Engine swap questions

[GasGasXC]

I have an older Harvey Dory crab boat that had a 2001 mercruiser 1.7 diesel hooked up to the same era Alpha 1 second gen.sterndrive
The turbo overboosted because the waste gate actuator quit working and so I blew the engine.
Im trying to get this boat back in the water and working asap I only have a few weeks left in the season.I bought a 1974 Seaswirl with a 140 HP 4 cyl bolted up to an older mercruiser stern drive of the same era.Its a good runner and a complete boat.
So my questions are
1.If I wanted to use the engine and outdrive together out of the Seaswirl will the bolt patterns on the through transom bolts be the same.
If I did this looks like I need to do some forward motor mounts and change the steering setup.I currently have hydro steering for the Alpha 1.Everything else looks pretty straight forward.May need to change the shifter also.

2. Will the 1974 140HP bolt up to the alpha drive?.This would save me a ton of work besides the Alpha being a better outdrive for my boat.Would also allow me to use the same lift pump that is bolted independently and more importantly would allow me to use my steering setup.And save time swapping the sterndrives.

3. I have a few more questions but I will stop here and wait for answers to #1 and #2.They are the most importand and urgent considerations.I commercially fish the boat and have a short season left so Im looking for the quickest way to get the boat back in the game.

I thank all of you Mercruiser Wizards in advance.
Please only for sure information based on experience and practical application.In other words.Youve done it.I don't have time for I think you can do this and Ive heard you can do that.Thx again in advance

 

[GasGasXC]

Also I believe and will verify asap that the alpha 1 is a 2.0 gear ratio.
The 140 hp is a 1.81 or a 1.84 I believe.
I have the outdrive serial number off the older mercruiser drive but couldn't get it to come up on any websites with any usable information specific to that drive-I.E. model year gear ratio etc.

 

[GasGasXC]

Update-looks like it might be an R-drive and with the 2.5 4cyl its 1.98 ratio.So for me if the Alpha 1 can remain in the boat and the 1974 140 HP will bolt up to it.Then the 2.0 vs. 1.98 gear ratio is close enough for me.Its a work boat.

 

[Bondo]

Ayuh,.... If the newer drive is 2:1, all you need is a late model flywheel cover to drop in the 3.0l, 'n possibly a later model coupler,...
The older rear motor mounts are considerably wider,...

The steering shouldn't care, or matter,...

 

[GasGasXC]

Ayuh,.... If the newer drive is 2:1, all you need is a late model flywheel cover to drop in the 3.0l, 'n possibly a later model coupler,...
The older rear motor mounts are considerably wider,...

The steering shouldn't care, or matter,...

So I mistakingly put in 1983 140 HP engine to swap instead of 1974 140 HP.
I have the engine serial number but the specific year wont come up.
Looks like a long run of Chevy 4 cyl. engines
I believe I have the early 2.5.

So back to your response.
Im unfamiliar with the couplers and flywheels on these things.But if I am understanding you correctly you are saying get some later model stuff for the Chevy 4 and bolt it on and then Im basicly good to go.

By later model---would a 1990 4.3 merc ruiser setup with an early Alpha 1 sterndrive have the rest of what I need?
I can buy the complete boat on a trailer everything is still bolted up.


As far as steering goes.The boat is heavy and its a working crab boat so lots of turns and working in close quarters.The Hydraulic steering I have mounts to the inner Alpha transom plate by 2 bolts top and bottom.The early Mercruiser set up uses an old school manual push pull style steering set up.

Maybe there is a kit I can buy and use my steering on the older drive plate.But Im on a time line.

Also I have a pto double belt pulley I need to mount on the front of this engine to run the Hydraulic pump.I don't have room with the forward motor mount set up.So I am going to have to build side mounts to mount the forward part of the engine to the stringers.Are there any aftermarket side mount motor mounts for the 2.5 chevy available.Maybe theres another route I could go?? Some sort of automotive industrial application that uses the same engine??

Any help with this is greatly appreciated.

 

[Bondo]

By later model---

Ayuh,.... 'bout '83 or newer have the narrower rear motor mounts,....

In '90, or '91, the crankshaft got a 1 piece seal, so the flywheel bolt pattern changed,....

Any room to mount the hyd. pump down low, starboard side,..??
It could run off the same single belt,....

No other front mounts used that I know of,....
Might have to engineer yer own,...

 

[GasGasXC]

I appreciate the help here.But as I dig into this deeper and begin to take things apart------.im finding small details yet extremely important details that I am not hearing about from the Mercruiser Wizards.
Example.The 1974 Mercruiser 140 HP engine has a singlethrottle cable that goes to the engine.
The second throttle cable goes to a shifting plate mounted on the transom.
The Alpha 1 Gen 2 shifts via a shifting matrix on the throttle linkage.
This is significant unless someone makes an aftermarket bolt on or I can source a newer model engine with the shifting linkage integrated into the throttle linkage.

Anybody???
That's actually done this swap---Is familiar with the details??
I appreciate the help so far but Im getting down to it and finding problems.
Anybody else know whats coming down the line.??

I do not want to get farther don the line on this and run into another issue.
Looks like I may have to move this linkage plate somewhere else and find a place to bolt it on out of the way.

 

[Bondo]

The Alpha 1 Gen 2 shifts via a shifting matrix on the throttle linkage.

Ayuh,.... I've worked on alota Alpha 1 Gen.IIs, 'n every one of 'em had a throttle cable to the carb, 'n a shift cable from the controller to a swirch plate, then the lower shift cable from the switch plate to the drive,....

Granted, I've never seen the diesel motor yer pullin',...

Post pictures of what yer seein',....

I am confused, as I thought you were usin' an '83 3.0l,....

 

[GasGasXC]

Well.Turns out there is quite a bit of misinformation in these threads.Not sure the hands on experience of some is quite there.Ive only been p[laying with Mercruiser outdrives for about a week and Im telling new guys and those of you that are just learning this stuff to do your homework.

 

[GasGasXC]

Started out with a 2001 1.7 Mercruiser DTi diesel hooked up to a Alpha1 gen 2 drive.Purchased a 1974 Seaswirl with a 2.5 140 HP and an early Mercruiser drive.Yes some things will interchange and if you rounded up enough crap from different setups and did some mods you could shoe horn that thing in there and end up with something.But it is completely impractical of a swap and your just going backwards.I cud shoe horn a helicopter engine in there too.

 

[GasGasXC]

So heres whats happening now a week later.I bought another boat.Its a 1990 with a 4.3 with a Alpha 1 gen 1 drive.The Gen 2 had 2.0 ration.The gen 1 has 1.84 ratio.The gen 1 drive has very low hours and is in excellent condition.But it has a pump driven power steering set up and I would have to swap out everything once again.So I am attempting to put the 4.3 inplace of the diesel and hook everything up to the Gen 2 Biggest thing here is I found a 4.3 set up with NO TRANSOM MOUNTED SWITCH PLATE

 

[Bondo]

Turns out there is quite a bit of misinformation in these threads.

Ayuh,..... That's a pretty tall charge, considerin' you said Nothin' about what yer seein' in yer boat, much less explainin' what you've learned elsewhere,.....

The Merc Diesels are rarely seen on this side of the pond, none in my area, I've never encountered 1,....
I'm goin' on messin' with gas powered Merc drives,....

Pictures, or a better explanation of what yer seein' would help,....

 

[Bondo]

Biggest thing here is I found a 4.3 set up with NO TRANSOM MOUNTED SWITCH PLATE

Ayuh,.... Use the 1 from the 2,5l motor,.....

 

[GasGasXC]

Yeah.Anyway.
No pictures necessary.May be helpful.But the information is simple.
Going from 2001 Mercruiser DTI diesel with an Alpha 1 Gen 2 drive to a 1974 2.5 140 HP with and older stern drive and a transom mounted shift plate and cable steering makes absolutely no sense in everyway.Too many differences.Some stuff works but overall-motor mounts-shifting-steering wiring etc.NO SENSE.This is for the people like me who come in here looking for information and have little to no experience with these Mercruiser setups.Ive been through 3 boats in the last week and Im getting a pretty decent idea of what makes sense.what can be practically done and what cannot.

 

[GasGasXC]

Here is where the project stands.I canned the 1974 straight swap the 2.5 and the early Mercruiser drive for the 2001 Mercruiser diesel and Alpha 1 Gen 2 drive.Sold that donor boat.And bought a 1990 Bluewater with a 4.3 and a Alpha 1 Gen 1 drive.With a total time of 162 hours.The 4.3 has no switch plate and shifts more like my 2001 setup.I will be able to use my later model shifter with remote on this setup.After reading through the threads and Ive read through plenty to try and eliminate the iffy information and confirm through redundancy the usable information as it applies to my situation.What I can come up with is that the early Alpha drive even though it is tight and in excellent condition is not the way to go for a few reasons.I am going to try and mount the 4.3 to my worn out Gen 2 Alpha.This will allow me to retain my Hydraulic steering in place-Use my later model shifter with remote-Leave the lift pump in its current location and plug and play on the shifting set up since this 4.3 uses no transom mounted shift plate and is more akin to what was in the boat.

 

[Bondo]

So I am attempting to put the 4.3 inplace of the diesel and hook everything up to the Gen 2 Biggest thing here is I found a 4.3 set up with NO TRANSOM MOUNTED SWITCH PLATE

Going from 2001 Mercruiser DTI diesel with an Alpha 1 Gen 2 drive to a 1974 2.5 140 HP with and older stern drive and a transom mounted shift plate and cable steering makes absolutely no sense in everyway.Too many differences.

Ayuh,....Ya wanta put the 4.3l into the boat, or what,..??

If so, just use the shift switch from the 2.5l that yer not gonna use,....

'n just What are you callin' Bad Information,..??

edit; Do each of these motors have a Shift switch plate, regardless Where it's mounted,..??
It don't matter where it's mounted, so long as it's there,....

 

[GasGasXC]

Here are the challenges still.Forward motor mounts and alignment.Its close not exact.I haven't dug deep enough back in there to measure the rear mounts.Alignment-And the gear ratios are a little off.The Gen 2 is 2.0 and the Gen 1 is 1.84 which seems to be the standard v6 ratio.Ive seen 1.81?Anyway right in that ballpark.Theres a y pipe on the 4.3 gen 1 setup my Mercruiser diesel was a straight 4.So how that lines up I do not know.and whatever else I run into.Ill keep the bopard posted.This swap makes way more sense and is well worth the effort.Ill let the board know how it goes step by step.

 

[Bondo]

So, yer goin' with the 4.3 motor, 'n the existin' transom, 'n drive,..??

The rear motor mounts, Should be the same,....
The y-pipe Should bolt up to where the diesel's down-pipe bolts to the transom housin',...

It's gonna take a monster of a prop to connect the power through a 2:1 drive ratio,....
!.81/ 1.84:1 in a heavy hull for a 4.3 motor,....
1,65:1 in a light hull,...

To find where the front mounts go, hang the 4.3 off the rear mounts, 'n slide in the alignment bar,....
Measure to the bottom of the iron pads, 'n build out the hull-side to match,....

 

[GasGasXC]

I am going to start a new thread as the direction of this swap has changed.
A couple things to note.
1. All alpha drives DO NOT use a transom mounted shift plate.
2. Better to stick as close as you can with years when interchanging this Mercruiser stuff.Its an evolution in engineering.And yes some older stuff will interchange with some of the newer stuff.But generally only in part.In other words you can get part of the way but it is gonna be tough to get all the way and have the dots connect when interchanging 40 year old stuff.IE The 1974 Seaswirl with a 140 HP 2.5 and an older stern drive with a 2001 1.7 cummins turbo set up mated to an Alpha Gen 2.Thats a dead end

Starting a new thread

 

[Bondo]

1. All alpha drives DO NOT use a transom mounted shift plate.

Ayuh,.... I never said they did,.... That's on ole MC-1 thing,....
The 2.5l motor ya got, Pre-dates the Alpha drives,....
That's when the rear motor mount spacin' changed too,....