1982 tower of power timing questions

[Mybiggles]

I would think a 17 is what you are going to need, I used a 19" on a 15ft boat(850lbs for the boat) and it hit 5500 rpm

was that a 13" diameter? what brand of prop was it? I just ordered a turning point hustler 17 pitch from amazon. ill see how it goes. good thing about amazon is I can always return it lol

 

[jimmbo]

Mercury props both AL and SS. That was back in 1985 thru 97

 

[Mybiggles]

Just took off the stock prop which was a black max 13x19. No idea of the revs or how the damage was affecting it but thinking the 13.25x17 prop I grabbed was a good choice

 

[jimmbo]

Check over that Hustler carefully. Run your hand over the blades and check if all of the blades feel like they have the same contour. I have seen many TP props with one Blade of the 3 having a different contour.

 

[Mybiggles]

The prop felt pretty uniform but it's hard to tell by hand. However when installed and turning it 1 of the 3 blades would catch on my anode. Not sure if the prop shaft has a slight bend or if it's the prop but it is what it is, at any rate it's significantly better then the old prop. I'll try it out on the river hopefully this week and go from there. I kinda want to try a 4 blade hustler so I'll probably change it out anyways.

I also finished rewiring everything today. It's now upgraded to blade fuses and everything works as it should. Does anyone know what kind of amperage the stator puts out? Is the upgrades to it? I'm wanting to install a stereo and I'm wondering what kind of power I have to work with.

The carb kits should arrive tomorrow. I watched a rebuild video that talks about disabling the economiser learn burn thingy. What's the best way to do that? Should I just replace the hose with 2 caps or do I need to modify anything else?

 

[jimmbo]

Those unregulated charging systems put out about 6 amps

"Economizer lean Burn thingy"... I will assume you are referring to the Back Drag feature of the Carb(worked OK in the 70s when Gasoline was Gasoline, not the Alcohol laced garbage that smells like Cheap Cologne being pawned off as Gas these days). All you have to do is remove the hose from the fitting on the fuel bowl, get a small ball bearing(bigger than the inside of the hose) and shove it into the hose and then put the hose back on the fitting. Alternately, you can place a cap on the fitting on the carb throat, instead. The fitting on the fuel bowl can be left open.

To see if the prop shaft is bent, take the prop off, With water supplied by muffs, run the engine, shift it into gear, on the end of the propshaft is a cone shaped depression, Get a sharp pencil and place it in that depression, you will know if the shaft is wobbly or not. If it is bent, it will lead to vibrations that will damage your engine, gearcase, mounting/swivel brackets, plus be noticeable in the boat. Some people claim they can straighten a bent shaft, I say they are full of brown stuff

 

[Chris1956]

I doubt you want to run a 4 blade prop on a speedboat. 4 blade props are generally used for heavy slow boats.

The TP hustlers are pretty good props for speed boats, but in the 3 blade version....

 

[Mybiggles]

Thanks again for the advice jimmbo

As for 3 vs 4 blade turning point and most reviews of the 4 blades I've read only list like a 1-3mph drop in top speed but a pretty huge improvement in hole shot, handling and plaining. It is a "speed boat", but it's not very fast lol. It's around 2000lbs with gear and 2 adults. With the damaged prop it was only doing mid to high 30s, I'm hoping with a better prop it'll do 40-45. Id rather sacrifice a bit off the top of everything else is improved. I'm getting the props from amazon so they are "free" to try lol

 

[jimmbo]

I doubt you want to run a 4 blade prop on a speedboat. 4 blade props are generally used for heavy slow boats./QUOTE]


Careful with that statement. Myself, I HATE 4 blade props, but they have been seen on Offshore racing hulls and and they aren't slow.
I would really like to see Mercury return to making 2 blade props, to use on their I/Os

 

[Chris1956]

Jimmbo, he is talking about a 4 blade alum Hustler, not a 4 blade SS chopper/cleaver used in off shore racing. I am trying to help steer him away from turning that thoroughbred into a plow horse.

 

[Mybiggles]

Jimmbo, he is talking about a 4 blade alum Hustler, not a 4 blade SS chopper/cleaver used in off shore racing. I am trying to help steer him away from turning that thoroughbred into a plow horse.

at 35mph its hardly a thoroughbred, despite how fast it looks like it would go lol.

New carb kits cam in last night. pulled the carbs off today and im going to rebuild them and throw them back on tomorrow. man that one nut on each carb is tricky to get at, I had to pull the caps off the float bowls to get at them. in hindsight pulling the starter off may have made It a bit easier?

I also noticed the lock nut for one of the timing screws was loose so who knows what its at. once its back together ill have a go at trying to time it properly. I did notice on the motor it said to set max spark advance at I think 20 or 21 degrees, weren't these originally set for 23 degrees and once ethanol came along it got dropped to 20 or 21?. what should I be shooting for max advance? 21?

 

[jimmbo]

35mph, at that speed even a 17 is probably too much pitch

 

[Chris1956]

Taking the starter off makes removing the carbs easier. Also, ditto taking the carb bowl covers.

Max spark advance s/b 21*BTDC. Make sure the carbs are synced to the idle pickup timing spec. Check compression and spark to make sure she has fire and power on all 6.

I would hope you can tune her to pull pretty well and still get to 35+MPH. My 16 footer with an IL6 would hit 55+, but the boat was only 700# and pretty flat bottomed.

 

[Mybiggles]

35mph was like the average speed with the old damaged 19 pitch prop. Still haven't had a chance to take it out with the new 17 pitch. I had it around 42mph once with the old prop so I'm hoping I can get mid to high 40s from it when it's all dialed in.

It's definitely running on all cylinders. Despite leaking tons of fuel out of the carbs and loosing prime it ran very well as is. Would always start easy and never really bogged down or anything that seemed out of the ordinary. I checked compression a few months back with an old gauge that I'm not confident is super accurate but all the cylinders were right around 120psi. What's ideal compression on these things?

What do you mean synced to the idle pickup spec? Are you talking about the butterfly adjustments to all be lined up properly and idle timing set for a smooth idle? I wish someone would make a video on how to time these motors with the coil packs. Most of the information and guides I find are all related to the older distributor style. Regardless I've read through the guides for setting the carbs and timing a few times but will have another go at them before I attempt to mess with it.

 

[jimmbo]

There is no Idle Timing spec on these engines Period. The spec for the the Pickup Timing, can and does vary depending on engine model and serial #. In your case you have chosen 6*. The poster who said 'Idle Pickup Spec' may have been pointing out it was at a speed closer to idle than the max timing advance spec.

One thing a lot of people don't understand, or can't, is that all the spark advance will occur with very little movement of the carb butterflies. Once all the advance is in, the carbs will really open. This allows the engine, when running at high speed, to permit the carbs to close greatly while retaining full spark advance. The result is a slight drop in Engine RPM, with a substantial drop in fuel consumption.

Mercury has never listed a specific # for compression. They have always said within 15% of each other. On these boards some people have claimed 150+ readings, I doubt numbers that high, as these engine don't have high enough compression ratios to deliver them.

 

[Mybiggles]

from my understanding the "base" timing range is just to set the proper idle speed with the butterflys closed. Is the point where the spark advance kicks in adjustable or is that something that's just always right?

I didn't get much time on the boat today. I got one of the carbs cleaned and reassembled. For the float spec the paper listed something like 13/32 between the cap seat and the top of the arm, the 2nd spec it listed as .04" clearance between a bottomed out pin and the levers hanging upside down. I wasn't quite sure how to exactly measure that. I did find a video on youtube that suggested a 1/4" gap between the 2 arms when hanging upside down is proper and that's what I set it up. I don't have a precise ruler so im using a measuring tape with 1/16 graduations and I think I got it pretty close to. is that 1/4" gap good enough or should I find a way to measure the .04" clearance?

 

[jimmbo]

Myself, I would look at the Base Timing spec as the Max Advance, the Pickup timing as the point where the carbs are just about to move off the fully closed position as the timing is advancing, and the idle timing is whatever it needs to be to attain 600 - 650 in gear on the boat

 

[Mybiggles]

Myself, I would look at the Base Timing spec as the Max Advance, the Pickup timing as the point where the carbs are just about to move off the fully closed position as the timing is advancing, and the idle timing is whatever it needs to be to attain 600 - 650 in gear on the boat

so how is this all adjusted then? I'll have to look through the guides again, but from looking at my motor just above the carbs on the right corner of the motor there is like a red plastic block thing with 2 set screws and a couple of rods that head towards the rear of the motor under the "timing" covers. Are these idle and max advance adjustments? if so where does the pickup timing come into play and how would that be adjusted? sorry for my ignorance, I really should get a shop manual lol. if anyone has a manual for the coil pack motors and wouldn't mind emailing me the pages related to setting the carbs and timing I would really appreciate it.

 

[jimmbo]

Here is a video where the guy does a decent job explaining which screw/bolt does what. I take some of the other things said with a grain of salt.

https://www.youtube.com/watch?v=AEbx3R5lZNI

 

[Mybiggles]

thanks so much that guys videos are awesome! In his video about the link and sync for the carbs, he says to have it in the water in forward gear. would having the leg in a bucket of water work as well or should it be in a lake?