GM inline 6 versus 302/188 ford

[pugsley]

Re: GM inline 6 versus 302/188 ford

No, I have not ran the boat. I bought it less than 2 weeks ago, knowing that it had a bad engine. As the previous posts stated, the owner stated that he ran 30 mph+ with it. Oddly enough,he is an aircraft mechanic. He noticed water in the oil and parked it in a barn thinking that he had blown a head gasket. Upon buying it I pressurized the engine and found no leaks indicating a cracked block. However, I found water on top of the cyliders and then checked the manifolds and risers. One was leaking.The other very badly rusted. I pulled one head and found rust. Head gasket was good. Thus, I made the statement that it was probably rebuildable. I drained the oil and refilled. The engine is not locked up. Soaked the cylinders, then hand cranked it, then cranked with the starter. Compression is bad on one cylinder.

I have had the 250/6 motors and had one rebuilt. Thus my curiosity in whether one would work for me being only 23 hp different. I bought the boat knowing that it needs to be repowered. If I need to drop a bigger engine in it, I will. I'm not concerned about resale. I like everything about it and intend to use it.

 

[pugsley]

Re: GM inline 6 versus 302/188 ford

BY the way, I am at approximately 700 feet msl. Yet I keep going back to the info about the boat posted here on iboats. Qoute: 1974 220 cuddy cabin;
This boat may have come with the following or other engines :
(In the interest of safety, never exceed the manufacturer's maximum horsepower rating for your boat.)
165 hp
188 hp
255 hp

 

[kilowatts]

Re: GM inline 6 versus 302/188 ford

Hi Guys:

Thanks for the comment Bruce. Sadly, I don't even begin to understand it, you've already lost me! As a totally untalented and untrained shade tree tinkerer who can only work on my engines with the manual in one hand and a wrench in the other, the previous comments were made on a "best guess" basis only. The conclusions came from High School memories of how to read a graph and I'm quite happy to be proved wrong. Usually a former mechanic friend gets me through the difficult parts when we have a few drinks and tell each other big lies about what wonderful people we are!
One thing I do know for sure is that I'm delighted with my Grew/Slickcraft and the entire MCM 165 setup. It works for me.

kilowatts

 

[kilowatts]

Re: GM inline 6 versus 302/188 ford

Hi Guys:

I think I run with a 141/2 X 17 pitch propeller at sea level. Last year I had 8 full grown people on board and the boat labored a bit to get on plane.

kilowatts

 

[blacksmith04]

Re: GM inline 6 versus 302/188 ford

I know that a stock 250 put out more torque then a stock 350 v8 back in the day. Very easy to work on too.

 

[pugsley]

Re: GM inline 6 versus 302/188 ford

My stock car racing friends said the same thing and is why they race with inline 6's. As to "HP is derived exactly from torque and RPM," well, while I'm sure that it is a correct formula which is way over my head. But it seems to me to ignore factors which would affect the development of rpms e.g. the load, prop slippage,prop size and pitch, and particularly the gear ratio of the outdrive. The 250 c.i. (4.09 liters) uses a 1.65:1. The 302 (4.95 liters or in essence 5.0) uses 1.50:1. The 305 (5.0 liters) uses a 1.65:1 gear ratio. Then the 350 5.7 uses a 1.50:1 just like the smaller 302. (888) So it certainly isn't just cubic inches or HP rating that is the determining factor, rather it is the power band or torque curve of the specific engine charactoristic. Otherwise these gear ratios make no sense. I admit that I may be full of it,by the way.
Again I go back to 45 Auto's "power required and power available" post, as well kilowatts torque curve and graph.
45Auto, are you out there? How bout a can o worms?

 

[bruceb58]

Re: GM inline 6 versus 302/188 ford

Again I go back to 45 Auto's "power required and power available" post, as well kilowatts torque curve and graph.
45Auto, are you out there? How bout a can o worms?

my bet is that 45Auto is going to tell you to stick with the V8.

And whoever thinks that a 350V8 has less torque than a 250I6 is wrong.

 

[FreeBeeTony]

Re: GM inline 6 versus 302/188 ford

I had an IL6 in a 20' Grady White. I wasn't very happy with the performance, I was only able to turn a 15" prop to achieve proper WOT.
The engine was very simple to work on, I rebuilt it in my basement.

Only had the boat for about 2 seasons and got 2 footitis.

I like the V8 option alot better!

 

[pugsley]

Re: GM inline 6 versus 302/188 ford

At wide open throttle I'm sure that the formula is correct. But under load (and all the other controlling factors) I'm not so sure, particularly functioning in a marine application. We are talking about low rpm power. The best explanation I have read, or what makes sense to me, is that running a boat engine up to plane is like driving a car or truck up a steep incline pulling a heavy load. The car engine is not going to work, or last. The same hp and c.i. rated engine with a different cam (power stroke) AND gear box will. Kilowatts post containing the torque curve shows a steep increase and then sharp drop off after 3200 RPM. Again power required to overcome the load resistance, and power available after that for acceleration. OR efficiency vs full developed hp at max rpm. So those that claim higher torque from the 250 are speaking in terms of efficiency in operating conditions at low rpms.

I think the gear ratio's in the outdrives demonstrate this. We have 2 5.0 engines with different gear ratios, and a 165 hp and 5.7 liter 350 at the same ratio's. The torque curve or power band must be the determining factors. Kilowatts has for him what is the perfect setup i.,e. it works for him. While he says that his boat is heavy, we don't know what it weighs. But the hull design is clearly a factor allowing him to get up on plane easily and run at speedsserving his needs with very good fuel efficiency.

As far as strict horsepower ratings, there is a lot of skullduggery in how motors are marketed and rated. I'm not a mechanic,auto or marine. But to give an example, take the huge bandsaw in my shop. It has a 2.5 hp motor. It operates at 240 volts AC on a 30 amp circuit. The motor weighs about 100 pounds and will resaw 14 inch thick hardwood lumber with a 1 1/4" blade. Now take my shop vac claimed to be 3.5 hp at 120 volts, or my supposed 3 hp router also running at 120 volts on a 20 amp circuit. If you want the formula, I can give it to you proving that these ratings are complete bs and virtual physical impossibility defying the laws of nature. They can not develop that kind of hp particularly at 120 volts. So much for formula's.....The router turns 22 k rpm thus the supposed hp rating. See how fast one will turn trying to take a deep heavy cut unto hardwood. Nice tool ..top of the line, 3hp my ***.

 

[kilowatts]

Re: GM inline 6 versus 302/188 ford

Hi Guys:

I think I'd like to add a final word;

My friend has a 1975 23ft hardtop cuddy into which we installed a rebuilt 165. His boat is heavier and longer than mine, has a hull with no reverse chines, no trim tabs or Doel fin and it performs like a swimming pig! There's nothing wrong with the engine, driveline or prop, but the characteristics of the boat leave a lot to be desired. It's a tail dragger but my friend goes crabbing around the Gulf Islands and is delighted with other aspects of the boat. He has no need for speed and indeed can't use it in the Gulf due to changing weather conditions so all the talk about stunning horse power and torque is truly meaningless to him as he hardly ever goes over 3500 RPM. It wouldn't be my choice but then again it's not my boat, eh? I will say that both he and I have truly enjoyed our time together rebuilding, reinstalling and having the odd drink (many drinks) together and for me I don't much care about the details.

Good luck.

kilowatts

 

[pugsley]

Re: GM inline 6 versus 302/188 ford

Right. It is about pleasure boating isn't it? Different strokes for different folks. I was not looking for a definitive answer. The question was will it get the boat up on plane. I think the answer is yes. The boat has dual horizontal chine flats on each side plus trim tabs. The other original question was whether it would perform for low speed cruising. I think the answer is probably but may be overworking the engine. Again I have no need or desire for speed, and in the waters we boat in most often it is downright foolish, rude to other people and fishermen in smaller boats or on pontoons, and just not our cup o tea.

These questions came about from iboats desrciptions of the 22 ft boat model. In checking again, the 24 ft hardtop, weighing in at 4400 lbs-another 1000 lbs- still says the boat may have came with a 165 going up to twin 165's. I have no way of verifying iboats posted information. IF it is correct, then the engine should suit my personal needs just fine. I would add that we very seldom take anyone boating with us. It is our time together. While I'm retired, my wife is not. She supervises 80 people and on her time, she reak lly does't want to deal with anyone. Its just us and the dogs. Plus we also have a 24 ft pontoon boat if we want to take friends. (50hp johnson, goes about 25 mph)

I sincerely appreciate everyones comments and help. These forums are truly great.

 

[Bondo]

Re: GM inline 6 versus 302/188 ford

Ayuh,... I agree, yer gonna be just Fine with it....

Just prop it to run 'bout 4200rpms at Wot, 'n Both of ya's will live long happy lives together....

I'm guessin' she'll be in the low 30s, mph....
Maybe high 20s...

 

[kilowatts]

Re: GM inline 6 versus 302/188 ford

Hi Pugsley:

How big are the dogs, though?

kilowatts

 

[pugsley]

Re: GM inline 6 versus 302/188 ford

Ha.ha, they're about a ton of fun. They're boxers. "Mr. Pipes" my "first mate" weighs about 75lbs and the other a little smaller. Can't say b.o.a.t. around him or he just goes nuts.... ready to go.