swap. 350 for 305

MikDee

MikDee

Banned
Joined
Jun 6, 2007
Messages
4,745
Re: swap. 350 for 305

Well, regarding the boats I've had pre 1990, Then I'd say that My 78' Mercruiser 305/228hp, my 79' Mercruiser 350/260hp, and my 1986 OMC Cobra 4.3 V6/205hp were rated at the crank, because some of them were rated higher then what this info shows. I'm sure these newer engines actually do produce as much as, or more power then, those previous engines because they are rated at the prop.

I'm talking oranges, and you're talking apples, or vice versa. Either way we're saying the same thing.
 
K

krisnowicki

Lieutenant Junior Grade
Joined
Jul 11, 2007
Messages
1,172
Re: swap. 350 for 305

well its in. Me and a friend pulled the 350 and put the 305 in. I got the whole deal It is a plug and play. It is marked at 230 or 228 horse power 305. As to before it would plane with almost no throttle Around 1800 rpm... he even gave me another alpha out drive included in a price of 1100... Awesome deal. I did swap to a 19 inch prop 19 x 14. I do have one question. I didnt have a pig tail connecter before and this engine has one. I had all my wires individually going to each component. But now I would like to hook it up with the pigtail . When I was at the techs shop he kept saying I need a 10 pin plug but ... I counted and there is only 9 holes inthe round plug on the engine. I have looked around and seen online a 9 pin plug. Is this just a standard engine plug?
 
K

krisnowicki

Lieutenant Junior Grade
Joined
Jul 11, 2007
Messages
1,172
Re: swap. 350 for 305

Also the outdrive I got did not come with a pin that connect the trim rams to it. Whe could I get one of these should I go an get a stud from lowes or something.
 
QC

QC

Supreme Mariner
Joined
Mar 22, 2005
Messages
22,783
Re: swap. 350 for 305

The 9 pin actually shows 10 positions as there is no 9. I guess they don't want anyone confused about the 6 and 9 . . . Standard Merc connector.
 
U

Uraijit

Banned
Joined
Feb 5, 2008
Messages
884
Re: swap. 350 for 305

whywhyzed said:
would $1400 or so buy a used 350 truck vortec motor from the wreckers and leave $ for gaskets etc.? or am I out of touch with used engine prices?.....
brass core plug set is about $25
Click to expand...


Yeah, $1400 is enough to do a TON of stuff to a salvage-yard block. Around here you can pull an engine from pull-it-yourself type place for about $150+$30 core.

Summit Racing has a brass freeze plug set for $13.95. If you want, you can go ahead and re-ring the pistons for $20, get a "marine cam" for $150, then you can do roller rockers for another $100-$150. Brand new timing chain $30, High-Volume oil pump $25, complete engine gasket set $50...

That puts you at about $560.

Hell, throw in a set of Hypereutectic pistons for another $85, get some roller lifters, for $200

That's still only $845. Might as well get some nice machine work, like a new valve job, and a port and polish, replace all your bearings... Then you're getting close to your $1400.00
 
MikDee

MikDee

Banned
Joined
Jun 6, 2007
Messages
4,745
Re: swap. 350 for 305

Kris, What brand, & type, of boat do you have? This was my boat a 79'- 20' SeaRay bowrider, Mercruiser 305/228hp 4bbl. with a 14X19" pitch Merc Alum. prop., But it was a freshwater boat (Candlewood lake Conneticut) before I got it, to run in salt water, no bottom paint, and I put thru-hull Ex. on it.
It would regularly do 45mph, trimmed out 48mph, and once with a new exact replacement prop, did 50! Here is what my boat weighed engine included, I don't know how your boat compares?
"http://www.nadaguides.com/default.aspx?LI=1-24-38-5697-0-0-0&l=1&w=24&p=38&f=5698&m=1466&d=1600157197&y=1979&ml=S&gc=MR&gtc=MR"
 
K

krisnowicki

Lieutenant Junior Grade
Joined
Jul 11, 2007
Messages
1,172
Re: swap. 350 for 305

I have a four winns liberator 201 it is 20 feet 1 in. it wieghs about the same.. 100 #'s off... How was it as far as plane(ing)? I use it for fishing alot and some tubing or wake boarding.
 
MikDee

MikDee

Banned
Joined
Jun 6, 2007
Messages
4,745
Re: swap. 350 for 305

Nice boat! I wanted one of those but, just couldn't find one reasonable enough when I was looking. Anyway, if I remember correctly, mine always came right up on plane, about 2k-2200rpm, but I had a gas tank towards the middle. I don't remember if I had a Doel fin on it or not? some of my boats did.
If you're boats a little heavier then mine, you may need a 17" pitch prop for the right rpm range. One more thing, make sure you give that motor plenty of break in time, and go easy with it during break in, if it's new. I also ran mine on synthetic blend oil, but I don't know if this is good to do, till after break in. Good Luck, Mike

P.S. You're hull design has a deeper vee then mine, Good: better riding, Bad: you scrub a little speed.
 
K

krisnowicki

Lieutenant Junior Grade
Joined
Jul 11, 2007
Messages
1,172
Re: swap. 350 for 305

sounds good.2200 should be fine. I have one out drive with a whale tail the other without. The one with out is newer and sounder so I am putting that on. I will post pictures / videos with results.
 
180shabah

180shabah

Rear Admiral
Joined
Mar 26, 2005
Messages
4,995
Re: swap. 350 for 305

imported_John_S said:
4.3L non-vortec 2brl: 155hp
4.3L non-vortec 4brl: 175hp
4.3L vortec 2brl: 190hp
4.3L vortec 4brl: 205hp

SM #18 all @ prop

Some Pre-Vortec Specs: (1994 tech manual)
http://www.boatfix.com/merc/Techbk/94/94hg1a.pdf

Vortec specs: (1997 tech manual) does not include 305, which did come back in '98
http://www.boatfix.com/merc/Techbk/97/97hga1.pdf
Click to expand...

Unlike the V8's(2 versions), there are 3 different "versions" of the 4.3.
-Vortec (all are balance shafted)
-Non Vortec w/ balance shaft(power ratings listed above)
-Non Vortec w/o balance shaft(power ratings similar to the newer Vortecs) That balance shaft eats approx. 30hp, but the non shafted engines shake pretty good at low rpm's.
 
J

John_S

Rear Admiral
Joined
Jun 21, 2004
Messages
4,269
Re: swap. 350 for 305

"Non Vortec w/o balance shaft(power ratings similar to the newer Vortecs) That balance shaft eats approx. 30hp, but the non shafted engines shake pretty good at low rpm's."

What year did the changeover occur? If it was mid-80's or earlier, then some of that 30hp was in the crank to prop ratings conversion. or if you know which Merc manual covers it, will look it up this evening.

Add: Well, it doesn't look like I ever downloaded the V6 manual prior to #18. 18 only goes back to 1993.
 
J

John_S

Rear Admiral
Joined
Jun 21, 2004
Messages
4,269
Re: swap. 350 for 305

"it looks like the balance shaft motor was introduced in 1992:"

Which would make sense on why #18 starts at 1993. There is usually a 1 year lag from vehicles to boats. At least that was my impression when looking at different changes to the SB and when they came out on Mercs.
 
180shabah

180shabah

Rear Admiral
Joined
Mar 26, 2005
Messages
4,995
Re: swap. 350 for 305

John S - looks like you got your date one the balance shaft.

MikDee - that is a great "history" on the 4.3, although I should probably amend my statement above from 3 versions to 156 possible variations (+/- 100):D
 
180shabah

180shabah

Rear Admiral
Joined
Mar 26, 2005
Messages
4,995
Re: swap. 350 for 305

There is also a camshaft change between these engines.

1991(per tsb above, I don't have FSM for those years)) - lobe lifts .234(int) and .257(exh)
1993-1997 - lobe lifts .269(int) and .273(exh)

Neither cam is radical, but 15%(int) and 6%(exh), increase in lobe lift or 22.5% and 9% increase in valve lift should have made a difference. Of course, there is also overlap, duration etc. to consider, but don't have any of that data, so I guess it is possible that the cams ultimate power potential are equal. Who knows?
 
MikDee

MikDee

Banned
Joined
Jun 6, 2007
Messages
4,745
Re: swap. 350 for 305

shabah, It's mind boggling the combinations, No?

john, that 2nd link you put up is for a 3.8V6 the predecessor to the 4.3, I'm guessing the 83' in the link means a 1983 motor?
 
J

John_S

Rear Admiral
Joined
Jun 21, 2004
Messages
4,269
Re: swap. 350 for 305

I fixed the link above.

The cam changes are probably from flat to roller based lifters. On the SB the hp did stay the same.

I see where that the hp in '85 did equal today's vortec (205) and close on 2brl. A good part of that would be the conversion of the rating. I was hoping to find a SB that would have provided a before and after conversion adjustment for all engines. Didn't find one. ):
 
You must log in or register to reply here.
Top