Info on 165hp 250ci in line 6 cyl.
 

So I have this 1974 20 foot Sceptre it has the original 6 in it. I want this boat for a run about only. So I was thinking pull the 6 and go 5.7 or 5.0 but then I was thinking why. I am not building a race boat. But I would like to spruce it up the 6 a bit. Have any of you beefed up a 6 before? As well any one know the average WOT of a 20 I/o with the 6

I had that engine in one of my past boats (1977 Stingray) and loved it. Very dependable and easy to work on.

Jim

The old Chevy inline 6 is a reliable piece . There many parts available Clifford made intake manifolds 6=8 cams and such a lil research will bring a wealth of info. Contact the manufacturers for there advice on combinations for marine work ignition systems -going to a updated pointless design making spark more reliable . Exhast would likely be the hardest hop up design to find but I'd bet there's something out there. In the end it's just a air pump more in and more out = more power but it must work as a combination!

250 CI Iron Duke Mercruiser
 

I think they are probably one of the best sterndrive power-plants ever put together. Formula and Bertram put "pairs" of them in hundreds of boats and Cigarette used a pair them some of their "fishing" 28's. A single manifold and elbow cut down on the maintainance costs and they seldom developed enough torque to destroy a type one Mercruiser. You could "squeeze" two in an 8' beam hull and still change the starter motors without pulling the engine. They were part of the "Iron Duke" Chevy family of engines. When Mercruiser started using the 302 Ford block "888 Mercruiser" (V-8 - 188 HP) they became a little more popular in a single engine application than the inline six. Still there are many functioning today with marginal mechanics keeping them going.
Pontiac used that 250 CI block and built an aluminum Single overhead cam version with better carb's and put some in Firebirds and their LaMans' or Tempests. That very light motor would make 250 HP, I think out of the box.
I believe you would see something north of 40 MPH with one in a 20' Sceptre. (The 4 cylinder Mercruiser powered SeaFaris would go about 36 MPH) What a great "low budget" Ski Boat. Pelican knows about these motors and drives, maybe he'll chime in.

Terry England is this the Terry England that lives in Seminole Florida ? I think I would be happy with 40 knots this is going to be a run about as I have boat to fish from. The hull restoration will beat up my budget so keeping the power cost to a min. would be a good thing. The 6 that is in the boat turns but has sat for many years so a total rebuild is a must. Ty for the info

One potential issue with a V-8 or even a V-6, is clearance in the engine box. The 20' Sceptre that Strick redid originally came with a V-8, which he pulled and replaced with a bracketed outboard. I remember Strick commenting that clearance in the engine box was very tight, such that even changing plugs was a chore, let alone trying to change exhaust manifolds, risers or starter! Big difference in maintainability between a V engine and the I-6!

That said, the 3.8L GM V-6/Mercruiser seems to be a nice package, as I remember a Seafari advertised for sale with that package which was reportedly a 50 mph rig! Although the I-6 is probably heavier than the V-6, I think your CG would be further forward with the I-6, which would make it ride better!

That Depends on if I owe you money or not -
If I don't owe you money, then still I don't know anything about jumping cars at the railroad track crossing on 78 Avenue, Skiing the Narrows before Hamlin's Landing or Robyn Dalton. I don't know anything about racing Soap Box Derby cars down the hill south south of SHS on Vonn Road or Penny Chetham either. That was the other "Terry England" and NOT ME!
If I do owe you money than Terry England is just my "Nom De Plume" and my real name is Lee Pearce and I'm a bailiff with PCSO at the County jail.
Step Up, how would you know about that other scoundrel, vagabond, pirate and derelict who uses my alias? It's embarrassing!!!

I put a 5.7 in a 20 Bertram that originally had a 165 in it - with the 5.7 it was fast but I REALLY wished I had left the lighter/smaller motor in it; changing plugs was awful and usually involved blood, it didn't self bail at the dock, trimming it was hard, and it 'wandered' at idle with all that weight aft.
The only way to get more power is to move more air through. I am pretty sure 292 I6 block is the same as the 250 with a taller deck and longer stroke - it was a truck engine. I know they made marine versions that were about 200HP. You could also port and polish the head and if it is FW cooled you could go to a good aluminum intake manifold. A good roller cam in all that and you would be up well north of 200HP. It would be a project for sure.

California Bill has you covered.

https://www.amazon.com/gp/aw/d/19311...SGHRCZ8Y4X79R8

In the early-mid 50's the Chevy I6's were a staple of amateur drag racing and land speed cars. They were more efficient then the flat-heads and OHV V8's were new and not readily available in junkyards I imagine. I would have to think there is a lot of performance cross-over. And think of the cool names, "6 Pack", "Six-Shooter", etc. I say be different and proud of it.

Mercruiser 200Hp 1963-73 was the 292cid. Long blocks $2200: https://www.perfprotech.com/engine-g...product/247961
You would still need all the externals but I think you could use them from your 250cid. FirstMate Marine does the long block and should be able to help you with info on any externals you would need to replace.

The 292 is a long stroke engine and a 250 is more square which is what I would
want in a marine application.

Snort snort Delorean used a sohc head on the PMD sprint 250 motah which had a belt driven hot cam and a quadrajet carb.

The engine gained a reputation as a good performer at 250 hp, but the belts didn't last
and many failed at under 60 k miles.

As for your engine, I would take out the plugs and fill the cylinders with kerosene and ATF.
Let it soak for a week and turn it over to get the liguid out. Then spin it with an impact driver. Change the fluids and light her off. Then do a compression test. It may be in good shape.

Many engines sit for decades and can be brought back to good health.
If this is the case, I would then pop the heads off and check the extent of corrosion
in the jackets. The valve stem seals may also be dry rotted but that is a cheap fix.

if cylinders are rusted,valves are rusted - filling it with that cocktail is going to do what ?

you are aware that cylinder and pistons have a clearance spec ? also,no surface defects should be present on either area,yes ? notice we haven't touched on the valve train quite yet ?

spin it with an impact wrench ?

pop heads off ?


perhaps a better move would be to see if it actually spins over,with the plugs out - we'll skip the impact gun for this and substitute a breaker bar instead....turn it over a few times and see what happens


"step up" is claiming the motor's free:
"The 6 that is in the boat turns but has sat for many years so a total rebuild is a must. Ty for the info "


overhaul on that motor is going to be cheap - the "hang ons are the $ exhaust manifold,carb,electrical - I would count in as all hangon parts needing replacement...



are you not the same gentleman that was attempting to rebuild a 24 topaz a few years ago ?

no need to "beef" anything up
an inline 6 cylinder will NEVER wear out - no torsional vibration

lots of torque



but.....


smart play :

try and find a used 4.3v6 with a newer alpha gen II drive and transom plate - the space available in the motor box will be nice and parts are readily available for those 4.3's


way too many variables in an old power set up that's been sitting for years - read that as $

no need for 5.0 0r 5.7 motors in that rig...lots of big boats just sitting around - lower end "cock tail cruisers",like maxxum's,bayliners.rinkers - that were powered by 4.3 merc's - you can often pick these "donors" up for pennies
often times,these "cruisers" were fitted with the more desirable "bravo" drives - usually the bravo II drives - these drives are pretty much bulletproof....

might be a good avenue for you to explore....

I prefer a 1/2 ratchet for the first turns.
Said she turns.
Never owned a Topaz.

Not everyone has an open checkbook.

Is hangon a word in Jersey?

Put a brick on the gas pedal of Snowman`s 68 350 skylark with the wheel locked over.
Had one of the worst rod knocks I have ever heard.
Took 20 minnows to throw a rod.

Head bolt torque spec and pattern is 7th grade.
Pop Pop.

I am not an aerospace machinist and neither are you.

How do you file your rings?

"step up" - he owned a topaz



"hang on" - hang on parts,as I described them...


open check book ?? there's things that work and things that don't....a motor that's locked up,pouring a cocktail in it and attempting to "free it up" with an impact gun isn't the best approach - would you agree ??

could you point out where I made the "aerospace machinist " claim ?

one doesn't need to be an aerospace machinist to know a motor that's locked up from sitting,is going to need more than a "cocktail" of kerosene and ATF to make it useable...those areas of rust and corrosion,along with the left over debris - tell me,where does it go ? tell me,if the cylinder walls are pitted,from corrosion,what happens to rings as they grind against these areas ? tell me,if a valve stem rusts into an internal valve guide,what happens to that valve and guide ?

most often,these "backyard" "fixes" aren't the best approach....

that in line 6,it has one cylinder head....


above was said with a grin,watching Hillary take a beating ,sweating like a hooker in church...should I have said "hookah" ?

I6 i/o
 

I have a 1965 bow rider with a 230 ci 6 cylinder and mercruiser. Dad bought it new from Mr. Mosley, and I got it in 1975. I have put over 1500 hours on it, and it still runs very well. It is bullet proof. I put a freshwater kit on it in 1976, so that helped. With a 19 inch prop (large ears) it runs about 42 mph. I figure 6 or 7 miles to a gallon. That is with full fuel (28 gallons), and two of us (over 240 each). It has a type 1c merc out drive, which needs to be replaced. This is very similar to an alpha. I have a v6 with alpha Gen 2 I was going to put in it, but the engine cover would not fit without modification. You can buy manifold, breaker less ignition and most anything you need cheap. Hard to beat the iron duke!

Try reading post 11 again. Reading comprehension is clearly not your strong suit.

OP stated in post 5 the engine turns.

A straight 4, 6, or 8 only has one head?
You don't say. My head just exploded.

They say the best thing coming outta south Florida is 95 north.
Maybe you and Chris can carpool to Ft. Lee.

http://i245.photobucket.com/albums/g...psa9b79576.jpg

Mmm, hookahs.
Mmm, scallops.

`Tis best to dive when the grass is standing at slack tide.

my comprehension is just fine

my strong suit is repairing

not so sure about your's

let it go....

Poof.

This site is and has been about everything we love.

Boys-Boys-Boys....now behave or I will have to take your keyboard away from "y'all . LOL

Like mentioned Strick's 20 sceptre was crazy tight with the v-8 in it. Can't remember if he said if he thought it was original or not but still crazy to say the least. Mine originally had the 6. I did the bracket deal as well. It was a lot of work but a good learning curve for me. The motor may be salvageable, I wouldn't spend a ton of time if you plan on swapping out in the future. GFS idea would get you riding for cheep an let you check out the ride quality, balance of the hull and give you an idea of what you like or may want to do moving forward. Lots of donor boats out there for a swap and a rebuild if you got the mechanical ability wouldn't be a bad idea either. The 20 sceptre don't need much power to run and even with the weight of the cabin forward it can be acceptable to weight shift so be carful to what you do put in it or on it.


Starting to see a common denominator here...and no im not in math class

Sweet I damn sure appreciate all the input. I think based on the comments I am staying with the 6. This boat will be a bar hopper play boat. So 40 knots is plenty :-)

Step Up,
I think in the case of your Sceptre 20, I'd stay w/ the MC 165 also. Plenty of parts and Alpha drive compatibility. Excellent performance characteristics. I think 45 mph+ is doable. CC's bowrider numbers are amazing.

Only qualm I'd have about 4.3 is again pushing weight aft. Island Trader has a a nice link showing his engine well expansion on his 21, to accommodate a small block v8.

Like CC, I still have a 1965/6 Chevy 230 w/MC-1 sterndrive on my 21. I made the mistake of keeping the motor because it was sound, and fixing the out-drive when it became problematic. I repaired it be cause i was pretty certain the motor would not adapt to the Alpha drives. On the other hand the 250cc based MC165 will. In hindsight, I would have swapped for the more modern I6 and sought a 165 w/Alpha drive.

For my 21, the 292 sounds interesting. Is that longer stroker configuration effectively what the 383 stroker gets as a small block v-8? My guess is it would be a bit of a gas guzzler...

Gillie,

The only downside I can see with a stroker is that it tends to put more side load on the pistons, causing increased bore wear and potentially cracked pistons. (Sketch out the triangle created by rod and crank w/crank at 90 degrees to CL of cylinder, then increase the length of the crank throw, and you'll get the idea.) How much the rod angularity increases depends on how long the rods are. The SB Chrysler uses long 6 1/8" rods, so is a better candidate for a stroker than the SB Chevy, with 5.7" rods. Chrysler increased the stroke about 1/4" to get from a 318 to 360 V-8 with the same rods, but the 360 is very durable . . . last I heard the original 360 in NoBones' old Dodge Ram was still going strong at over 300K miles! I'm not familiar with the GM I-6's, but comparing the rod ratio (rod length/stroke length) should give you a good idea of the difference in piston side loading on the various engines. For reference, the rod ratio on the 273/318/340 is 1.85 and 1.71 on the 360 V-8's, so 1.7 is obviously good, although higher is better (= less side load).

Regarding fuel consumption, it certainly takes more fuel to feed more displacement at the same throttle setting, but the stroker motor will make more torque, so you can run less throttle/higher vacuum at the same cruise speed; the bigger engine may actually use the same or less fuel at cruise, depending on how hard you run it. The Moesly 21 "Unohu" that belonged to my friend Bob originally had the 150 hp I-6 MC 1 that was replaced after only a few years when the powder metal LU gears reverted to powder! He had also done several valve jobs on it, but this was before he learned to observe the 5" limit on manifold vacuum. The replacement 165 hp MC held up much better, but he only cruised at about 18 mph, I believe observing a 7" Hg min vacuum limit at cruise. When he installed the 260 hp/350 V-8, he was able to cruise easily at 23 mph at about 9" Hg. It's 100 nm to Walkers Cay from Palm Beach/Lake Worth Inlet and he typically burned about 37 gallons with the V-8 while I burned about 35 in the Seafari with the old 115 Evinrude, so his fuel consumption was about 2.7 nmpg, which isn't too bad considering he was carrying a typical Bahamas load with 2 weeks worth of groceries, etc.!

Mcgillicuddy, I am pretty sure the 230 i6 will hook up to an alpha out drive. I have an alpha transom plate for the inside and outside, and the engine fits. I intend to put an alpha on it as my 1c out drive has a corrosion hole in it, and the tilt hydraulics are beginning to act squirrel. Am I wrong? Do you know something I haven't found out yet. I bought a storm damaged boat front boat us (tree fell across gunnel) that had about 150 hours on it and has a v6 with alpha, but fitting the v6 looks like a job

Thanks Denny. Good insight, as usual.

cc,

I'm not 100% certain on what I said regarding compatibility. In fact, I mispoke. I have the MC 1-C EZ shift, which preceded the MC-1.

At the time my drive failed, I spoke with SEI and some Merc sales folks and they advised me of incompatability of Alpha. Merc mechanic said it would be problematic, but for all I know he was also the "service advisor." ;)
Difference may very well have been as simple the change of transom plates. :o

Mercruiser DID make a 250hp version of this motor for racing purposes. It was called, strangely enough, the 250/250. used through-hull exhaust and was coupled with the M/R drive. Carburetor was a marinized Rochester Quadrajet, but I don't know what the cfm rating was.

I've only seen two boats with this power setup.
John Allmand made a 19' back in 1968 for the offshore racing circuit (yes, intended to compete with the 21' SeaCraft), that was powered with a single 250hp 250ci motor. I don't think he ever finished a major race. We had this boat collecting dust in the boat barn, and I only saw it taken down once for someone to take photos of it.

Formula made the '69-70 23' with twin 250hp 250ci I-6 Mercruisers and they too, were, in fact, rated at 250hp each. Top speed was in the high 50mph range. We got one of these in at Waterway Marina in Palm Beach Gardens back in '84 with a bad motor, and we sent it across the street to Frank Brown Marine. As I recall, they gave it a new long-block because the motor had ingested water through the exhaust. I recall one of the mechanics saying he got it up to 58 mph during "testing".