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Figuring out torque vs hp, and more...

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Old 10-02-2011, 02:08 AM
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Location: Huntington Beach, CA
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Default Figuring out torque vs hp, and more...

Hello everyone,

This is my first post.

I was searching around to see what torque my merc 260 hp actually puts out, and had no luck checking other post. Apparently, MercuryMarine thinks it is somewhat proprietary. So, I kept digging, I found this very useful formula:

Torque = H.P. X 5252 / rpm (5252 is a constant)

So I got my answer.

I wouldn't mind giving a background for what's brought me to this site for helpful info...

I bought a 1978 24' SeaRay SedanBridge, mercruiser 260 (gas), early alpha drive, w/ trailer for $6500 a few months back. I was very happy to get back on the water at a decent entry level price. To sweeten the pot, the seller held the paper for $2500 down, with the balance paid over the following two months. He had replaced all the upholstery, and included a good assortment of standard gear (in new condition). No anchor, new plank at pulpit, new forward hatch, original lower cabin windows filled and covered w/ black plastic covers. The wiring was a 'lil funny, with the running lights always on, unless batteries were turned off. It had a sizable bait tank just forward of engine compartment, that came about 15" above deck and 20" or so below. The 100 gallon aluminum fuel tank is placed forward of the bait tank, cased in foam, and decked with 3/4" plastic.

On my first voyage, I traveled solo from Huntington Beach to the bait receivers inside Long Beach break wall. The bait tank plumbing was definitely funky, filled with a 700 gph pump, with overflow draining through a large hose, over the engine, to a thru hull at the transom. The method to drain it was at a valve that released into the engine room. I was still happy with the tank size, and figure it held about 3 sport boat scoops, that live remarkably well. When under way, the intake thru hull for the bait pump would actually fill the tank without use of the pump. On the way back, I got it up to cruise. It would get to plane at about 2500 rpm, I pushed it as hard as 3200 rpm, for a short period. The trim tabs were a new feature for me, this is actually my first gas powered boat. On the first trip, on the way back, when cruising at 2500, the rpm came down progressively on it's own, I listened to the engine until it reached about 2150, and then I pulled it down. Perhaps my imagination, but I thought I felt vibration too. I reversed the prop, and found no weeds, I didn't see any line in the prop. I then got back up to cruise, and continued back to the launch ramp. I talked to the seller that eve., and mentioned the rpm episode. His best assumption over the phone was that the rpm was just varying from less torque, as a gas engine would, versus my experience with diesels only.

Fair enough. I changed the fuel filters just in case. I continued using the boat daily, for about two weeks, with just short trips 3 miles or so to the Long Beach break wall. Catching legal Calicos inside a protected break wall was good enough for me.

I got a towing membership, and felt safe to venture further. I wanted to see how she handled in some weather. I went solo, as I didn't want to be worried about other passengers. I crossed over to Avalon in about 15 to 18 knot winds, with a 3 to 4 foot sea. It didn't take long to decide it'd be best to go at troll speed. I went across at about 1200 rpm, slowing down when a 'good one' approached.

After being worked as a teenager, aboard the 1954 42' plywood boat, "Tortuga", for Mark Oronoz, I didn't feel too out of place out in the weather. The Tortuga ran out of Helgren's Sportfishing, in Oceanside, at that time. God Bless Dick Helgren. We used to fish commercial rock cod for 4 to 5 days at a time at Cortez and Tanner. Mark is down is Mission Bay these days.

My newly bought boat handled well, and I never felt threatened. I arrived at Avalon, and found an outer mooring available. I transferred my bait to a soft floating "receiver". I shuttled to town, had some dinner and Buffalo Milk, then retired for the evening. At about 4 am I woke, to find all my bait dead. However, I noticed Calicos swimming in the stern light, and proceeded to catch a full limit on fresh dead within the next hour, right from the mooring. I then headed back at about 2700 rpm, with the boat up on plane, in glassy conditions, and a soft swell. I tried a few kelps along the way, and sighted some Blue Whales. The engine was running fine for about 2/3 the way across, then the 'ol dropping rpm scenario started again. If I pulled it down, it would come back up and run fine for awhile. I got back, and was elated to see I only burned 35 gallons round trip to Catalina.

That afternoon I brought my two boys out for a local run. The engine started acting up more consistently. My heart dropped when I saw the foam under the oil cap. We were only a few miles out, the oil was just a little above the full line, so I took filler caps off each valve cover, and just left rags over the holes. I reasoned the damage is done, and perhaps I could help what water was in there evaporate out. We used to call this "making oil". I was about one quart over full by the time we got in. I questioned myself, did it get more water in the oil, or was it now just all settling to the bottom. I sucked the foamy oil out, which took all night for the West Marine hand operated pump to suck it out.

Next day I checked compression, changed the oil and filter, and putted around the harbor. (compression results were uneven, ranging between 155 lbs. and 95 Ibs.) It happened all over again, water in the oil. I drained the oil once more, filled the block with diesel, squirted fogging oil thru the spark plug holes, and pulled the heads. The head gaskets showed no obvious leak, the intake manifold was more suspect, rtv and all. The starboard head showed a valve stuck about 3/4" open, with a rusty valve next to it. Port head didn't have any major abhor rations. Out came the block. Dropping the oil pan showed an ugly mess of foam on EVERYTHING. What a mess.

I figured time for a new long block. The seller was nice enough to knock $1500 off the boat price, he's a good guy. Without paying marine engine prices, I figured out the real differences between a car and marine long block. It had 624 cast heads (junk). I decided on 487X cast heads, I could get with stainless valves for $650. I first wanted to open up the valve ports, but reasoned that it would need a larger carb. 35 gallons round trip to Avalon (50 miles) at up to 30 knots was good enough for me. The plan was to transfer the cam, or go with Comp Cams Marine Extreme. Besides that, get brass freeze plugs on a rebuilt block, preferably 4 bolt (existing is two bolt), and a marine head gasket (raw water cooled). An old timer has told me to use cast iron rings (his secret, and wouldn't tell me why. Perhaps softer with better seating, and water shouldn't be there anyways). I didn't want to re use the block, as it has been cooled with raw water for over 35 years.

Before I did all this, I wanted to know why this all happened, and started visiting online forums.

I found some useful knowledge about static water line compared to top of risers. Flat tappet cams need the top of riser at least 8 3/4" above the static water line, while roller cams needed at least 13" or 14". This was my first guess as to the source, with the extra large bait tank and all. Plus, SeaRay posted a notice for those years about how swim steps aggravate the problem with water coming up the exhaust. Somebody had added stallers at the top of the collectors, that didn't fit the oblong shape too well. Upon remove the collectors (removing the bell housing was a bugger by the way), I found the original stallers. The starboard side staller was intact, with the port side being melted to nothing, and gone. This didn't make sense as the starboard side showed the water intrusion.

Upon further investigating, I found my existing risers to be an adequate 14" above the static line. So, what brought the water in? Was it just the intake manifold?

Well, having the engine out, I turned my focus to the engine compartment. I found previous repairs at the port side engine mount, with some more repairs at the transom by the rear of the stringers. A little aggressive sanding helped me spring a leak. Eureka! I struck water with my boat sitting dry on a trailer. The previous repairs were shotty, water got in thru the repairs, and had no way to get out.

I ground out the false bottom straight to the hull. The foam was all wet. The thru hull was installed right thru the false bottom (a likely source to let water in). The port stringer was rotted out below the engine mount. Wood rot at the transom was all the way to the fiberglass at the drain plug. I dug all the rot out, and helped it dry out with a fan for a week or so. All the rot was replaced with cut strips of fiberglass that were impregnated with resin, and jammed into the voids. I re - glassed the entire bottom of the engine compartment, and layered up a considerable thickness of glass where I planned to install new thru hulls. Gel coating backwards (applying to final surface) is quite a bit more labor intensive than gel coating against a mold, by the way.

With most of that out of the way, I still pondered how water got in the oil to begin with. At this point, my reasoning is that the stuck valve cause a siphoning effect, and drew the water in thru the exhaust.

Last edited by funkyonion; 10-02-2011 at 03:27 AM. Reason: fixed typos
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Old 10-02-2011, 02:09 AM
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Default (cont.)

I have big plans. I have pulled the foam out of the compartment to port side of the engine compartment and forward, to about where the cabin starts. I cut a 1" X 7" scupper at the transom, and molded some 'glass for a hatch, with 3" tall curbs. These same curbs will go around the engine room. I want a dry cockpit set up, with a 6" curb at the cabin entrance. I cut bait tank flush to the deck, the foam all around it was filled to deck level with water, and leaking on the fuel tank, I pulled out the remainder of the tank and foam. I left the rear wall of the bait tank in place, to serve as a fiberglass bulkhead. That was today's project.

After looking at it, I think whoever installed the bait tank actually moved the fuel tank forward, to accommodate the desired bait tank position. If this is the case, it might help explain the sketchy "surfing" effect going down swell at speed. The fuel tank would have been brought forward about 2 feet.

I've been looking at some interesting trolling motors that mount on trim tabs, and come out of the water at plane. What a novel idea. To go one further, why not install a 4 HP DC motor inside the hull, with just the drive connected to the trim tabs? This would give me 3 screws for docking. You can literally move a boat sideways with three screws. I could also have stealth operation when wanted, and handy back-up propulsion, if the main ever craps out again. I started by seeing what motors I could find. A 4 HP continuous duty 12VDC reversible motor draws less than 100 amps. Looking further, I've found 8 HP golf cart motors that run on 48 VDC, with considerably less amperage draw.

I found a site that offers marine DC motors running on 144 VDC, with 148 lb-ft torque. While these might not be necessary for the side motors... Why not also use is as main propulsion, with an extra large prop (since rpm won't matter for torque, I do not have to worry about stalling the engine) Max rpm is 1000, but I can use a prop as large as 25"!

When I previously considered diesel, there is no real benefit for that size boat. Aside from the expense, mileage in either case will go out the window turning high rpm. But now I'm on a new quest. My gas powered arc welder can provide up to 200 amps at 12 volts, and the voltage is adjustable. That's one brief thought. I may just go diesel electric all around. I do not plan to load money on top of money for this venture, so I'm looking into how find a re power outside of the marine industry.

The fuel tank is most likely coming out. I drained the tank, and burned up the gas in my service truck. I plan to fill the tank with welding gas (happens to be tri mix; argon, helium, and Co2), and pressure test it. Somewhere I read only 4 lbs. pressure is necessary to test it, does anyone know if that is really the case?

With the fuel tank out, I could use bladders in the outer compartments, from just forward of the engine room to the cabin, on either side, with the vacated center compartment offering more cabin space up forward, and a true to life slammer from the engine compartment forward to the cabin. I do not believe stability would degrade, as the center would still have the weight from the slammer. Where the slammer meets the cabin I plan to install a full width bulkhead, I could make the forward side of it with 1" impact rated glass, and have one novel view from inside the cabin.

Well, I know this was quite an entry. I appreciate any one who might read or comment. The picture I attached to my profile (if it let me attach it) shows my photoshop version of how I want to improve on things. I look forward to updating anyone interested with later progress.

-Tony

Last edited by funkyonion; 10-02-2011 at 03:28 AM. Reason: fixed typos
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Old 10-02-2011, 12:36 PM
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Default more on diesel elctric

capttater shared a good link with me:

http://www.yachtingmagazine.com/arti...Electric-Drive
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Old 10-03-2011, 02:03 PM
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That may win the record for the longest first post ever...

Sounds like one heck of a project.
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Old 10-03-2011, 02:13 PM
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Quote:
Originally Posted by RT930turbo View Post
That may win the record for the longest first post ever...

Sounds like one heck of a project.
You read it all??? I was only able to read a few sentences before throwing in the towel!
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Old 10-03-2011, 02:56 PM
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You didn't get to the "144V Golfcart motor / gas powered welder hybrid; glass bottom sea-ray" part?

- Funkyonion... I think you may be WAY overthinking this. Throw a 350 back in it and go boating
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Old 10-03-2011, 02:59 PM
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Quote:
Originally Posted by funkyonion View Post

I found a site that offers marine DC motors running on 144 VDC, with 148 lb-ft torque. While these might not be necessary for the side motors... Why not also use is as main propulsion, with an extra large prop (since rpm won't matter for torque, I do not have to worry about stalling the engine) Max rpm is 1000, but I can use a prop as large as 25"!

But now I'm on a new quest. My gas powered arc welder can provide up to 200 amps at 12 volts, and the voltage is adjustable.

I could make the forward side of it with 1" impact rated glass, and have one novel view from inside the cabin.
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Old 10-03-2011, 02:59 PM
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Have you tried decaf?
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Old 10-03-2011, 04:00 PM
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Damn. You're not scared of big projects - talk about reinventing a propulsion system...


I'm with RT930t - put the 350 in it.

Last edited by apollard; 10-03-2011 at 04:03 PM.
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Old 10-03-2011, 04:53 PM
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Put down the calculator and go boating.

I'm with RT930t - put the 350 in it
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