Finally GPS'd the speed on the 75 MA
 

Had to download a ap to my android to get a idea on how fast the old MA ran... 1975 MA 35 gals (3/4 tank) fuel 2 guys 1983 115 mariner. 5800 rpm on the tower of power in line 6 produced 40 MPH... WOW !!!! didnt want to push it any harder and had throttle left.. i may have to try this again with more crew on the boat to determin if i need to get a bigger prop... swinging a 14x17 3 blade currently... i can not beleive the boat hit 40 with the old 115... looking at a possible trade to a 150 EFI mariner though.. My hats off to Mr Carl and his flying machines and Mr Bill for buying it and mass producing !!!! looked at the numbers and i have 1 of 23 MA's built in 75 and 1 of 327 total... if it was a similar car it would be VERY expensive... we are very lucky to have these jewels !!

Rusty,
Excellent numbers. I was told these motors could be run into the 9ks rpm by gifted folks, achieving tremendous power and torque. Trick was get past the motor's own self-destructing harmonics around 6700rpm, iirc.

I'm running the '83 Merc model on a Seafari and getting 36mph (mounted external antenna gps) @ 5500 rpm with a 13-3/4 x 15 Merc Black Max w/ anti cav at 1-1/2" above keel. Very curious as to what prop brand model etc you are using, and how high your anti-cavitation plate is relative to your keel at parallel trim.

Nice to hear your story.:cool:

Just came across a really clean 150 I-6 and dang, it's tempting, but next motor will be modern with eye on mpg and expanded range and relative silence.... Can you say E-TECH? sure... ah knew ya could...:D

i hear ya on the E tech !!!! What is the max RPM i should consider turning... i ran my black max to 6000 + all the time. I was REALLY considering working the old I6 just to stay nostalgic and keep the Classic look.... and may shelve this motor for a later project... that being said i would need a MUCH larger fuel cell for me to take my boat where i eventually want to run it to.. the plan is to rig this boat for 200 mile round trip runs ( we do this on a friends 18 McKee )... I also hope to make a bahammas trip on this one next year.. i Started that dream as a kid after my uncle returned from walkers caye and told me about running over there.. i bought my 23 Sceptre with that intention then LIFE pulled a few pranks on me... when i get home we will be using the boat alot due to snapper season and sunshine i will try to get some numbers and measurements for you... the prop looks to be very old school with a larger blade with less rake than i am used to seeing on my bass props.

Egg a Muffin.

"then LIFE pulled a few pranks on me... "

YOU too??? Damn, I thought it was just me! :) :) "Life", that tricky little bastard!!

We moved to a much less affordable nome then my wife lost her job and i took a cut in pay ... the total of the 2 LIFE pranks was over half our annual income... my wife was making more than me :)... almost lost the house... gave the bank the keys to a truck ... BUT... we were able to modify our morgage... twice... Keep the house.. and save a lot we paid cash for after selling our first house.. looked at bankruptcy but after talking to a lawyer decided to go at it on our own... Later hired a lawer friend to help out and our last LIFE lesson will be behind us soon... It all worked out in the end as i have a better job. My wife started a business and moved on to another field of work and should be out earning me again shortly... ( she's the brains of the family ) and in 1 year my youngest daughter will graduate from high school without her mother and i loosing our marbles... ALL this and i have MY/OUR beloved running SeaCraft.... LIFE has thrown it at us and we just keep bobbing and weaving....

sure, I like the way you say that...:cool:

Just keep slippin those punches Rusty...the rop-a-dope is over-rated... too many body shots...
Hang in there and best of luck going forward!

Thanks !!! The worst is behind us i think... even looking at maybe finding one of the total refit project 20's for me and my daughter's to rebuild... i love the one on here that was turned into a reardeck bay skiff... add a trolling motor to the front and it is almost ideal for trout around here... i have a donar bassboat that i could rob from and then ditch the hull...

Wimpy, wambly, wombly.

Endeavour to perservere.

I am running an '86 inline 115 merc with a 13.25x21" Laser II. Max im getting with a half tank and 2 people is 46@ 5800. Torque is unreal, with myself and about a 1/4 tank of gas it's 48. motor is mounted on the 2nd hold, and cruises right around 30-32 @ 4-4200 depending on load.

This is a very curious situation.:eek:.
Normally I'd call bullshit but I know these motors can be wound up and spit fire. But 5800 rpm, ain't exactly wound up.
All sorts of questions but let start with this one:
What boat is this on?

And then we declare war, right?

its on a '72 20' cc. before I say anything else. I pulled it off a bass boat, and I have no idea if the guy before me jetted the carbs or not. I just know that I'm turning a 21" laser ii @ 58-5900 consistantly and getting 47 mph. I've only seen the 48 once, and it was with a slight chop, and a tail wind.

Roger that, povertysucks.
I would be interested in learning more. I was expecting you say it was on a bass boat, but I knew you had a 20 cc. Your numbers sound a lot closer to a 140 or 150 model. Can't help but wonder if the carbs weren't the only thing altered. 150 power head? 115 cowling, FL sleeper?

I have a healthy '83 115 and am pretty sure it won't even turn that prop. Heck, I'm running a easy to turn 15 p just to get 5600 rpm.

How high does your bow run and do you use trim tabs to level her out. I know the Laser II is a great speed prop but I'm very surprised you can spin any 21p on this hull with said motor at 2:1 gear ratio.

How high above the keel is your anti-cavitation plate?

Thanks for any insight you can offer.

Lol, florida sleeper, that's awesome. I dont think it is, the serial numbers say its a 115. I have no trim tabs on my boat, and it's about even with the keel. I might even be able to mount it one notch higher. I can tell you that offers a hell of alot of both bow, and stern lift. It shoots a nice tail when hooked up. I have some pictures of me doing so too. It hauls the mail for sure.

The first picture is before I swapped out the motor. the blue band was an '83, and I was getting identical #'s as McGillicudy

Second picture is me testing the 21' Laser ii with the '86 115.

Last picture is the motor I currently have. I am NOT running the Doelfin

Looking super light. And fast! Better get yourself together, er, I mean, better get yourself a tether... Still got me wonderin' where you're getting the extra 10 mph...

Awesome.

Can you post a couple of pictures of the carburetor setup you have on that 115?
I'd be interested in seeing if the carbs are WMK 14's off a 140/150 I6 Merc. It may well be that you've got the 140 powerhead "Florida Sleeper". I've done that trick twice.

I used to run an '83 140 powerhead on an '81 115 mid-section. I used all the externals from the 115, as it was on the back of a 15' Cacci Craft copy of the V-Mate, and the boat was labeled "Max HP: 115".

I could just touch 85 mph with a 2-blade 32" pitch over-hub solid brass prop at about 6300 rpms. I'll never forget the day it threw the #2 rod out the front of the motor and right through the center of the dash. I think it was several minutes before I really comprehended what had almost happened.

You guys are getting me excited about these old Mercs. If my 90 ever takes a dump I might have to find me one of those.

Fr. Frank that is a gnarly story about throwing a rod. Someone was looking out for you that day.

they are out there and there are still some people around that know the tricks to tweak them... my dad ran 136 in the straits and 90 in the turns wuth a 140 massaged on a sst 140 back in the 80's....