Info on 165hp 250ci in line 6 cyl.

[flyingfrizzle]

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

[Step Up]

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 :-)

[McGillicuddy]

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...

[Bushwacker]

Originally Posted by McGillicuddy

. . . 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.!

[cc]

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

[McGillicuddy]

Thanks Denny. Good insight, as usual.

Originally Posted by cc

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

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.

[Fr. Frank]

Originally Posted by Terry England

...
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.

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".