Just picked up a 125hp

Hi guys,

Just picked up a 125hp to replace my 105hp as the gearbox went and i couldn't find a 2 peice gearbox anywhere. managed to get a 125hp really cheap with perfect bores.

The engine code is 1258H1A, from what i can tell its from 1981, It has CDI, is CDI much better than the magna power system? my 105HP had magna power igition.

How reliable is the CDI and what are the advantages.

im excited to see how a 20hp upgrade goes on my tiny 3.9m boat.

Re: Just picked up a 125hp

First, I would not be surprised if you get 8 MPH faster. The one piece lower unit is, by itself, at least 3 MPH faster than the two piece lower unit. Then, you are adding 20 HP.

The Magna-Power II ignition was a trouble prone ignition that failed quite frequently. Some did last for the life of the engine though. BUT: Did you have Magna Power II? Chrysler used the term "Magna Power" quite loosely. Even the Motorola-Distributor ignition was labeled Magna Power.

Prestolite is no better than Magna-Power II from a horsepower viewpoint. It is slightly better than distributor ignition. It is better in that if a component fails, you can replace only that component and they are available.

Re: Just picked up a 125hp

There are a lot of wire connections on the Prestolite ignition system. It's not a problem, but sometimes when you start swapping the CD modules around to trouble-shoot, it's not uncommon to get the wires mixed up and cause some real problems. Other than that, it's OK.

125HP Force on a 3.9M boat. That's about 12.75ft. Is you transom rated for that big of an engine? If not, it may rip the transom right out. It should really fly!!

Re: Just picked up a 125hp



I got locked out last time I tried to post a photo so here goes again:

Your boat is approximately 13 feet long. Post a couple of photos. Here is a 14 foot hull with a 125 on it. She tops out at 60.

Re: Just picked up a 125hp

had it been on the other side of the Yarra l would have bid on it instead of just watching it,
need a cheapie quick!
LOL

Re: Just picked up a 125hp

haha, Chrome dome i take it you saw it on ebay?

Here is a few pictures with the 105 on
https://dl.dropboxusercontent.com/u/45850904/boat/IMG_3247.JPG
http://i29.photobucket.com/albums/c295/paradox616/2013-02-03103545_zps9e1a64b8.jpg
https://dl.dropboxusercontent.com/u/45850904/boat/521621_10151253679232400_284800425_n.jpg

We topped it out at 43 MPH (via GPS) on a choppy day with a 17 pitch prop. If i could hit 50mph ill be really happy.

Not sure if i had magnapower II or what, it did have a dissy+ignition module and a single coil.

Bores are quite good on the 125hp, just waiting on a few parts before i install it. winters coming so hopefully i can sneak in a few trips before it gets too cold.


does anyone know where to get new hood decals?

Re: Just picked up a 125hp

yeh mate, saw it on ebay, sounds like you got a bargain
needed a good size cheapie to get my project Savage Pacific half cab registered so could take it on the Tassie ferry when we move down there in 2-3 months but Oakleigh was just too much drama with Ring rd/ Tulla roadworks,

my younger son has just put a 105 Chrysler on a Volero Dart and if he can get those sorts of speeds he will be a happy camper..hasn't been able to try it out yet

your 105 isn't a Magnapower 11 , no dizzy on those,
son had a Magnapower 11 120 no end of drama with that, as Frank says, ended up doing a head gasket but it was a pain in the bum anyway with that ignition system,sometimes had spark on all 4 then only two and then back to 4, changed triggers, ok for awhile then back to drama... nearly made me drink cheap wine..

boat looks really good, if you don't mind me asking what paint did you use and where from ( other son has a Volero Dart as well that needs painting )

cheers

not sure about decals

Re: Just picked up a 125hp

chrome dome said:

yeh mate, saw it on ebay, sounds like you got a bargain
needed a good size cheapie to get my project Savage Pacific half cab registered so could take it on the Tassie ferry when we move down there in 2-3 months but Oakleigh was just too much drama with Ring rd/ Tulla roadworks,

my younger son has just put a 105 Chrysler on a Volero Dart and if he can get those sorts of speeds he will be a happy camper..hasn't been able to try it out yet

your 105 isn't a Magnapower 11 , no dizzy on those,
son had a Magnapower 11 120 no end of drama with that, as Frank says, ended up doing a head gasket but it was a pain in the bum anyway with that ignition system,sometimes had spark on all 4 then only two and then back to 4, changed triggers, ok for awhile then back to drama... nearly made me drink cheap wine..

boat looks really good, if you don't mind me asking what paint did you use and where from ( other son has a Volero Dart as well that needs painting )

cheers

not sure about decals

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Thanks! I didn't paint it the previous owner did so im not %100 sure, the paint has enamel in it and has been applied pretty thick. i picked up the boat for dirt cheap with all the gear as the guy selling it was moving overseas and really had to get rid of it quickly, the 105 powerhead had a full rebuild and has been going flawlessly.. i wish i could say the same for the gearbox..

apart from that all i've done is fitted some instrumentation as it had none.
The boats a haines hunter and has a fairly good wake for a small boat and is very easy to control


There is a few small things that needs fixing on the engine, ordered a new headgasket for it last night.
piston #3 has some pitting on it. I'm guessing at some point it ran lean.

Re: Just picked up a 125hp

That's a tiny boat.How long?
Does it have trim/tilt?T/T will add 5mph.
I've seen a couple of fishing shows or was it the cop shows?
Anyway,You Aussys go out in some really tiny boats???
Saw the cops try to arrest 3 FAT guys in a 15 ft.They were out quite a ways from land.
I'd be afraid to put that in my tub

Re: Just picked up a 125hp



My experience with the 14 footer in the above photos (last answer) was this: With a two piece lower unit, 85 Chrysler, distributor ignition, it topped out at 38 MPH. As soon as I installed a 1990 Force 90 HP with a Prestolite ignition, top speed went up to 55 MPH. Then, a 1990 Force 125 took it to 60.

Now, my boat is a flat bottom and yours is a deep vee. and a bit smaller. Smaller boats are more sensitive to loads and you look like two strapping lads, and deep vees need more power. However, with the correct prop--13 X19 or 21, 17 pitch is too low, I suspect that the 125 will move at more than 50. Prop it so she turns at 5500. She likes to run fast. Definitely buy a stainless prop--that alone is good for about 100 RPM and 2 MPH more than aluminum of same pitch.

here are a couple of photos of a 15 footer that tops out at 45 with a one piece 105. The other photos show the reinforcement I did to the transom. You should consider reinforcing too.

NOW: The lower transom bolt holes will line up with the new engine clamps. Mount the engine so the antiventilation plate is one inch above the point of the Vee. You should use the top holes at the bottom of the transom clamp so you can raise the engine another inch if you want to try that. Either If your 125 has the newer style clamps, either coat the bolts and top holes well with silicone RTV to prevent (hopefully) internal corrosion and ultimately splitting of the clamps, OR do yourself a favor and replace the clamps now with the older style off your 105 Look closely at the fourth photo and you will see the white transom clamps on my 125 (marked 85).

Re: Just picked up a 125hp



This photo shows the transom reinforcement on the outside and the new style clamps which I replaced. The engine is also sitting down on the transom instead of being raised one inch.

You can clearly see the (illegal in my state) exhaust cut-outs in the lower unit. They really don't do much and simply make the engine louder so don't really bother with the.

Re: Just picked up a 125hp

Frank Acampora said:

View attachment 188947View attachment 188948

This photo shows the transom reinforcement on the outside and the new style clamps which I replaced. The engine is also sitting down on the transom instead of being raised one inch.

You can clearly see the (illegal in my state) exhaust cut-outs in the lower unit. They really don't do much and simply make the engine louder so don't really bother with the.

Click to expand...

Thanks for the wealth of information frank!, i did notice the two holes on the transome mount, i was already considering swapping frames as all 3 bolts have been snapped off for the hydraulic lift pump, and yes the engine does have trim, I've also got hydro foils which work wonders for keeping the boat stable, if i turn too hard or its choppy when turning and air gets under the hydro foils the boat is unstable, other than that it is extremely easy to control..

My transom has already been reinforced in the past most likley when the 105 was put on, the Haines hull's are considered to be one the best aswell availiable. i will definately coat the bolts in silicon to prevent corrosion.

i thought 17 pitch was a bit too low as it had awesome holeshot but then kind of hit max speed or %90 of max speed in a few seconds, 45mph was achieved @ 4500rpm too in the 105.

The problem i had with the 2 peice lower unit was the 18 spline prop's are not sold new so i had to put up with what i could find and all i could find was 17 pitch.

the new leg SHOULD have a 19 pitch on it. atleast its 15 spline so i can get my self a new prop.



I've read a few threads you posted in frank about the importance of the engine placement and i'll make sure its mounted right as my goal is MPH


Although my boat is a 12ft it still has a decent amount of room in it, the bow isnt oversized and the transom is not too long. there is some serious reinforcements under the transom aswell, looks like someone went to a bit of an effort to make sure it didnt break.

Re: Just picked up a 125hp

jerryjerry05 said:

That's a tiny boat.How long?
Does it have trim/tilt?T/T will add 5mph.
I've seen a couple of fishing shows or was it the cop shows?
Anyway,You Aussys go out in some really tiny boats???
Saw the cops try to arrest 3 FAT guys in a 15 ft.They were out quite a ways from land.
I'd be afraid to put that in my tub

Click to expand...

Bigger isn't always better

Re: Just picked up a 125hp

12ft, WOW.
I;m not a fast boater.
Went for a ride in a friends boat.
21 ChrisCraft Scorpion???I know it was a Chris Craft?
It had a 502 with a Brovo drive.
We had to lean out on the front to bring the bow down.Then all hell broke loose!!!
We were doing over 60 and I asked him to slow down.
I fix em.Don't like em fast.

Re: Just picked up a 125hp

jerryjerry05 said:

12ft, WOW.
I;m not a fast boater.
Went for a ride in a friends boat.
21 ChrisCraft Scorpion???I know it was a Chris Craft?
It had a 502 with a Brovo drive.
We had to lean out on the front to bring the bow down.Then all hell broke loose!!!
We were doing over 60 and I asked him to slow down.
I fix em.Don't like em fast.

Click to expand...

hehe, never had any issues like that, the hydro-foils seem to keep the front end down on a holeshot.

Turns out i have a few frames, i see what you mean by multiple bolt holes for mounting and i see the leg is 1" shorter

Re: Just picked up a 125hp

Some say the hydro foil actually slows you down??
In some cases I can see it.Slower operation.
Getting on plane.
If it was a good thing??Then the manufacturer would have made it into the motor?

Re: Just picked up a 125hp

jerryjerry05 said:

Some say the hydro foil actually slows you down??
In some cases I can see it.Slower operation.
Getting on plane.
If it was a good thing??Then the manufacturer would have made it into the motor?

Click to expand...

That is a very valid point, I might leave them off for a while and see how it performs.

Well its installed just gotta wait for a free weekend to get it in the water. The cavitation plate is about 1/2 an inch betlow the hull which i believe is almost perfect?

Re: Just picked up a 125hp

If you are looking for speed, jack it up higher! One inch above the vee or even higher if it will take it without ventilating.

Re: Just picked up a 125hp

Frank Acampora said:

If you are looking for speed, jack it up higher! One inch above the vee or even higher if it will take it without ventilating.

Click to expand...

I see, well the new frame has 2 set of bolt holes, i could easy move it up about a inch which would bring the cav plate above the vee. maybe i'll give this a shot.

Re: Just picked up a 125hp

chrome dome said:

need a cheapie quick!
LOL

Click to expand...

you can stop looking now LOL...
found one...a now running ( 20 mins ) 90 with 150 lbs on all three...looks a bit small on a 16 ft 6" half cab but it will do for the time being,
continue with normal programming now...
LOL