Cracked my out drive need help on a replacement

[Ogbign]

I’ve got an old 1978 imp with mercruiser it has the 4.3 on it from running the numbers the engine is 1989-1990 so it’s far from original I bought it with broken starter bolts after getting those extracted had it in the water, the outdrive somone had welded to it before an it didn’t hold. So I’ve found another one In great shape but it’s got a 3.0 on it. Which I believe is what mine had originally but idk I did get some numbers off my drive but idk how to find an gear ratios. Or should slap the other one on an just go for it ???

 

[Scott06]

Normally a 3.0 and 4.3 would have different ratios drives - 4.3 would be 1.81:1, 3.0 would be a 1.98:1.

The ratios should be stamped on the port side of drive by vent plug. Usually in the sticker and stamped in housing as well. With an older drive these may be hard to read, in that case you can always remove the top cap and count teeth as the reduction is in the upper.

In the event they are different ratios likely you can prop around one ratio step. I repowered a boat that had a 4.3 w/ 1.81 drive to a 5.0 engine- kept the drive a stepped up from 19" to 21" pitch. It hits WOT rpm perfectly.

 

[Ogbign]

The only numbers I can find is A 665138
Propeller says BS. Pro Mak M 14-1/2x19 an what if this boat did have the 3.0 with this drive am I looking at a huge difference?

 

[Ogbign]

Ok so I was told I have alpha 1 gen 1 drive with a gen 2 bell housing .. is this possible?

 

[havoc_squad]

Ok so I was told I have alpha 1 gen 1 drive with a gen 2 bell housing .. is this possible?

No, Alpha one gen 1 and gen 2 cannot inter-mix on the outdrive or transom assembly.

Alpha one gen 1 and MR-1 (generation before gen 1) can inter-mix with some changes, I believe it is the outdrive yoke length.

Others can go into more detail about this.

 

[Fun Times]

The only numbers I can find is 0A665138

0A665138 suggests the stern drive to be an 1986 MERCRUISER MC1, (1.50:1) Model Number 01509016.

Lets see some pictures of the drives and bell housing/transom of the boat as it may help some... Engine too.

 

[Ogbign]

Engine numbers show its 88-91

 

[Ogbign]

Engine numbers show its 88-91

Boat is a 1978 imp

 

[Ogbign]

So about all the 4.3s show a 1.81 gear drive, the v8 s show 1.47 ..? So mine isn’t correct to start with … ? The drive off the 3.0 would be much closer gear than what I have now ..?

 

[Scott Danforth]

Some 4.3s use the 1.81 some use the 1.62

The drive from a 3.0 may work, however I would not use it myself

 

[Ogbign]

So I had this boat on the lake the other day before the crack on the drive, get it in gear an moving an she just stood up felt like if I had put it full throttle I woulda sank the back of the boat just set down so far, so I had to baby it to get up on a plain which took a while also first time ever running this boat, maybe operator error ? Boat is a 1978 17ft with a 1986 drive an a 1990 engine. Boat is old an can’t find much info for it so probly only god knows what it came with factory. Anyone else have a 4.3 with 1.50 drive ?

 

[Scott Danforth]

So I had this boat on the lake the other day before the crack on the drive, get it in gear an moving an she just stood up felt like if I had put it full throttle I woulda sank the back of the boat just set down so far, so I had to baby it to get up on a plain which took a while also first time ever running this boat, maybe operator error ? Boat is a 1978 17ft with a 1986 drive an a 1990 engine. Boat is old an can’t find much info for it so probly only god knows what it came with factory. Anyone else have a 4.3 with 1.50 drive ?

some small 16-17 foot very light-weight go-fast boats were made with a 4.3 with a 1.47:1 drive. I believe the Donzi Sweet 16 came with such a setup. however it would not be the norm. the 1.57:1 drives were normally paired with a 5.7 liter

your IMP would have came with either a 470 4-cylinder with a 1.81:1 drive or the 165hp inline 6 cylinder and a 1.62:1 drive back in 1978

 

[Bondo]

So I had this boat on the lake the other day before the crack on the drive, get it in gear an moving an she just stood up felt like if I had put it full throttle I woulda sank the back of the boat just set down so far, so I had to baby it to get up on a plain which took a while also first time ever running this boat, maybe operator error ? Boat is a 1978 17ft with a 1986 drive an a 1990 engine. Boat is old an can’t find much info for it so probly only god knows what it came with factory. Anyone else have a 4.3 with 1.50 drive ?

Ayuh,...... Welcome Aboard,...... That's what boats do, it won't sink, as the forward motion won't allow it too,.....
My ole tin fishin' barge was a 21' starcraft islander, 'n I experimented with drive ratios,.....
I ran it over 20 years with a 1.65:1,..... It was Ok, but a 1.84:1 would have allowed me to run a taller prop,.....
I tried a 1.98:1, with a 26" prop,..... it went slowly, 'n loudly, a bad choice,.....
With a 1.50:1, I couldn't find a prop small enough to get respectable performance from it,....

With a 17' boat, I'd think the ideal ratio will be 1.65:1,....
A 1.84:1 will be tolerable,....

 

[tank1949]

The only numbers I can find is A 665138
Propeller says BS. Pro Mak M 14-1/2x19 an what if this boat did have the 3.0 with this drive am I looking at a huge difference?

Turn the drive shaft and count the prop spline revolutions.

 

[Ogbign]

Ayuh,...... Welcome Aboard,...... That's what boats do, it won't sink, as the forward motion won't allow it too,.....
My ole tin fishin' barge was a 21' starcraft islander, 'n I experimented with drive ratios,.....
I ran it over 20 years with a 1.65:1,..... It was Ok, but a 1.84:1 would have allowed me to run a taller prop,.....
I tried a 1.98:1, with a 26" prop,..... it went slowly, 'n loudly, a bad choice,.....
With a 1.50:1, I couldn't find a prop small enough to get respectable performance from it,....

With a 17' boat, I'd think the ideal ratio will be 1.65:1,....
A 1.84:1 will be tolerable,....

Ayuh,...... Welcome Aboard,...... That's what boats do, it won't sink, as the forward motion won't allow it too,.....
My ole tin fishin' barge was a 21' starcraft islander, 'n I experimented with drive ratios,.....
I ran it over 20 years with a 1.65:1,..... It was Ok, but a 1.84:1 would have allowed me to run a taller prop,.....
I tried a 1.98:1, with a 26" prop,..... it went slowly, 'n loudly, a bad choice,.....
With a 1.50:1, I couldn't find a prop small enough to get respectable performance from it,....

With a 17' boat, I'd think the ideal ratio will be 1.65:1,....
A 1.84:1 will be tolerable,....

This helps

 

[Ogbign]

I found a replacement outdrive with these numbers 0C853567 can anyone find any info on it ?

 

[ddrieck]

My 1986 Thompson has the 470 and the 1.65 outdrive. I ordered a new complete upper and lower from SEI (Sterndrive Engineering) last season when the input bearings in the in the upper drive locked up and seized. Might be a solution to your problem by getting a lower unit from them. Bit on the pricey side however.
You can call and talk with their tech support to see what gear ratio you should be running with your engine.

 

[Ogbign]

Can’t justify buyin a pricey new one for something I haven’t drove but only once when I’m not sure which gears I need. No used one would last forever. But if I could get it back on the water with a gear ratio I loved I would absolutely buy a pricey new one. I’m sitting with the 1.50 ratio and another set I’m unsure of and not sure if either one are even close to what I need. And how much is pricey ? Does anyone have any pics of a new unit an what it will come with ? I don’t want to go cheap I want it correct but I’m not gonna buy 3 new units. if that helps

 

[Ogbign]

My 1986 Thompson has the 470 and the 1.65 outdrive. I ordered a new complete upper and lower from SEI (Sterndrive Engineering) last season when the input bearings in the in the upper drive locked up and seized. Might be a solution to your problem by getting a lower unit from them. Bit on the pricey side however.
You can call and talk with their tech support to see what gear ratio you should be running with your engine.

My 1986 Thompson has the 470 and the 1.65 outdrive. I ordered a new complete upper and lower from SEI (Sterndrive Engineering) last season when the input bearings in the in the upper drive locked up and seized. Might be a solution to your problem by getting a lower unit from them. Bit on the pricey side however.
You can call and talk with their tech support to see what gear ratio you should be running with your engine.

Where can I find info on a pricey new one ?

 

[ddrieck]

Where can I find info on a pricey new one ?

Just google Search "Sterndrive Engineering".
Like I had said you can talk with their tech specialists and then go forward looking for a good used unit or get a new drive unit. Lots of options once you know what to look for