mercruiser 2.5,3.0,4.3

88_rinker_v170

I own an 88 v170 with a mercruiser alpha one out drive. I have a mercruiser 2.5 at my shop but I checked the oil and I was milky. I pulled the head a stripped all the paint off the block and I can't find a crack the head and intake/ehaust gasket looked new. Is this just from sitting for years? It still turns over nice. I'm dropping it in my boat today and going to start rebuilding another engine for it. Should I build a 3.0 mercruiser or build a 4.3 mercruiser?  I have a 4.3 outdrive available so what do I do? If I build a 4.3 I need to figure out engine mounts and locate them. Also I'm missing a rail piece that goes on the right bow side anyone know where I can find these?

randy56

The 3.0 was a very good one, lasted for long time if maintained, They do not put them in boats anymore. That's the one I'd go with. IMO

88_rinker_v170

I have two good blocks for a 3.0 and a good running 4.3 that's why I am torn

212rowboat

i TRIED to kill a 4.3, and purposely... I failed... I still have the engine and outdrive (alpha one gen 2 1.82:1, which is also in great shape) strapped to a pallet in my shop... I ran the CRAP out of that engine, and to this day the compression checks out on every cylinder both dry and wet, with no leak down whatsoever in a ten minute span.. the plugs are perfect... the only problem is the ignition keeps walking on it, and it's either because of a lose timing chain or a worn dizzy... it doesn't walk that much, but enough to do some run-on after the key is turned off... other than that the engine is solid as a rock @ 300 hours, and the outdrive is solid too, only needing a new shaft seal... at some point, I'll list them as a package. 

88_rinker_v170

I'm located in Wisconsin though

212rowboat

they run the same in Wiscy, I'm sure..... 

where about?  I pass through there several times a year... I have a cabin in the U.P.. 

my point is that the 4.3's are abundant and very solid performers... you'd be hard pressed to find one capable of spinning a alpha one into the red, but for a rig up to 21 foot/3k# or so, they're hard to beat..... I've heard tales of some in the 250hp range that's done by simple mods, and I've encountered one with my own eyes that was dyno'd at 315hp that was being crammed in a Chevy LUV pickup in front of a 350T trans.   

88_rinker_v170

St croix falls area I'm 20 min north of the mn border

88_rinker_v170

Also I dropped the 2.5 in today and my rear motor mount don't line up

212rowboat

i'd call it the bell housing, but that speaks to another part on a boat equipped with an outdrive- but the thing that bolts to the block and covers the coupler- you'll have to get a compatible one.   I don't know if there are adapters around... It's never been something I've thought any about... @Alswagg?  what's the story, sir? 

88_rinker_v170

The boat came with a 3.0 I had a junk boat with a 2.5 pre alpha I found a new "bell housing" today so I guess that solves that issue I still need a shift cable and a wiring diagram for it 

randy56

Another thought, a 3.0 weighs 635 lbs and 4.3 weighs 845 lbs. A couple hundred lbs makes big difference in a 17ft boat