Mercruiser Drama

[hardlearner]

Help!! I have an old 75 Mark twain. it has a stock mercruiser outdrive for that year. I think it is early Alpha. I am in the process of installing a late model 01 305 FI out of a volvo. I have purchased and installed a aftermarket coupler that bolts to the one piece crank. Since the new motor has power steering I have purchased a different plate inside the transom to accept the power steering ram. (sorry, I do not know the correct term.) The exhaust goes thru the outdrive and I have that piece unbolted. It does not want to come apart and I am guessing it is because the exhaust bellow is still connected. If I buy the tool to take the pins out under the trim limiters will it come apart? I have the six bolts un-done on the inside and the bellhousing taken out. Also does anyone know how much trouble it is going to be to wire this engine. The harness is complete on the new engine and I am not sure if I will have to change out the instruments or not. Any help would be appreciated.

 

[Fishermark]

Re: Mercruiser Drama

Any help would be appreciated.

Welcome!

Basic help here would be to simply remind you that we need more information before any help can be given. "75 Mark Twain" doesn't tell us what outdrive, etc. Give a little more info.

 

[hardlearner]

Re: Mercruiser Drama

Sorry, It is a mercruiser. Stock unit for 1975.

 

[Bondo]

Re: Mercruiser Drama

I have the six bolts un-done on the inside and

Ayuh,... It should come right off, from your discription...
The components outside the boat aren't attached to the inner transom plate...

How much corrosion ya lookin' at,..??

 

[hardlearner]

Re: Mercruiser Drama

Not much corrosion. Everything has been coming apart pretty easy. I have the four bolts out that hold the (Y-pipe ?) on from the inside. Do not have a manual so did not want to buy any more parts than needed. The exhaust (Y) moves left to right but can not pull it out. Just figured maybe the bellow was holding it.

 

[Bt Doctur]

Re: Mercruiser Drama

see page 23 in here http://www.boatfix.com/merc/Install/gas/86419602.pdf
usually 4 bolts hold the Y pipe on and must be removed first before the inner/outer plates

 

[Fishermark]

Re: Mercruiser Drama

I have the six bolts un-done on the inside

I know there are a few changes in the years, etc... but I am fairly sure there should be 8 bolts / nuts - not six.

I will take a look at mine and post more info later.

 

[haulnazz15]

Re: Mercruiser Drama

Just make sure you get all of the Volvo parts to go with the engine. You are basically doing a complete swap from a pre-alpha leg/engine to a completely different engine/drivetrain platform. There won't really be ANY interchangeable parts between the two systems. Be sure to post some pics of the 'Twain and your progress.

 

[hardlearner]

Re: Mercruiser Drama

Thanks Bt Doctur, the pictures are worth a thousand words! I have forgotten some important info. The longblock I have to install is a volvo. Know most small block gms are the same. The intake and harness are supposed to be from a 01 mercruiser. All the pulleys and accesories are mercruiser as well. I will try tomorrow again to remove remaining parts from the transom and keep everyone posted. Thank you to all that have replied!!!
Hal

 

[Fishermark]

Re: Mercruiser Drama

Yeah - note from the manual that there are 8 bolts / nuts. Here they are:

 

[wallerus]

Re: Mercruiser Drama

I have done exactly what you are planning to do. There are some issues that you will need to address.
1. I don't know what year volvo engine you have. S/N would help me figure it out.
2. You will need your original bell housing from the merc.
3. You will need your original motor mounts from the merc.
4. You will need to remove the drive to be able to align the engine to the drive.
5. You will need to ensure the coupler you have is for the merc.
6. I don't know if a volvo steering actuator will fit a merc inner transom, I just bolted the volvo lines to the merc actuator. some years will fit.
7. You will need to replace the stud on the throttlebody to make the merc cable fit.
8. make a braket that mounts to the two outside bolts on the starboard riser to mount the merc shift plate if yours does not mount to the transom.
9. You will need to remove the impeller in the raw water pump of the volvo because the merc has the pump in the drive.

The 10 pin connector for your boat will plug right into the volvo harness and work.

YOU MUST find the plug on the back of the volvo harness for the shift interupt and splice it into the merc interupt on the shift plate.

The water inlet hose from the transom to the volvo p/s cooler will need some adaptaion to work right. If it comes off in the water you will sink.

The volvo engine you are using is several generations behind what they are using now and are hard to get parts for.
Get an extra fuel pump
Get an extra ECM

Carry them with you.
Ensure your antisiphon valve is good
Relace or at least drain the v/p fuel filter regularly
Keep water out of the fuel system.

Good luck, you will be very pleased with the change to fuel injection and if maintained properly will be worry free.

 

[cr2k]

Re: Mercruiser Drama

Was the old engine a V8? if not you will need to replace the outdrive with one with correct gear ratio, you need 1.5. in '75 it would not be an Alpha, but a pre alpha like an R or MR. And will not hold up well to higher HP.

 

[hardlearner]

Re: Mercruiser Drama

Okay, The only thing that I have that is Volvo is the longblock. The intake, throttle body and harness is all mercruiser. It is supposed to be 2001, not sure how to verify that. The remote oil filter,brackets, p/s pump, all mercruiser.The old outdrive was from 1975 and originally had a 350 carburated motor. I see now that I will have to get the Y-pipe off to get those two bottom bolts off. The steering I have is also mercruiser. I have a later model inner transom as the old one does not have the pins to hold the steerin actuator. Really the only thing volvo I have is the longblock. I can get the s/n but do not think that matters. Maybe I am wrong. Again, Thanks to all. I at least think this is pretty doable now. I was a little worried at first. The fuel pump is also mercruiser that is bolted along the cooling hoses. Maybe when I get this done there are some berkley wiz's out there. Thanks again!!

 

[hardlearner]

Re: Mercruiser Drama

Thank you very much. The harness, trottle body, fuel pump, p/s pump and actuator and all accesories are mercruiser. The pin looked like it would work but looked like there were more pins in one than the other. I put more info on my response in the thread but just wanted to thank you personally for the help. At least I know it is do-able. Do you have to change the old gauges?

 

[Bondo]

Re: Mercruiser Drama

Really the only thing volvo I have is the longblock.

Ayuh,... In that case, None of it is Volvo,... 'cept maybe the Paint...
The Long Block is All Chevy....

You seem to be headed the right way, but I'm bettin' yer gonna find Abunch more Gotchas before it runs...
Width of the rear motor mounts comes to mind,...
The 75 is 15", 'n the Gen.II is 9"...
You'll need a late model flywheel cover to match the newer inner transom plate....

The Y-pipe, may or may not be close enough to fit...

 

[hardlearner]

Re: Mercruiser Drama

I have the old 75 drive and bellhousing. I used a aftermarket coupler that fits the new one piece rear main and is supposed to work with the old outdrive. All that worked fine but I wanted to go the extra mile and have the power steering. Thus, that is why I am trying to get the inner transom off to change for a model that I can use the mercruiser power steering. I am hoping other than the wiring that will be all of the surprises but it is a boat after all so I am just hoping!

 

[Bondo]

Re: Mercruiser Drama

I am hoping other than the wiring that will be all of the surprises but it is a boat after all so I am just hoping!

Ayuh,... I just pointed out 2 issues that Are a problem....
If you've got the Merc flywheel cover for the New motor, 1 of 'em is behind ya....

Just sayin'....

 

[hardlearner]

Re: Mercruiser Drama

Not sure what you mean about flywheel. I have the flywheel and coupler bolted up. I just put the old bellhousing on and fits no problem. Thanks Fishermark, transom plate comes off easier when the two bottom nuts are taken off. Have it split but still can not get the Y pipe off. the exhaust y will rotate a little right to left but will not come off. That makes me believe I have the bolts all off. Four I believe. I hope I can post a couple of pics. I am not smart enough to post the pics. They are in J-peg and must be to big to upload. Sorry/

 

[wallerus]

Re: Mercruiser Drama

Don't quote me on this but IIRC the older mercs had 5 bolts holding the Y pipe. One hiding up in between the the humps. Been a long time but I think you missed one.

 

[Bondo]

Re: Mercruiser Drama

I just put the old bellhousing on and fits no problem.

Ayuh,... What you're calling the Bellhousing, is the Flywheel Cover....
It has the Rear motor mounts on it...
If you had a 1975 mod.1, the Flywheel Cover rear motor mount bolt spacing is 15".....
The New inner transom plate you're putting on, has the rear motor mount spacing at 9"....

It Won't Fit....

I am not smart enough to post the pics. They are in J-peg and must be to big to upload. Sorry/

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