Mercury Mark 40-H

[Mark75H]

Free T-shirt with All Carburettors Ordered

[John (Taylor) Gabrowski]

That is an ineresting new HW carb from Tillotson. It looks like there is less casting and more machining from billet aluminum involved. The HW has quite the venturi which might make one think that the carb being involved in karting has some flexability for both reed valve and piston port motors though much of the velocity stack in terms of what we are doing here might be wasted? Sounds like using the bigger Tillotson HRs sounds good by them too and they do indeed work with their integral pumps and all quite nicely. Sounds like some of this has stirred up some though at Tillotson's home base. To them we are big inch applications they don't see much of and now here is some and it must look wild to them!

[Aeroliner]

Sam,
Looks like I might sell three T shirts to help pay for the carb's.
Alan

[John (Taylor) Gabrowski]

The more I look at these wedge reed block systems with either rounded or squarish reed valve opens and reeds the more complex the engineering behind it gets. Are there any good up to date sights you could recommend to read a lot on internet on the whys, wherefores and reasons for selecting this or that kind of pyramidal reed system for any engine? The only experience I have is limited to Merc standard and modified reed systems for these 4 bangers, combo reed and piston 3rd port systems for Mercs etc. and the kind of work Hubbel did so there is a profound vacumm to read and learn something about. By the look of what your doing you hit the ground running with lots of knowledge already and direction pretty well established. Lots of food for thought in your pictures for anyone else going in this direction.

[nwsteelart@clearwire.net]

thank you for showing those Mercs, Absolutly beautiful ,keep up the great pictures thanks Jim @ n. w. Steel.Art

[Aeroliner]

http://www.sae.org/technical/papers/2004-01-1455

Hi John,
The above link should take you to an SAE website. The site offers you the opportunity to buy software to model reed valves. By the way the reed setup that I'm using comes from a 700 cc snowmobile.

Alan

[A/B Speedliner]

This is a picture of Alan testing his new 1962 Speedliner. In those days we thought we were indistructable, no helmet or life jacket?

[John (Taylor) Gabrowski]

Thanks for the reed valve reed block info. They look high tech and no doubt will work quite well. I was researching operational differences between round tipped round opening reeds systems versus the more squared version in your pictures. Lots of pros and cons but given these are for 444 Merc 44applications using them is going away from the rather intractable reed block systems they have that are wrapped aroung the crankshaft. Going the pyramidal reeds systems to improve the Merc 44s is the only way to go.

The runabouts I ran in stock outboard up to 1983 have the same profile as yours in the picture, a DeSilva type of profile. They were good boats in their day. I took my racing runabout fishing a few times after prop testing, but I still used a bucket on my head. A good habit no matter what seeing what your in.

[Aeroliner]

Hi Sam,
I found my 1975 where used book. If this is what wou would like to scan E mail me at aerolinerboat@aol.com. Looking through it I find it very clean inside.

Alan

[Aeroliner]

Going throught the boxes of things I bought from Harry Brinkman I found a couple intresting "B" crankcase. Anyone ever seen these before? Looks like the reeds were going behind the carbs.

Alan