15' Allison 1973

[KEVIN NICHOLS]

I GOT ME A ALLISON TODAY.....I'M GOING TO POWER IT WITH A 150 XS WITH A SPEED MASTER....ANY SUGGESTIONS? I WOULD LIKE TO SEE SOME PICTURES OF SOME ALLISON'S FROM TIS ERA IF ANYBODY CAN POST SOME....... HOW FAST WILL THIS THING BE WITH A 150XS? E-MAIL ME OR LET ME KNOW [email protected] THANKS, KEVIN NICHOLS

[Raceman]

It'll be an easy 75 MPH and a hard 80MPH or more. The speedmaster really helps with stuff like steering torque, but you won't find much top end help from it.

[P man]

love those little allisons
post some pics

[KRAAZYBOAT]

Run the point of gearcase even with the bottom of boat some times you can run it alittle higher but even is a good start. Dave

[CDave]

Go here for Allison pics, http://allisonowners.com/

There are several people over at the Allison Forum with those Lil' Allys. http://pub22.ezboard.com/ballisonownersmessageboard

[Jeff_G]

My opinion, for what it's worth, is unless you are drag racing it forget the speedmaster. For river racin, pleasure or any other use the speedmaster doesn't cut it.

[Bruster]

double teaming with this guy's 1500XS/Allison.

[BHench]

Originally posted by KEVIN NICHOLS
I GOT ME A ALLISON TODAY.....I'M GOING TO POWER IT WITH A 150 XS WITH A SPEED MASTER....ANY SUGGESTIONS? I WOULD LIKE TO SEE SOME PICTURES OF SOME ALLISON'S FROM TIS ERA IF ANYBODY CAN POST SOME....... HOW FAST WILL THIS THING BE WITH A 150XS? E-MAIL ME OR LET ME KNOW [email protected] THANKS, KEVIN NICHOLS

Back in the late 70's-80's I ran an Allison R-16 with a 1500xs. My hull was a 1977, R meaning "race" version.....light layup with center mounted Keller cable/pulley steering. I don't know the exact changes in bottom design between '73 and '77 but they should be fairly similar in terms of speed potential.

Your potential top speed depends on how much time and money you are able/willing to invest in the rig, but 85+mph is not that tough to hit.

First check for any waterlogged flotation, rot, and straightness problems in the bottom and fix all of the above.

Set the boat up with a good center mounted cable/pulley steering system tied to the motors center section (not the steering arm in front). For stability, you need to keep ALL the weight along the centerline (keel) of the hull so don't mount the battery, trim pump, fuel tank, etc back in the rear corners.

Make sure the motor is healthy with good consistent compression across all cylinders. The 1500xs was under rated at 155 hp and 6300 rpm. Mercury had to do it that way to certify the motor for use in JP and SJ classes, which required a "stock" production motor. The term "stock production" motor meant it had to come from the factory with a warranty. Since BIA hp and rpm ratings are for continuous duty, Mercury would have had warranty nightmares if they rated the engine any higher. I was told by the dealer I bought mine from, who was a well known racer himself, that the 1500xs actually put out well over 155hp and should be spun to around 6800 rpm to get max power.

There are two easy mods you can do to get another 10hp out of the motor. Bump the ignition timing about 3 degrees over stock and exhaust relieve the lower unit. Exhaust relieving is done by drilling holes immediately below the cavitation plate on both sides of the rear area of the lower unit where the exhaust flows. Doing this reduces exhaust system back pressure by allowing gases to escape well above the water line when the hull is on plane. Try three or four 1/2 inch holes on each side. Make sure you run 92 octane minimum and if you bump the timing watch for signs of any detonation. Better yet, try and run 95 octane or some booster so you don't have to worry about it.

You should also try and locate a competition power trim unit because the stock system is not stable at the speeds your rig can run......it allows too much movement and just can't lock the motor in position well enough.

I actually kept the top end propeller I ran on my rig. It's a beautiful Mercury 14x30 stainless 2 blade elephant ear, reworked by DAH. With the proper setup this prop will get you 85+ mph. If you've never driven an ultralight 15-16 foot V-bottom at this kind of speed you are in for a great ride. If you're interested in the prop you can email me at [email protected] or call 619-741-6747.

If your motor already has the Speedmaster on it, ignore the above parts about exhaust relieving and the prop. If it doesn't, you might want to try running the stock lower unit with a nosecone and my prop. I never ran a Speedmaster on my rig but I would have to believe you should be knocking hard on the 90mph door with that combo.

Hope this helps you.

Bill

[kim cleckler]

Hey Kevin, see you got that boat sorry i missed you when you picked it up from dad had to carry family to the MNTS> Hurry up and get that thing ready should have the T-2 and 15 ft Kenndy Craft ready in about 4 weeks. Hollow at me Kim Sorry I didnt get that thing pulled up hope it was no problem getting it home!

[Raceman]

Bill, first of all, welcome to Scream and Fly. Second, some of your Ally/1500XS comments seem a little optimistic.

85 MPH in this combo is not impossible, but damn near it. The kilo record for these boats, set up by pros for nothing but top end speed through a measured kilo hovered at 79 point somthing for several years before it was finally bumped.

Exhaust relief has never added a single MPH to any XS I've ever had and I think I have eleven right now, counting the ones in boxes. The only time I'd consider it would be when running a Super Speedmaster which is fairly restricted in the exhaust snout, especially in the later design. As far as the RPM range, there's no question that the guys that are circle racing like to turn em upper 6K's and even more, but for all out top speed, laying the pitch to em and getting them down around 6K flat, or even a little under will always produce a bigger top end number. I ran a 30 on my boat while the circle race guys were running 26's and sometimes even 24's on short courses with one pin turns.

If all out speed is the priority in the 15/16' foot Ally, a very small, almost hard to see hook in the pad, right at the rear, properly designed will add some numbers, but the boats become harder to drive, depending on how fast they are. Paul Allison drew a diagram for me about 25 years ago. As far as I know, the newest DR Allisons still don't have a dead straight pad............ my 96 model didn't.

All the 1500's are extremely prone to detonating a piston, and it's a hard thing to detect before it's too late. Bumping the timing past 21º is asking for trouble. The higher timing actually does more for acceleration than top end numbers anyhow.

As far as the Speedmasters, I've run em for years on all my stuff and particularly like them. In a 1500XS/Ally combination there's probably no speed advantage, or at best a very small one, given today's availability of props for the larger units. The big advantage in the Speedmaster is in the total lack of steering torque and improved handling. I do differ on Jeff's opinion of the use for lake and drag boats. Most people prefer not to run the Speedmasters on drag boats unless they're rope racing because the acceleration is extremely poor, especially from a mush/idle speed like the ODBA uses. I particularly like the Speedmaster's manners for a lake boat with the improved handling, but of course the lack of neutral and reverse is an inconvenience at times.

I'll stick by my original comment: 75 MPH is an easy goal with one of these combinations, 80 is tougher, 85+, I don't see it happening, at least not for the average guy.

[Dave S]

Raceman you rite about the SSM and streering. The big 2 blades a blade slingers and prop shaft snapers. But for that extra 5 MPH you gotta give it that 27 BTDC and the Tunner, Tuner Tuna. ;) I was told back when that the 155 HP was because of the lovered cowl. Naaaa:p I would not doubt B Hench he seems to have dun it.

[BHench]

Raceman and Dave S,

Thanks for your comments.....This is a cool website and I'm starting to think if I hang out here long enough I'll be looking for my next boat, after being dry docked for a while.

I can only tell you that the R-16 I had did pick up a couple of mph after it spent the better part of a month upside down in my garage getting a meticulous blueprint job and some very expensive linear polyurethane paint. I even "blueprinted" the lower unit by smoothing, sharpening, thinning and deburring its various surfaces. I had no choice in doing the bottom after my dufus brother "parked" the boat up on shore for me one time.

As far as the actual top speed I have to say it was long before GPS was available to the public, so the absolute number is unknown. What I can tell you is I did see 6800rpm while turning a 30 inch pitch prop. That gives a theoretical speed without slip of 96.6mph (3400x30/1056). I also had a Land & Sea Medallion speedo that danced in the 85-86 range in perfect conditions. Those numbers would indicate about 12% slip if they are both accurate and the prop had a true 30 inches of pitch.

Certainly the possibiliy exists that the instruments were not spot on. I still believe I did an honest 85+ because I worked very hard to achieve an above average setup with meticulous attention to detail. Hell, my girlfriend back then always complained the boat got much more of my attention than she did....and she was right.

What surprized me most about your comments is the one about rpm range for the 1500xs. That's the first I heard of running that engine down so low for top speed. My Mercury dealer said 6800. When I picked up the boat at the factory I talked with Darris, who was a big fan of the 1500xs back then, and he told me to prop the motor for at least 6500 or I would not get the full horsepower out of it. You will usually feel a motors power fade when revving it past the power peak but I recall the xs still pulling/accelerating hard well past 6k.

Any readers out there ever run a 1500xs on a dyno or seen a dyno run chart showing horsepower and torque curves?

Raceman you mentioned you have eleven 1500xs's including the ones in boxes.........are the ones in boxes by any chance "new old stock" motors you stashed away??? If so, how about selling me one......then again maybe I should start thinking more new school, like a 200xs for my next rig.

Bill

[Raceman]

"I was told back when that the 155 HP was because of the lovered cowl. Naaaa"

The 1500XS had higher port timing, which it shared with the T2, 650XS, & 700X according to the APBA spec sheet. (at least as far as the exhaust port height goes) It was also jetted differently and had a different part numbered switchbox. For whatever reason, Merc elected not to raise the ports to this same level in the 850XS, leaving the powerhead exactly the same as the std 850. The fact that the height on the more radical race engines wasn't carried higher has always been exactly partially responsible for my opinions that raising the port timing on a 1500XS is not helpful at best, and probably even counter productive. This is also coupled with the fact that I had one done by Quincey Welding (scratch engine and component builder extraudinare') and although the motor lost some on the bottom, it didn't seem to gain on top.

My first Ally was a 15 that was a competitive APBA race boat and a couple of years old. It originally had a 73 shortshaft 1500, and when I bought the XS powerhead and stuck in it, I remember being disappointed in the lack of substantial increase.

When I first started foolin' with my boat, my interest was in Kilo records. For several years the JP record hovered just under 80 MPH and the JS right around 90 flat, give or take. I remember that David Lee and Doug Pearl both got their JS boats up around a hundred in Kilo trim before the class died, but there was a lot of chatter and speculation about how it happened, ranging from majic powerheads from Merc to crazy surveying on the course. I've always believed the speeds were legit probably, and the increases came at least partially from the improvements in the cleaver technology and resulting extremely high transom heights.

The only thing I can say for sure was that I never got my 15' boat with the J (XS) powerhead to run 80, and there were several pretty smart people helpin' with it.

My memory of exact RPM is fogged partially just because I have a foggy memory, and partially because I made the transition to Speedmasters on the little boat, but I'm real certain that the 30 pitch wheel was several MPH faster than the 28 on my boat, and when I changed to the 1:1 SSM the 16 ran faster than the 15 I tried and still at a lower RPM than the 30 had turned on a larger gearcase.

The motors that I have in boxes are just stuff I've accumulated and disassembled for various reasons. The only NOS stuff I have is a pair of bare blocks that I bought off the For Sale Forums here several years ago.

It's a shame that Merc doesn't still sell the 1500XS and Allison doesn't still build the boats. It's a great combination and I think one that would be popular still.

[Raceman]

This is the only one I have that's currently running. I ride in it more than the other stuff because it's such a fun boat. The bottom's never been done on it. I don't know anything about the race history on it, but it was lettered and numbered before I bought it.

[BHench]

Thanks for the picture......now I want my old R-16 back even more! Mine was the same color combination as your hull.

I bought my motor just as Mercury ended production on the 1500xs. Last year was '78 and in Jan. '79 I paid $2600 for a new motor in the crate. Mercury was discounting them cause they didn't want to get stuck with too many leftovers. Today a 25hp electric start lists for more than that!

The thought never occured to me back then that I had an exceptionally fast R-16 Ally, but apparently I did. I live in San Diego California and there were no other Allisons around to race back then. All the west coast hulls with 100 cu. inch motors were not even close to the performance level of the Allison. I would even get by 99% of the V-6 powered rigs I ran against. It's regretable I never had the notion to do a kilo run.

When it came to handling the Ally was a dream to drive, carving around corners like it was running on tracks. It amazed me many a time when I would be running 70 or more and misjudge a wave, only to find the boat would cleanly cut it's way through with little more than a thud. Sweeeeet!

[race#115]

i had the r16 as well white and red with the x1500 on it and a 30p and it would go over 80 no problem but at first they are a handfull to drive .when the merc went i put a 110 vro on it i remember the prop but it still did 70+ the boat was alot of fun and i still know where it is i should go buy it back.