have kids? wife? that will be driving for skiers and so forth?
I do understand that you're talking about putting a nearly stock 350 in yours (note that specs matter a lot here... as in cam, heads, freeze plugs, gaskets, etc... and you need to carefully consider what you put in if you don't want to be doing it again in a matter of months) . Note that you're probably also going to want to go with a good aluminum exhaust set-up to minimize the weight difference (the factory exhaust is a huge weight and really does offset some of the difference in weight between the v-6 and v-8).
All that being said... of course you can do it if you want to... I'm not trying to dissuade you and I let my 13 year old daughter drive.... of course she has more brass and is more focused than many adults I know.
Oh, then there's the minor issue of insurance / liability and being in compliance with the coast guard tag... if that's important to you.
On the alignment tool... you should be aligning the engine / outdrive every time you pull the outdrive and depending on who's advice you listen to at least once a year...
drilling then engine mounts is no big deal IF you have the place to drill them. I had to rebuild the wood underneath and extend it (as in I had to fab new place for the mounts to go using glass, epoxy resin and wood) and then shim the mounts to get the alignment close before doing final adjustments on the motor mounts. If I remember right the holes for the motor mounts need to move forward about 4 7/8 inches, and the engine will be about 4" longer overall (as in where you need clearance in the front, top, etc...).
The ignition modules also have a different advance curve. The same distributer should be able to be used, but obviously cap rotor and so forth are different... it all adds up...
post a pic of your engine bay when you get a chance... It might not be that hard... just would suck to get all the way into it and have to spend a ton more money than you wanted to or have it not be nearly as usable when you get done...
Note on top off all that you can buy and set up a reman 4.3 long block that'll net over 220 horsepower for under 2k... with vortec heads, 4 barrel carb etc... and have a waranty. With gas prices the way they are that's not a bad option...
I would REALLY hesitate to trust anything about an engine where the mistake you mention above was made... My experience is that when someone is good... they don't make mistakes like that... if they're not, the rarely just make one mistake...
just my two cents... Hope this is helpful.
OH...
On props, if you are running a 21 now with the 4.3, use the same gear box and pit a 21" 4-blade behind it, you'll probably be able to stand that little boat on end out of the hole... and make it fly to pieces on the upper end... you would probably be talking about 24" - 26" prop or something like that... you could estimate where you'll be if you plot rpm vs gps speed for your boat above the speed where it is well planed out... what's your rpm and (GPS) speed at wot now?
Your current engine is probably somewhere between 180 and 220 horsepower... torque difference for the 350 will be big too and is really what matters more in a boat seat of the pants performance...
