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Not fast enough!

wired said:
Get a different prop and a tach that works. You should be pushing that motor 5800-6000 . Bad aluminum props will run you in all sorts of circles. If it were mine I'd be running a Solas 19 pitch 4 blade stainless Titan 4. You'll go over 50 with a great holeshot IF your motor isnt having problems..
Click to expand...

Yea I was thinking about doing a 4 blade once i figure out what i need..
 
that speed don't sound right! I would check all firing to plugs! I have a 16ft enticer and with the 115 tower of power it would push the boat 55mph GPS at 5,400rpm bone stock with prop shaft 2in below pad and the enticer is a very heavy boat! I have a mercury 150 on it now and its nothing to run 67mph will run 71mph on a good day! best of luck with your boat.
 
I still do not think the motor is putting out proper power, it should be screaming and over revving the low pitch props. Power packs? Fouled plugs? Carbs leaking? Ignition coils? those motors run so smooth it is really hard to tell by listening. We had a inline 6 ninety on an old Vmate I and ran it a couple of times before we realized we had a bad coil and was running on 5 cylinders.

Good Luck
 
Ok so did some stuff and have more info.. changed to a merc 17px13" prop jack plat is at 5" of setback and prop shaft is 4.5" from pad.. took it out for a run again did not turn up got a tach in it n got it calibrated off a timing light tach could only get about 4500rpms jacked trim up manualy with the stop rod to top just till it was on line of cavitating while driving engine turns 5300rpms now and goes 38-39mph.. still aren't getting that last bit of power and with a 17p prop I'm sure now its gotta be engine related timing is on and carbs are opening fully.. compression was 140 on all last falll ill check it again tomorrow bt is there something I'm missing? Gas was from last fall also but I can't see it effecting it bad enough to cause my issues..
 
Guess ill start pulling plug wires to isolate cylinders.. it runs smooth n turns up good outa water just redid carbs new needles n seats also did fuel pump which was pretty nasty. its got a new timing trigger which I had to do this season and one new power pack I have parts motor here if I do need parts I guess..
 
Stevenlockamy said:
that speed don't sound right! I would check all firing to plugs! I have a 16ft enticer and with the 115 tower of power it would push the boat 55mph GPS at 5,400rpm bone stock with prop shaft 2in below pad and the enticer is a very heavy boat! I have a mercury 150 on it now and its nothing to run 67mph will run 71mph on a good day! best of luck with your boat.
Click to expand...

Enticer is 100+ lbs lighter than mine.. not that heavy..
 
Without motor just hull the sales sheet says 750 mine is 875.

Anyways I found it or at least part of it maybe lol has no spark on cyl 3. Tried swapping coil and wire, wires to coil and power pack.. still nothing. So my question don't the cylinders fire in pairs off the trigger? The resistance check was ok on it when I put it in..
 
About to go find a new motor at this point.. had a bad power pack cdi bought new one now it fires on all cyl. Put 21p back on took it out turned way quicker n felt smooth n faster but was only going around 32mph at 5000rpms. Swapped the 17p back on would still only turn 5000rpms but would go 41mph (finally broke 40mph but doesn't make sence why faster w 17 but turning same rpms??) So anyways was headed back to pull it out n rpms dropped right down would not accelerate at all idles fine just bogs when you give it any fuel.. checked it is firing on all cyl still n has good compression still on all cyl. Frustrated....:brickwall:
 
Well the not going with any throttle was air in the fuel process of elimination came down to the quick connect on engine cowling so just bypassed it seems to be running fine and has no more bubbles of air going through my filter. So back to orignal concern with the 17p prop I can't get it to turn any more than 5000rpms crusing trimmed up before it will cavitate and that's doing 41mph. So I don't really know what else there is besides smaller prop pitch and in that case I'm kinda wondering if this is even a 140 powerhead to begin with.. maybe a 90? Everything says 140 and when I got it I searched all over block to numbers and came up with nothing so was assuming it was.. so now I might have found a 92 140 looper to buy for it instead I don't really like my trim setup I've got going and kinda just want a motor to bolt right back to transom to get my holeshot back... uggh..
 
I thought you couldnt turn more than 5000. Now it wont turn more than 5000 before it "cavitates"? I'm assuming you really mean ventilates. If you are venting the prop you have it trimmed too high
 
Ok no the motor will rev up to like 7k not loaded I just can't get it to turn up loaded.. geez now that I think about it could exhaust be plugged up or something on it? So no matter what under load it won't go past that? That might make more sence why I had no rpm change when going from 21p to 17p although you would think turning the 21p same rpm would make it go faster..

And I ment like when its trimmed up and the prop overturns like cornering when trimmed.. when a prop is slipping in water I've always heard it called cavitation
 
In the outboard context you are ventilating the prop. Air gets sucked into the prop and if its not the right kind of prop for that it spins out of control. Cavitation is a different animal that destroys props over time. If you are ventilating your prop either you are using the wrong prop or you are running it too high for the type of prop it is. There are some crappy props out there that will spin up and not go anywhere no matter what they have stamped on them. What brand of prop are you using?


What do you mean under load? You arent revving it up in neutral like that?
 
What do the plugs look like? Cut the power on one of these test runs while you are at a higher RPM. Pull the plugs out and check them to make sure you are as least burning fuel properly.

Have you checked the spark advance?
 
Ok makes sence on ventilating term. They are both aluminum 13" props ones a merc prop others a michigan prop nothing great.. I still don't see why both props allowed the motor to turn 5000rpms but yet the 21p only made the boat go 30mph while the 17p goes 40mph turning the same rpms...

In neutral it will rev 6000-7000 easy.. under load In water moving can't get past 5k.

I havnt had a chance to pull plugs to check yet just changed them.. I put a new timing trigger in and reset the whole advance I guess I could recheck it while underway running.
 
Dont rev it like that in neutral. You'll kill the motor. It doesnt tell you anything anyway. You could disconnect 4 spark plugs and it would still rev to 7000 in neutral.

If you are only making enough power to push the boat 30 MPH it doesnt matter what prop you are running. It will still go 30 MPH. As far as the prop difference goes it doesnt help you to use a numerically higher pitch if you get outside of your RPM band. There are some Mercury aluminum props ( Michigan too ) that dont even make a good paperweight.

How are you checking your advance?
 
No I realize that just saying in theory it would rev unloaded no problem. Ill try playing with the timing next time I get it out. I set the timing and synced it as instructed in merc shop manual with timing light.
 
If you disconnect the throttle cable at the bell crank and the carbs at the point where the link arm comes over you can fully advance the motor while its running on the muffs without opening the throttle plates. Makes timing it to full advance much more precise. You might run up to 2500-3000 in neutral without opening the throttle plates but your advance will be fully in. Makes setting it with the timing light less of a guessing game where it will end up.
 
Makes sence I never really did understand how they want you to set all the timing while just cranking doesn't really seem like accurate setting. But I guess it all depends on where the throttle lever is in its travel anyways.
 
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