WOT for alpha one

[wilvn70]

I don't know how to title this, but I would like to know what ratio of alpha drive I should use to give me the best prop rpm for an 3700 rpm engine range.
I am running a 1951 Flathead Mercury 254 cu inch of about 130 Hp.
I do not want to over rev it past 4000 rpm.
It is being installed in a 16' Marlin. Looks like a ski or drag boat with wide beam and no windshield.
Any input will be appreciated so I may be ahead on the trial and error stage of it all.

Thanks,

Will C

 

[Bt Doctur]

Re: WOT for alpha one

Thinking the 1.98 ratio would work for that hp.

 

[alldodge]

Re: WOT for alpha one

I don't know how to title this, but I would like to know what ratio of alpha drive I should use to give me the best prop rpm for an 3700 rpm engine range.
I am running a 1951 Flathead Mercury 254 cu inch of about 130 Hp.
I do not want to over rev it past 4000 rpm.
It is being installed in a 16' Marlin. Looks like a ski or drag boat with wide beam and no windshield.
Any input will be appreciated so I may be ahead on the trial and error stage of it all.

Thanks,

Will C

:welcome: to iboats Will

I'm not familiar with the flathead Merc WOT. With that, appears you need to know what is the correct prop needed for your boat. In order to attempt to answer the question we would need to understand what you have.

Is the max WOT 4000
Weight of the boat with gear and people aboard
I also would suggest the 1:98 without knowing the rest of what you have

 

[wilvn70]

Re: WOT for alpha one

Thanks for your response.
I was thinking the same thing, but have not had any experience with the drives.
The engine is a flathead V8 1951 Ford and it will be a 2/3 passenger boat.
My concern is the rpm, The hp is at 3700 rpm but max tq is about 2200 rpm.
I don't want to over rev it.
The 16' boat is fiberglass and had a merc 90 outboard on it when I got it. I have no idea what the weight will be.
I am converting it to the flathead i/o to play with and pull behind my '51 flathead Merc powered '29 Ford coupe.
It may not be the fastest boat, but it will sound nice with the up swept pipes I have on it. Pluse I think rather cute.


I think the prop will be the way to adjust the RPM.
I just have never had any experience in trying to do this before and wanted some input to help.
I did get an outdrive with the 1.98 ratio as I was going by the horse power of the engine as a guide.

Thanks for your help.

 

[alldodge]

Re: WOT for alpha one

Thanks for your response.
I was thinking the same thing, but have not had any experience with the drives.
The engine is a flathead V8 1951 Ford and it will be a 2/3 passenger boat.
My concern is the rpm, The hp is at 3700 rpm but max tq is about 2200 rpm.
I don't want to over rev it.
The 16' boat is fiberglass and had a merc 90 outboard on it when I got it. I have no idea what the weight will be.
I am converting it to the flathead i/o to play with and pull behind my '51 flathead Merc powered '29 Ford coupe.
It may not be the fastest boat, but it will sound nice with the up swept pipes I have on it. Pluse I think rather cute.
View attachment 225793

I think the prop will be the way to adjust the RPM.
I just have never had any experience in trying to do this before and wanted some input to help.
I did get an outdrive with the 1.98 ratio as I was going by the horse power of the engine as a guide.

Thanks for your help.

When I first looked up your boat I couldn't find one with an I/O, so your going to make the first one, maybe. Your going to add a lot more weight to the boat. Why a flat head Ford, why not a 3.0L?

 

[wilvn70]

Re: WOT for alpha one

I am building it for a unique play and show toy.
I am into old model 'A' fords with flathead engines installed. "Nifty Fifties"
I think a small boat like the Marlin would make a great vintage looking racing/drag/ski boat.
I have a set of upswept exhausts and would never put them on a car. But in the back of an open boat like I am doing, I think it will make it a rather interesting conversation toy.
My Dad (in the 50s) had an old molded hull 12' with a Johnson 22hp 2 clyinder opposed and it always created a conversation and sounded so neat.
Flathead fords always have a very distinct sound and I think it will be fun to play with and show.
I am retired and always looking for something different to build.

I like the shape and size of the Marlin. I think it deserves an I/O setup.
Besides, anyone can go buy a 3.0 powered boat.

Will C
Just killing time before it kills me.

 

[MikDee]

Re: WOT for alpha one

I had an 18' Higgins plywood speedboat, that had a 135hp graymarine engine back in the day. It was running a direct drive 12"x 12" Prop. and did 38mph at 4000rpm. I don't know how to pick a prop for you, but thought this might help some, as it had 135hp, and an average 16'boat with a Merc 130hp I/O and 1:98 gearing uses a 13"x 19" prop. Maybe you can find a marina, or boat store to lend you a new, or used prop so that you can dial your boat in. An old flathead huh? I'm a fan of yours Good Luck, Mike D.

 

[wilvn70]

Re: WOT for alpha one

Thanks, Looks like I may have lucked out. I will have to check, but I got two props as a part of the deal for the outdrive.
One was stainless and the other aluminum. Seems that one of them was a 19 and the other was about the same. I will not be home to PA for a couple months but will be mounting the engine and making an adaptor right after I get there. I am sure one of them will be good for a starter to check things out with. Only other problem will be should I leave the water pumps on the engine or just depend on the one in the drive.
Any Ideas on this? Will C

 

[alldodge]

Re: WOT for alpha one

I am building it for a unique play and show toy.
I am into old model 'A' fords with flathead engines installed. "Nifty Fifties"
I think a small boat like the Marlin would make a great vintage looking racing/drag/ski boat.
I have a set of upswept exhausts and would never put them on a car. But in the back of an open boat like I am doing, I think it will make it a rather interesting conversation toy.
My Dad (in the 50s) had an old molded hull 12' with a Johnson 22hp 2 clyinder opposed and it always created a conversation and sounded so neat.
Flathead fords always have a very distinct sound and I think it will be fun to play with and show.
I am retired and always looking for something different to build.
View attachment 225869
I like the shape and size of the Marlin. I think it deserves an I/O setup.
Besides, anyone can go buy a 3.0 powered boat.

Will C
Just killing time before it kills me.

I like it, and I use "He who dies with the most worn out toys wins"

 

[Maclin]

Re: WOT for alpha one

The cooling system will be the next challenge. The spent cooling water on almost all recreational boats exits with the exhaust, main reason is to keep the exhaust cooler inside the boat and also the most logical for exiting. I would research marine exhaust with open headers to get an idea of what will work with what you are trying to do.

Not sure if that vintage of flathead had a marinized version used in an inboard boat back in their day, but if so that would ne the place to start for cooling system components and plumbing arrangement.

Good luck on this project.

An idea keeps popping into my head, making the engine house look like a (oversized) flathead and maybe even have zoomie fakes popping out. That way it would not really matter what was under the hood so to speak.

 

[wilvn70]

Re: WOT for alpha one

Well after researching the net more for open exhaust engines, it seems just pumping the hot water back through the outdrive will do no damage. Using a pressure fitting instead of the exhaust bellows, any reverse water flow will not happen and I will never have to replace the exhaust bellows. The nice thing is I can use the standard flathead water pumps as they are also the motor mounts.
By the way, there will be no covers aft of the seats. I don't want to cover up the Flathead Merc. Marlin did make some small I/O boats about this size called the 'Scorpion'.

Thanks for all your help, I will post some pictures once I get started in May. Will C --- Chiang Rai, Thailand

 

[MikDee]

Re: WOT for alpha one

IMO, why not go for a jet drive? Or, a Vee Drive, They are a lot lighter, & more compact. You're putting a lot of weight, & complications on the back of that low, light 16ft boat. Besides, jets can usually get away with running open pipes. You do know that you need the whole transom assembly for a Merc I/O, with the built in "floating" rear motor mounts for driveshaft alignment, and possibly a custom made motor coupler to bolt to your flywheel, and, match up plus fit up with the outdrive splined shaft. Plus, you'll probably need the whole power steering set up with the hydraulic piston, reservoir and oil cooler. Of course you'll need the complete power tilt, & trim assembly with it's reservoir, and the shift interrupter assembly, plus the Merc. controls. By the way, where are you mounting your fuel tank? One more thing I/O's all use a 140 degree thermostat.

 

[midcarolina]

Re: WOT for alpha one

From your earlier posts it seems you are concerned about the cool factor of this boat..... I would be too! it's gonna be very cool...

But since that is an important aspect of the build I agree with MikDee......... I would bo looking at an older vee drive.... to me that adds to the flathead cool factor. Do a quick google image search for vee drive there are lots of pics of boats sorta like yours with vee drives, from mild to crazy wild...

 

[MikDee]

Re: WOT for alpha one

Some important facts you need to know:

All inboard, & I/O boats come equipped with mandatory Coast Guard approved exhaust air blowers built in under the gunwales to exhaust the air in the bilge in case of gasoline leaks, and, or fumes, to prevent explosions,,, they are required to be run for 5 minutes before engine startup! But, can also be run all the time if desired. They are powered "scuppers". You must install these. A fire extinguisher, and a whistle or horn are also required.

 

[midcarolina]

Re: WOT for alpha one

I was thinkin he would have the engine open to atmosphere with NO enclosure....like a old speed boat, in that case the blowers are not required..

 

[achris]

Re: WOT for alpha one

I suspect that engine puts out quite a bit of torque, so the horsepower becomes a bit irrelevant. For that reason I would go to a lower reduction ratio, and since it's in such a (relatively) small boat, same thought. I would look more at a 1.65:1 drive.... Then change the prop pitch to tune in the right revs.

JMHO

Chris.....

 

[MikDee]

Re: WOT for alpha one

I was kinda thinking that myself Achris, I just never put it out there, but you maybe right?

 

[Walt T]

Re: WOT for alpha one

I for one would really like to see this. I'm gonna bug Will C to post pictures but... we'll see.

 

[MikDee]

Re: WOT for alpha one

Thinking about it, having 130hp @ 4,000rpm, then he probably has the right outdrive gearing, and probably the right pitch prop at 19" pitch, or possibly a 21" pitch prop, one of these should dial it right in.

I'm a big fan of this myself!

 

[wilvn70]

Re: WOT for alpha one

I do have a Berkeley jet drive on a 21 foot with a 454cu inch(7.4 liter) Mercruiser engine.
I don?t want to tear it all apart just yet as it is a very nice boat, just no paperwork as it was abandoned on my property quite a few years ago when a renter left in the middle of the night leaving me with rent due.
I have everything to hook up to my engine and it seems all I will have to do is drill holes to match the flathead. My bolt circle comes out in the flat area of the flywheel surround and will be easy to do once I get it in proper position. The length seems to be almost identical.
The boat had a very heavy 90 hp Mercruiser outboard hanging on the back with all the cables for shifting and throttle installed with a steering wheel and all gauges including a tachometer. It has the power trim controls and I have a complete trim system.
I am looking at using a triangle shaped coupler to mount on my flywheel.
The fuel tank is mounted under the deck in the front. I am sure I will have to clean it.
Why power steering?
My flathead runs best at about 180 degrees. Is there any reason I have to worry about the standard 140 degree thermostat? The water passing through my water manifold will be tempered a lot lower by the amount of water passing through the manifold as shown in my sketch. The engine will be controlled by the thermostats, but with that much water going through the system, it should be quite cool other than inside the engine. By my research, it seems the engine will use a lot less water than the Alpha drive will furnish so there will be a lot of flow through the water manifold and the engine will just use as much as needed. The rest will just go through the water manifold and dump back to the Alpha drive.
Hmmm! 1.65:1 would that spin the prop faster for lower engine rpm?
The max torque of the engine is about 1800 rpm. That is one of the characteristics of Flatheads.
I am sure once I try it with what I have for gearing I will be able to tell right away and change just the gears if needed.

I am sure to get the coast guard involved for all safety features I will need. This will be an all open boat with no enclosure aft of any sort. We will have to see what they say.


Will C