Logo

1966 Merc 950/1100 crank swap reed valve question

Ctrldinsanity

New member
Hello!

I have a question about reed valves. I'm replacing the crank out of my 66 Merc 950 with an identical crank out of a 67 Merc 1100.

The reed block from the 1100 is exactly same except the reeds and openings are roughly an 1/8th inch bigger all the way around.

As a car guy this equates to slightly more flow, but as a mercury guy I know these motors are like a fine watch and have to be just right.

Will the slightly larger reeds create an issue?

I appreciate your help!
 
If the reed blocks fit the space (ID and OD), then by all means install them. The jetting MIGHT need changing, but I doubt it.

Performance will improve a bit.

Jeff
 
The venturi in the carbs and the exhaust ports designate flow the larger reeds will work just fine they are just valves to control flow direction. Do the 950 mains fit the 1100 crank? Torque the reed blocks to the crank with plastiguage and see if they are within tolerance they are also the main journals. be sure and check end play before you do the final assembly. Put it all together without seals/pistons first and make sure the crank spins free and has the proper end play.
 
Once you put the loctite on the crankcase halves you only have a short amount of time to torque the halves together. I do a couple dry runs then install the seals quickly bolt it together tight. If the crank still has the proper end play your sitting pretty.
 
The venturi in the carbs and the exhaust ports designate flow the larger reeds will work just fine they are just valves to control flow direction

I don't know bout about a 950/1110 model but I do know that if you put 115 reeds in a 90 it wont run worth a chit due to reed stop height. I would check stop height..

If the crank still has the proper end play your sitting pretty.

End play is set before installing front half.....
 
Last edited:
The 950 is a 1000 block with smaller-throated carbs. I don't believe there was any difference in porting. The carb throats are tapered to simulate "velocity stacks".

If you're looking for more performance out of your 95hp, bolt on a set of 100hp carbs.

A '65 100hp uses .065" main jets and the 1100 uses the same size. Both 100hp and 1100 use .1875" reed stops so your performance would be the same as a 100hp.

If you want to retain the original 95hp configuration, swap the 950 reed blocks onto the 1100 crankshaft. Or change the reed stops, which is a bit more work. The reed blocks would be identical except for the stops.

The 950 carbs with .051" main jets restrict the airflow to limit HP. This combined with smaller reed stops (.1562") gives excellent low-end response and good fuel economy. But top end is limited compared to a 100hp.

You may see a slight increase with larger reed stops and using the OE 950 carbs, but I doubt it's gonna be significant and there are larger (optional) main jet sizes if you find it's a tad lean at the top end.

IMHO, I'd slap a set of 100hp carbs on it, use the reed blocks with .1875" stops, and let 'er rip. Your choice.

HTH........ed
 
So far everything is lining up perfectly. I have taken calipers and micrometers to everything first :) The 950 mains fit in the 1100. I'm noticing the only difference between the 950, 1000, 1100 and 1150 are the carb size, reed size and pistons size (excluding igntion type, crossflow type etc.). Confirm end play - check. Thank you so much!


The venturi in the carbs and the exhaust ports designate flow the larger reeds will work just fine they are just valves to control flow direction. Do the 950 mains fit the 1100 crank? Torque the reed blocks to the crank with plastiguage and see if they are within tolerance they are also the main journals. be sure and check end play before you do the final assembly. Put it all together without seals/pistons first and make sure the crank spins free and has the proper end play.
 
That was my concern; do the smaller pistons (~1/4") have enough pull to open the larger reeds all the way/enough? I plan on testing how much weight it takes to open the reeds on both sets and see if there is a difference. I'm noticing the only difference between the 950, 1000, 1100 and 1150 are the carb size, reed size and pistons size (excluding igntion type, crossflow type etc.). Thank you so much!


I don't know bout about a 950/1110 model but I do know that if you put 115 reeds in a 90 it wont run worth a chit due to reed stop height. I would check stop height..



End play is set before installing front half.....
 
Carbs and jets, I really appreciate the info!! I figured the carbs are the flow meters in this case and that the larger reeds shouldn't matter much unless it takes more effort to open them (stiffer reeds). I'm not looking to add performance (yet), doing an overhaul and my current reed blocks are worn a bit at the crank. I purchased a used low hour crank and pistons setup from an 1100. The reeds and openings are definitely larger on the 1100, they are the same opening height but slightly larger openings. All the parts and numbers are the same on the two except the reed/stop and piston sizes. I figured the larger reeds would be OK, but that I would have to tune or replace the carbs for larger and that's what it is sounding like. I'm running .049 jets right now (not sure why) and it's perfect. It sounds like that may have to change if the larger reeds AND carbs are installed. I plan on bolting it up as is without replacing the carbs since i'm not looking for more go (for now), hopefully with a little carb adjustment it will at least run the same as before. Considering what it takes physically and financially to get to those reeds (a 2nd time) I wanted to see if there were any horror stories out there from doing such a thing. I appreciate all the time and info from everyone!!


The 950 is a 1000 block with smaller-throated carbs. I don't believe there was any difference in porting. The carb throats are tapered to simulate "velocity stacks".

If you're looking for more performance out of your 95hp, bolt on a set of 100hp carbs.

A '65 100hp uses .065" main jets and the 1100 uses the same size. Both 100hp and 1100 use .1875" reed stops so your performance would be the same as a 100hp.

If you want to retain the original 95hp configuration, swap the 950 reed blocks onto the 1100 crankshaft. Or change the reed stops, which is a bit more work. The reed blocks would be identical except for the stops.

The 950 carbs with .051" main jets restrict the airflow to limit HP. This combined with smaller reed stops (.1562") gives excellent low-end response and good fuel economy. But top end is limited compared to a 100hp.

You may see a slight increase with larger reed stops and using the OE 950 carbs, but I doubt it's gonna be significant and there are larger (optional) main jet sizes if you find it's a tad lean at the top end.

IMHO, I'd slap a set of 100hp carbs on it, use the reed blocks with .1875" stops, and let 'er rip. Your choice.

HTH........ed
 
The 850, 900, 950, and 1000 are all 90 cubic inches. The difference in HP was mostly from carbs & reed stops. From what I recall, the 100hp had an improved-design exhaust baffle that routed the exhaust pulses more efficiently. My old 850 had the older-style flat stainless baffle plate. When I rebuilt the powerhead I used a 100hp baffle & carbs but I don't recall changing the reed stops. The old Beast ran really strong, though, on a 14' Fiberform v-hulled runabout I got it up to 50 with an old, beat-up 2-bladed aluminum prop. With ski prop a solid 44 mph and would rip a 200-lb slalom skier right out of the water. That was a great motor!

The 99-c.i. 1150 is a completely different Beast and the 90-c.i. motors offer no comparison.

The 1100 was simply a 1000-design block with slightly larger bores for a nice boost in HP. From what I understand they run pretty good, too.

The 99-c.i. 90-hp distributor model had extremely small ports, with really good low-end. But they ran out of steam and didn't do much above 4500. So putting larger reed stops in that motor wouldn't accomplish much.

The first-gen 1150's had Humongous intake & exhaust ports, and Merc choked-down the hp by installing large restrictive venturis in the carb (with smaller main jets to go with), and very skinny reed stops. Conversely, that identical 1150 became a rip-snortin' 1350 with bigger reed stops, smaller, less restrictive carb venturis and fatter main jets. That was a nasty motor and one of my favorites!

Sounds like your engine was originally jetted for altitude and if you're now at sea level, it might run too lean. If you do ever switch to 100hp carbs, they should already have the correct main jets.

If you use the 1100 reed stops/blocks and 950 carbs, be sure to check jetting at full throttle (warm up, go full thottle for a time, then shut the engine down and check plugs). The spark plug insulators should be tan-ish, but if they're bone-white, too lean. Go up to the next jet size in that case.

HTH & Happy Rebuilding.............ed
 
Back
Top