Switch motor from 3.0L to 4.3L. Is it possible?

glennfam2003glennfam2003 Member Posts: 7
edited March 2018 in Rinker Custom Projects
We have a 2001 Rinker bowrider 180 with the 3.0L engine that is gutless. I hear that there was a sport option that came with a 4.3L engine.  Is it possible to switch my 3.0L for the 4.3L?
What’s involved? 


  • Dude_HimselfDude_Himself Member Posts: 596 ✭✭✭
    The repower will require a whole new powerplant and it's exhaust, coupler, sterndrive, etc. If the sterndrive fits the 4.3 (depends on a few things) it'll need rebuilt at the minimum with new gearing and a different propellor. 

    Most economical way: sell your boat and buy the boat with the powerplant you want.

    Second most economical way: buy a donor boat with the 4.3 and frankenstein them together.
  • 212rowboat212rowboat Member Posts: 2,591 ✭✭✭✭✭
    edited March 2018
    it's not hard to do... 

    guessing your 3.0 uses the alpha1gen2, right?  just like a vehicle, the gearing can be done on either end (overall gear ratio on a car/truck is impacted by diameter of tire, which is roughly equiv to prop selection) - either through the drives gearbox OR through the prop.  obviously, the prop is the easiest and less expensive to do... for instance:

    if i had a gearbox of 1.82:1 and could swing a 21p prop within the engines spec'd RPM range, if i dropped to 1.5:1 i could likely only swing a 17p prop to meet the engine spec'd RPM range.  it translates to roughly the same forward speed, though... weird, huh?

    as far as the engine itself- you have to pull the 3.0 and PROPERLY fill the vacant holes in the engine mount blocks by drilling them out slightly, using a dowel of proper wood and diameter, then seal it... your 'new' engine will be hoisted in and sat atop the blocks, aligned to the outdrive as if you're doing a 'final alignment', then the feet of the mounts properly seated, marked carefully, engine pulled and new mount location drilled- return engine... it sounds hard, but it's really not.  

    seeing as how 4.3's are often swapped for V8's, you can usually find one pretty easy... you can find a gear box easily too- only the upper will gearbox will need to be swapped to find the ratio you need. but again, it can also be done from the prop, too, and which is the way i'd go beyond doubt.  cheaper, and easier.  

    as it turns out, i have an entire Alpha1Gen2 drive in 1.82:1 I'm willing to sell if you want it.  It needs a new seal, but that is all- it's in perfect working order otherwise.  I'd be happy to sell it to you, but................ prop, man- account for the ratio on the prop side. 
  • glennfam2003glennfam2003 Member Posts: 7
    Thank you for your response @Dude_Himself and @[email protected]. Sounds like we will be going with the same 3.0 L engine back in it.  If I am going to buy a used car engine, what year and model should I look for? 
  • pault1216pault1216 Member Posts: 206 ✭✭✭
    Just a thought...my understanding is that automotive engine blocks do not have the same corrosion protection as a marine type block. Car blocks were designed to have a closed cooling system using antifreeze and not typical raw water as most boats have.
  • 212rowboat212rowboat Member Posts: 2,591 ✭✭✭✭✭
    do yourself a favor and avoid the car engine... just. don't... it is a PITA.  

    i have a 4.3 sitting on a pallet right now.  it would need some top end work- such as carb and intake manifold, and it needs exhaust manifolds, risers, and elbows... you're welcome to it, though, if you want it.  it simply didn't have enough gogo for what i wanted.  it's an 05 Mercruiser... had about 300 hours on it when i pulled it.  shipping, and it's yours. compression is good and it ran fine when i pulled it- though i'd consider a timing chain and probably a water pump (engine mounted) if i was going to use it again.   I kept it with intent to use it as a stationary generator- but this is before i knew that power heads for a generator cost as much as an entire generator does- it's only in my collection because i kept waiting for a used powerhead to present itself... 
  • jhofmannjhofmann Member Posts: 430 ✭✭✭
    I used to work at a garage/machine shop where we rebuilt a lot of 2.5L GM motors, but I don't ever remember seeing a 3.0L. This may have been a 2.5L modified for marine use by either boring, stroking, or both. If that is the case, then the external components should be the same, but the internals may be different.
  • StodgeStodge Member Posts: 2,738 ✭✭✭✭
    I had a 18 foot Bayliner with a 3.0 liter 4 cylinder Merc motor.  It was a 2006 model.  Might have been marine special. 

    2002 FV 342 on Lake St. Clair - Past Commodore SHC - Vessel Examiner USCGAUX

  • Michael TMichael T Member Posts: 7,227 ✭✭✭✭✭
    ......I believe the 3.0 L OMC /Ford I had originated from automobile use.
  • jhofmannjhofmann Member Posts: 430 ✭✭✭
    I had a 2.5L in my 1983 SeaRay that was a GM block. I also found a used exhaust and riser from a 3.0L that bolted on to my 2.5L.

    I remember back in the day OMC using Ford 351 marine engines.
  • raybo3raybo3 Administrator Posts: 5,411 admin
    jhofmann said:
    I had a 2.5L in my 1983 SeaRay that was a GM block. I also found a used exhaust and riser from a 3.0L that bolted on to my 2.5L.

    I remember back in the day OMC using Ford 351 marine engines.
    Pleasure Craft Marine or PCM used Ford 351's I had twins in my Carver..... Just say'n
    2002 342 Fiesta Vee PC Point Of Pines YC Revere MA. popyc.org     [email protected]
  • prgrod01prgrod01 Member Posts: 53 ✭✭

    On a 180 the 3.0 isn't a bad engine choice, I have skied behind many boats with 3-4 people with decent performance. That being said I owned a new bayliner 180 with a 4.3 and was happy with it. I was however disappointed with the factory props, way to high of a pitch for a good hole shot and lower speed control. Once I changed the prop from a three blade 23 to a four blade 21 it made a huge difference. Lots of fellows go to the stainless 19 but I went with a happy medium for my driving preference. 

    With your boat being older, a tune up and engine compression check may be in order... are you getting the most out of the engine, is it healthy? Maybe a rebuild of the current 3.0 is in order vs swaping it out.

    2001 Rinker 242
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