Efficiency increases

[hbryant123]

with two people in the boat my 1974 105 will push the 16.5 foot boat to about 42 mph with a 13x19 prop, This year i am going to re-synchronize the carbs and timing. I also had read about switching lower ends for more efficiency, which lower end is this that will fit? Also on my distributor there is like a small fine tune adjustment i was wondering how to adjust this? thanks in advance

 

[Frank Acampora]

Re: Efficiency increases

At 42 Mph, your 105 is doing quite nicely! In those earlier year Chrysler engines with 2 piece lower units I believe the only lower unit with a 2 to 1 ratio was the 90 horsepower three cylinder. What you are calling the fine-tune adjustment sounds like the timing adjustment link. if it is a threaded rod with a locknut and two black plastic pieces, THAT is the timing adjustment. If the timing is currently correct do not touch it.

 

[hbryant123]

Re: Efficiency increases

At 42 Mph, your 105 is doing quite nicely! In those earlier year Chrysler engines with 2 piece lower units I believe the only lower unit with a 2 to 1 ratio was the 90 horsepower three cylinder. What you are calling the fine-tune adjustment sounds like the timing adjustment link. if it is a threaded rod with a locknut and two black plastic pieces, THAT is the timing adjustment. If the timing is currently correct do not touch it.

Without going and looking its hard to say, but ik it has a lock nut and u can adjust it with a flat head screw driver, when u turn it it turns the distributor

 

[jimbo_jwc]

Re: Efficiency increases

Messed with mine ended up changing points ,rotor button ,distribureter cap , and new plugs , never messed with again .It was 120hp new power unit 130hp never rejeted it ran lean and hot and I could troll about ahalf hour before buzzer said stop and rev in neutral to cool . Drilled air intake holes larger and plugs like in Mazda RX7 wouldnt foul when choke solnoid quit with hand over carbs gase everywhere, fired right up smartly .Last thought before rejeting was to solder holes in choke butterfly shut . Friend Had racing lower unit but not sure what gear ratio but was higher than stock and didn't last long.

 

[Frank Acampora]

Re: Efficiency increases

Yep! That is how you change the timing. Don't mess with it. If you have already moved it, re-time the engine.

 

[hbryant123]

Re: Efficiency increases

well when i first go the engine going, i was out on the lake and turned it a ways as i had a friend drive and it didnt seem to do much, as for timing years ago my dad marked exactly were the proper timing was after he had borrowed the chrysler tool from an old mechanic we knew.

 

[jerryjerry05]

Re: Efficiency increases

The difference in timing you'd have to make so you could see/feel the difference is enough to start blowing pistons.
Put it back and then re-time anyway.
To check performance,efficency we need to know RPM's at WOT?
You should be running about 5200 -5500 at wot.
Load,condition of the bottom,compression all will effect performance.
I thought changing from 17 to 19p would get more speed and better performance.
I got about 3mph more and used 20% more fuel.

 

[Frank Acampora]

Re: Efficiency increases

Two years ago I saw one of those racing lower units go for 1600 bucks on ebay!

 

[hbryant123]

Re: Efficiency increases

The difference in timing you'd have to make so you could see/feel the difference is enough to start blowing pistons.
Put it back and then re-time anyway.
To check performance,efficency we need to know RPM's at WOT?
You should be running about 5200 -5500 at wot.
Load,condition of the bottom,compression all will effect performance.
I thought changing from 17 to 19p would get more speed and better performance.
I got about 3mph more and used 20% more fuel.

With my 13x19 i get decent mileage. better than when it was on my old tri hull. How is the best way to re-time it?

 

[Frank Acampora]

Re: Efficiency increases



Timing that engine is dirt simple and needs no tools. Assuming the block pointer has not been moved: Mark the wires 1 to 4 from top to bottom. Remove and ground all four plugs and wires. Put the control in wide open throttle. Now, with the ignition switch on slowly turn the flywheel until #1 (top) plug sparks. It should spark just as the 36 degree mark on the flywheel is at the fourth line to the left of the long line on the pointer. This will correspond to 32 degrees before top dead center. If it sparks to the right of this line, timing is too far advanced and set the link until it is back sparking at 32. If it sparks slightly to the left of the fourth small line, this would correspond to 30 degrees and that is OK.

This is the block pointer and distributor link. This particular pointer has only one line and there is a 32 degree mark on the flywheel. Turning the distributor ling so the plastic blocks come closer together retards timing. Spreading them apart advances timing.

 

[jimbo_jwc]

Re: Efficiency increases

Two years ago I saw one of those racing lower units go for 1600 bucks on ebay!

Only seen one in my lifetime and found pic on net . My fuel efficency was remarkable with whaletale on tri hull after using a couple years without .

 

[hbryant123]

Re: Efficiency increases

Only seen one in my lifetime and found pic on net . My fuel efficency was remarkable with whaletale on tri hull after using a couple years without .

oh wow, we used trihulls for years and they all were good boats, i switched to a 1991 vhull by rinker, i saw a speed increase and way better fuel efficiency, also i added power trim which is nice.

 

[hbryant123]

Re: Efficiency increases

View attachment 184291View attachment 184292View attachment 184293

Timing that engine is dirt simple and needs no tools. Assuming the block pointer has not been moved: Mark the wires 1 to 4 from top to bottom. Remove and ground all four plugs and wires. Put the control in wide open throttle. Now, with the ignition switch on slowly turn the flywheel until #1 (top) plug sparks. It should spark just as the 36 degree mark on the flywheel is at the fourth line to the left of the long line on the pointer. This will correspond to 32 degrees before top dead center. If it sparks to the right of this line, timing is too far advanced and set the link until it is back sparking at 32. If it sparks slightly to the left of the fourth small line, this would correspond to 30 degrees and that is OK.

This is the block pointer and distributor link. This particular pointer has only one line and there is a 32 degree mark on the flywheel. Turning the distributor ling so the plastic blocks come closer together retards timing. Spreading them apart advances timing.

Thanks for the info! In picture # 3 that is what i tinkered with last summer! Here in indiana its still cold and snowed last night so im not able to work on my boat any, once its warm i am gunna start with re-timing it and than syn the carbs and timing or should i do vice veresa? i hav ehad the distributor off before and idk how out of wack things are. Another question i have is how to set up the controls, Mine hang up a little when returning to neutral, it also jumped out of gear sometimes.