Idea of speed?

[cdn1972]

My new boat an aluminum boat 14 feet long pointed deep V front end and a flat back end. It is rated for a 25 hp. Any idea what speed range I would be in using a 53 bigtwin 25? The boats weight is 225 pounds.

 

[Texasmark]

20-25 mph. Plenty of fun was had with 25 and 35 hp Big Twins back when I was a teen and first getting into boating on my own. Fiberglass boats, new then, and plywood boats 15-16' with a couple of occupants could pull a skier or two, if kids on two skis, fast enough to enjoy it. Without the skis they would take you to a fishing spot and back home in a flash....fast enough to want to slow down in a good chop and quarter the waves.

Aluminum boats of that era, in my neck of the woods, ran 7 ½ ( which would plane out the boat.....barely with an adult driving and 3 young kids)....with them going forward to get it on plane. 10 hp engines on 14' aluminum rental boats were a popular choice and what we had (to do) when younger. An 18 would push one nicely which I had on my wooden 14 footer when I was in high school. Didn't have a car, had a boat. Used mommas '51 Ford 2 door custom with the newly out Ford-a-matic automatic tranny.

 

[JimS123]

Your boat is a standard V Hull, not a deep V. Or it could also be called a semi-V.

My 220 # woodie with a '53 Big Twin 25 will do 25 mph GPS.

Nice motor, it runs very well, but it's VERY loud and sucks gas like there is no tomorrow....LOL.

 

[cdn1972]

Ok thanks for the correction on the V hull. Previous owners family member who inherited the boat told me. After redoing the boat next spring im hoping to get the rebuilt bigtwin to power it. I was hoping on flat water to hit 30mph on my gps but if it tops at 25 that would be ok too

 

[Texasmark]

Your boat is a standard V Hull, not a deep V. Or it could also be called a semi-V.

My 220 # woodie with a '53 Big Twin 25 will do 25 mph GPS.

Nice motor, it runs very well, but it's VERY loud and sucks gas like there is no tomorrow....LOL.

Yessirree on both counts. Merc was the worst on noise and best on gas and OMC was touted as the "quiet" ones but the cubes (35 cu in displacement) gave them the ability to push big fishing rigs.....and you had to fill up those cubes with gas...wink! When OMC did the Triump 55 hp triple looper back in '68 I thought I died and went to heaven! No more cross flows for me.

Jim, you have a beautiful restoration there. We didn't have Lymans in the Houston area back then. Yellow Jacket and Holmes were the top two with Lone Star leading the Tinnies.

 

[cdn1972]

Just thought of something..........are these engines as easy to prop as my 1967 Merc 35 was. I could easily change props and pull a skier or zip across the lake with another. Now different boat, This ones aluminum and the past boat was glass much heavier then this one but both 14 foot. I had three diff props for the merc and each easily defined what was possible for the pitch etc. Are the bigtwins this way too or are there less choices?

 

[Texasmark]

Michigan wheel supplied after market props back then and OEM was aluminum and MW had bronze, and surely alum.. Back then, unless you were looking at a 2 bladed racing prop for a Quicksilver direct drive racing lower unit, most props of which I am aware were conventional designs and pitches were rather shallow, most OMC being 3 bladed......like 25 hp pushing a 10" diameter prop at a 2:1 gear ratio couldn't stand much pitch.....google Michigan wheel and look up props for OMC 25-35 engines. As I recall up to, maybe through, the 40 hp OMC used the alternate firing 35ish CC twin engine design running at 4500 rpm max. Memory kinda fuzzy here. There is a www site that has brochures from back then posted on the web and you can look up specs for most any popular engine, especially US available engines in that time line. Forget the name.

OMC was a cotter pin and a "shear pin" (er ah drive pin) and off comes the hub and the prop. Merc had the nuisance tabs that you bent to lock......but as I recall no shear pin to shear when you needed it most......relied on the rubber hub to slip. Had both and never had a problem with the Merc props driving when you needed it.

Edit: And never had to lift up the lower unit to clear weeds from the forward protruding gear box casting that Mercury avoided with a nice smooth faced gearbox molded into the lower unit that easily slid over moss and obstructions and all. Another wink for Merc. of the day.

 

[JimS123]

Yessirree on both counts. Merc was the worst on noise and best on gas and OMC was touted as the "quiet" ones but the cubes (35 cu in displacement) gave them the ability to push big fishing rigs.....and you had to fill up those cubes with gas...wink! When OMC did the Triump 55 hp triple looper back in '68 I thought I died and went to heaven! No more cross flows for me.

Jim, you have a beautiful restoration there. We didn't have Lymans in the Houston area back then. Yellow Jacket and Holmes were the top two with Lone Star leading the Tinnies.

As a youngin' sitting on Grandpa's dock I always knew my first OB would be a "quiet" 'Rude. The Mercs were just too noisy. But now after having run a couple of the same era, I'm not so sure...LOL. They seemed quieter back then. Now I know for sure I don't want a '50's Merc.

My second OB was a Triumph and it was the second year of production. It WAS a fantastic motor, idled well and ran quiet. Had it not been for all of the problems with the electric shift I might still have it.

My Lyman is not "restored". It meets the ACBS criteria of "Preserved". All the wood is original and it has never been sanded down to bare wood.

 

[Texasmark]

As a youngin' sitting on Grandpa's dock I always knew my first OB would be a "quiet" 'Rude. The Mercs were just too noisy. But now after having run a couple of the same era, I'm not so sure...LOL. They seemed quieter back then. Now I know for sure I don't want a '50's Merc.

My second OB was a Triumph and it was the second year of production. It WAS a fantastic motor, idled well and ran quiet. Had it not been for all of the problems with the electric shift I might still have it.

My Lyman is not "restored". It meets the ACBS criteria of "Preserved". All the wood is original and it has never been sanded down to bare wood.

Wow on the Lyman......great find.

I bought a new Johnson 125 in 1972 with the electric shift and power tilt as trim wasn't available till the '73 model. I kept that boat for 7 years and other than fuel mix, I did absolutely nothing to the engine other than replacing the alum prop (that I managed to bang up every Sunday afternoon). I think 1973 was when the Stainless Steel Teflon OMC prop became available and I bought one....remembering $185.....lots of bucks back then. We boated every week and sometimes more than once per week. Family was young then and had lots of fun.

I think I am still within the confines of the intent of this post....talking about props that generate speed that can be measured mounted on OMC engines..........

 

[JimS123]

When they first came out I tried an OMC black teflon SS prop and had one on every new OMC powered boat I bought after that. They were a fine design.

As a teenager my buddy's father owned a Lyman exactly like mine (it took me nearly 50 years to find one for myself). It had a Merc tower-of-power on it but I don't remember the HP. Probably a 30. It took only a minute and a pliers and a cotter pin to change a prop. From his cottage we would run a 2-blade bronze prop (what they called a "speed prop") when we wanted to tool around. When we wanted to water ski we switched to a 3-blade aluminum "power prop". I believe in that era (1950's) the 2-blade bronze was standard.

I don't have a recent Michigan catalog, but they had a full complement of 2,3 and 4 blade props for the Big Twin as late as the 1980's. Maybe their web site shows current offerings. I'm guessing a 2-blade 10 1/2 x 16 on a 14 footer would do the trick for max speed. Also, try AOMCI.org and post a question there. If anybody has a speed bomb Big Twin they certainly reside over there.

Naturally, a tach is needed to be able to dial in a prop. Of course, we knew nothing about those gadgets back then. Als i knew was that dad had a big supply of Texaco 10W30 and the motor ran OK with it.....LOL. That TCW stuff was too expensive and Dad's was free.

 

[jimmbo]

Nice motor, it runs very well, but it's VERY loud and sucks gas like there is no tomorrow....LOL.

In 1955 they made some major changes in suspension mounts, cowl sealing and added an Air Silencer to the carb and really shut them up. I don't think the Fuel Economy Improved much until in 56 on the 30hp when they added the Cruise-Throttle Fuel Saver Linkage, allowing the Carb to be almost closed but the Timing fully advanced

 

[Texasmark]

I had to read your last post twice to reassure myself that I didn't write it. My Western Auto Wizard 25 (based on the Merc Mark 30 design) that I saved up my money to buy at something like $400 back in '57 time line came with the standard Merc styled 2 blade prop.

I too called it my speed prop (yeah right 25 hp SPEED prop) and since it was gutless I bought a 3 blade Michigan bronze and called it my " power prop" (just as you did) thinking it would solve my problems; no access to WOT rpms or any of that stuff as a teenager and I don't remember the pitches of either. Was a waste of my limited money back then. What would have solved the problem would have been to have some more ponies or more cubes supporting the ponies I was supposed to have like my buddies 25 Rude (looked exactly like yours in the picture) on a similar boat that could pull circles around me.

Later on I sold it and bought a new '57 Evinrude 18 Sport twin I think it was called, with the OMC 3 blade alum prop and that 18 did a better job of pulling skis than the Wizard....regardless of which prop I used. Don't remember the particulars on why I bought 18 hp rather than looking for something bigger but that's the way it went. Man those were the days....glad I made it through in one piece. Grin!

 

[JimS123]

I had to read your last post twice to reassure myself that I didn't write it. My Western Auto Wizard 25 (based on the Merc Mark 30 design) that I saved up my money to buy at something like $400 back in '57 time line came with the standard Merc styled 2 blade prop.

Small world, isn't it.

My 1955 Western Auto Wizard Super 10 (Merc Mark 10) cost $229.50. I still have the original manufacturer's catalog, bill of sale and owner's manual. It came with a 3-blade weedless prop. It ran for several years on 10w30.

In later years it became my kicker on 2 different boats. One had a Rude main and the other a Johnny. With each switch I repainted the Wizard to match the main. Still ran strong at 29 years old. Sadly, it went with the old boat when I traded up to an I/O.

 

[roffey]

When I was a boy I had a little 10 foot hydro with a 1957 evinrude 10hp sports twin. I could do about 25 mph and it sure felt like I was flying. My buddy and I built that boat and the one before it. Funny and this will make you guys feel old. When I inherited that motor it was old then and I am no youngster any longer, lol.

 

[Texasmark]

When I was a boy I had a little 10 foot hydro with a 1957 evinrude 10hp sports twin. I could do about 25 mph and it sure felt like I was flying. My buddy and I built that boat and the one before it. Funny and this will make you guys feel old. When I inherited that motor it was old then and I am no youngster any longer, lol.

I can't believe what I am reading. Here's #2 reminding me of my youth. I had an 8' wooden hydro with a Scott Atwater 10, 1955 year model as I recall, 2 blade OEM prop, gold top, green bottom.......had the "Bail-a-matic" system. I had a '47 Chevy p/u that I slid it into to get it to and from the water.....memory fuzzy on this part but I remember I had no trailer.

I too thought I was testing the sound barrier, but in reality probably around the 25 (or less) that you mentioned. In retrospect I think it was because I was so close to the water, thinking about the experience over the years. I do recall that you dare not dump the throttle as the backwash would come over the little wooden stub one might call the transom and put the automatic bailer to work. I do remember it had cable steering and a lockable, squeeze hand throttle...just remembered how that was hooked up.....I think.

Geez,