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Old 04-30-2020, 09:15 PM
Dtgorrell Dtgorrell is offline
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Boat: 1991 mastercraft prostar190 351w
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Engine replacement

Okay guys, Its finally time to drop in a new short block in the 91' prostar190. I posted awhile back about having water in the oil and ended up finding a huge crack in the lifter valley. Since then I've disassembled everything I can with the engine still bolted down. Heads have been removed and gone through, exhaust manifolds, intake manifold, alternator, starter, water pump, timing cover, wiring, etc etc. Alternator and starter checked out good. I've ordered all new gaskets, carb renew kit for the 4160, oil pressure sending unit because I snapped it off. I have everything disconnected and ready to pull this weekend. I'll be ordering a 351w short block from rapido marine in the next week or so, wanna make sure I have all my ducks in a row when it gets here. I've never pulled a boat engine, but I assume once the bell housing bolts and mounts are loose it should lift right out? Any tips or suggestions or things I'm forgetting would be greatly appreciated.
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Old 04-30-2020, 09:35 PM
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waterlogged882 waterlogged882 is offline
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Originally Posted by Dtgorrell View Post
Okay guys, Its finally time to drop in a new short block in the 91' prostar190. I posted awhile back about having water in the oil and ended up finding a huge crack in the lifter valley. Since then I've disassembled everything I can with the engine still bolted down. Heads have been removed and gone through, exhaust manifolds, intake manifold, alternator, starter, water pump, timing cover, wiring, etc etc. Alternator and starter checked out good. I've ordered all new gaskets, carb renew kit for the 4160, oil pressure sending unit because I snapped it off. I have everything disconnected and ready to pull this weekend. I'll be ordering a 351w short block from rapido marine in the next week or so, wanna make sure I have all my ducks in a row when it gets here. I've never pulled a boat engine, but I assume once the bell housing bolts and mounts are loose it should lift right out? Any tips or suggestions or things I'm forgetting would be greatly appreciated.
I'd unbolt the engine mounts from the block (front) and the transmission (rear). Leave them attached the hull (if possible). Disconnect the shaft from the transmission and lift the engine and transmission at the same time. Then consider rebuilding the transmission while it is out. New engine...? New transmission...! No better time... also install a dripless seal system and new cutlass bearings in the strut while you're there.

Once the engine is out, make double sure the engine mounts move in both vertical and horizontal directions. If frozen or likely seized, you'll need new one(s) to be able to re-align the engine properly. I have found it easier and as economical to order a new mount assembly in lieu of trying to piece in parts for any one or more mounts.

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Old 04-30-2020, 09:43 PM
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Fullpass Fullpass is offline
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I pull motor and tans at the same time…block/trans bolted together…take plenty of pics to help put things back together, I would also label zip lock bags and put a few bolts in each bag and label.
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Old 04-30-2020, 09:47 PM
Dtgorrell Dtgorrell is offline
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Originally Posted by waterlogged882 View Post
I'd unbolt the engine mounts from the block (front) and the transmission (rear). Leave them attached the hull (if possible). Disconnect the shaft from the transmission and lift the engine and transmission at the same time. Then consider rebuilding the transmission while it is out. New engine...? New transmission...! No better time... also install a dripless seal system and new cutlass bearings in the strut while you're there.

Once the engine is out, make double sure the engine mounts move in both vertical and horizontal directions. If frozen or likely seized, you'll need new one(s) to be able to re-align the engine properly. I have found it easier and as economical to order a new mount assembly in lieu of trying to piece in parts for any one or more mounts.

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The trans was rebuilt less than 2 years ago, has less than 100 hours on it. The motor mounts look clean and new and move without issue, I already tested to be sure. I was really hoping to only pull the engine, just didn't know how hard it is to separate?
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Old 04-30-2020, 09:49 PM
Dtgorrell Dtgorrell is offline
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Originally Posted by Fullpass View Post
I pull motor and tans at the same time…block/trans bolted together…take plenty of pics to help put things back together, I would also label zip lock bags and put a few bolts in each bag and label.
Thanks for the tips! I'd really like to leave the trans alone. I've taken plenty of pics already, and every bolt or small part is in a labeled bag
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Old 05-01-2020, 05:13 AM
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The way you want to do it, engine only, will be separating the engine from the trans spline that fits up into the the damper plate, so you will half to support the the trans when doing this, push the motor forward off the spline when removing, which is doable, the hard part will be getting the motor back in the boat and aligning the damper plate with the transmission spline, motor is on an angle, just makes things harder for you…You asked, guess you will find out…kids can only tell them, they will just half to figure it out themselves…said in kindness…There will be some guide pins to help bolt things back up, just be careful while threading trans bolts back into the block, if you try pulling motor back to trans with the bolt threads, you could strip the bolt threads…so much easier to mate the transmission to the block and not the block to the transmission, trans is light and more maneuverable to align/mate the transmission to the block…so now said it twice...
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Old 05-01-2020, 07:02 AM
Dtgorrell Dtgorrell is offline
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Originally Posted by Fullpass View Post
The way you want to do it, engine only, will be separating the engine from the trans spline that fits up into the the damper plate, so you will half to support the the trans when doing this, push the motor forward off the spline when removing, which is doable, the hard part will be getting the motor back in the boat and aligning the damper plate with the transmission spline, motor is on an angle, just makes things harder for you…You asked, guess you will find out…kids can only tell them, they will just half to figure it out themselves…said in kindness…There will be some guide pins to help bolt things back up, just be careful while threading trans bolts back into the block, if you try pulling motor back to trans with the bolt threads, you could strip the bolt threads…so much easier to mate the transmission to the block and not the block to the transmission, trans is light and more maneuverable to align/mate the transmission to the block…so now said it twice...
I appreciate the advice. If I do pull the trans what more is involved? The cooler lines and unhook the driveshaft? I've not looked at it in depth, but I'm sure I can figure it out if need be. I don't mean to argue with guys likely much more knowledgeable than me, I just want to I cross every T and dot every I to make this as smooth a process as possible.
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Old 05-01-2020, 08:07 AM
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waterlogged882 waterlogged882 is offline
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Originally Posted by Dtgorrell View Post
I appreciate the advice. If I do pull the trans what more is involved? The cooler lines and unhook the driveshaft? I've not looked at it in depth, but I'm sure I can figure it out if need be. I don't mean to argue with guys likely much more knowledgeable than me, I just want to I cross every T and dot every I to make this as smooth a process as possible.
To lift the entire assembly, your shaft coupler has to be disconnected, engine mounts (obviously), hot and ground battery cables, fuel line from the pump or from the filter (I prefer the filter side of the fuel line), exhaust hoses, water hose from the hull inlet, and the wiring harness.

There is a plug on the wiring harness that allows quick disconnect near the starboard side rear of the engine. It may be under a cover but it's there. Pull it apart, done deal for that.

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Everything else is self-contained with the engine and transmission. Transmission cooler lines can stay in tact. You'll need to remove the water intake hose from the now stern-side of the cooler in its horizontal position and from the hull's intake port. To me, easier than removing the cooler lines. Read on down for a tip I have found for repositioning the cooler and you can plan now for that later if you so choose.

Fullpass is spot on with directions. He knows much more than I do about engines.

Again, I recommend lifting the entire assembly and do the separation work outside the boat (as well as reassembly).

Same thing when you set the new engine in...it all goes in much easier when re-fitting the whole assembly instead of aligning components in the boat.

While you're there make sure you have the oil change hose connected to the oil pan for easy oil changes. I think the 91 model has that feature but just make sure. No better time than now.

You may know this but I'll say it anyway: when you set the new engine and get it on the mounts, etc.... as you set the engine remember that you will be setting the engine to connect and align the shaft coupling to transmission coupling. Therefore you want the shaft in place (fairly well centered in the hull opening). Do not set the engine in and then figure on pulling the shaft in one direction or the other toward the engine position. Read that again...set the engine to align with the shaft, not the shaft to the engine. Otherwise and you'll be re-aligning everything to get the vibration out.

Again, if it works, leave the mounts on the boat and disconnect them at the engine and transmission. Why? 1) one less risk of dealing with stripping a connection that MC did a poor job of using a threaded insert or lag, whichever the 91 has, and 2) the re-positioning of the new engine may get you close to the original engine position for maybe a little less work toward proper alignment. No guarantees. It you want them out and out of the way, then by all mans take them out. I have seen a lot of connections for engine mount, fuel filters (which you should relocate while you have easy access) and bilge blower brackets that create headaches.

I moved my fuel filter to the rear next to the fuel cell (port side) and moved the battery up front.

Another consideration and something I prefer for running the boat in the driveway; When you put the engine back in and hook up the water intake to the raw water pump, re-plumb your hose to allow the transmission cooler to be mounted vertical and attached to one bolt on the bell housing. I think it now lies horizontal and near the floor on the 91 model. Turn it up vertical and you will have much easier access to the intake side (now on top) of the cooler to inspect and clean out any debris blockage, and also you can easily water the boat from a garden hose easily through the top of the cooler. That small modification is a game changer for those two advantages. For anyone wondering (91-94 era) this will not work on the 94 Chevrolet setup. Not enough room in that area to go vertical.

No need to disconnect any of the transmission fluid hoses. There is enough hose and room as it is now to turn the cooler up 90 degrees to vertical .

Moving the fuel filter off the stringer and back onto the rear panel also makes changing that filter a breeze in lieu of the dreaded chore.

No better time than now and that is an easy peasy project.

$0.02

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Last edited by waterlogged882; 05-01-2020 at 09:51 PM.
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Old 05-01-2020, 09:14 AM
Dtgorrell Dtgorrell is offline
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Boat: 1991 mastercraft prostar190 351w
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Awesome directions! Thank you so much! I have everything disconnected except the trans coupler. Are you referring to directly on the back of the transmission? Or the assemble down farther on the shaft. It looks like it comes apart there also. I planned on leaving the mounts attached to the hull, and if possible not move the adjustments at all in hopes the new one will set right in. I'm pretty confident on removal and replacement, assembly etc. The only thing I'm worried about is getting the timing correct once its time to start up, thats one thing ive never done. I set the engine to tdc and made marks on the prestolite before I removed it. But I'm really thinking about converting to electronic ignition. I've read some good right ups here about it. But still nervous about it, don't want to fry a new engine. Again thanks for all the help!!
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Old 05-01-2020, 10:01 AM
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waterlogged882 waterlogged882 is offline
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Quote:
Originally Posted by Dtgorrell View Post
Awesome directions! Thank you so much! I have everything disconnected except the trans coupler. Are you referring to directly on the back of the transmission? Or the assemble down farther on the shaft. It looks like it comes apart there also. I planned on leaving the mounts attached to the hull, and if possible not move the adjustments at all in hopes the new one will set right in. I'm pretty confident on removal and replacement, assembly etc. The only thing I'm worried about is getting the timing correct once its time to start up, thats one thing ive never done. I set the engine to tdc and made marks on the prestolite before I removed it. But I'm really thinking about converting to electronic ignition. I've read some good right ups here about it. But still nervous about it, don't want to fry a new engine. Again thanks for all the help!!
You will see a stainless coupling with two flanges, one on the shaft the other on the transmission. Four bolts. That is where you'll disconnect.

I would have thought your 91 has the electronic ignition. Double check by lifting the distributor cap and see if there are a set of points or an electronic module under the rotor.

If you do not have the EI, a conversion kit is readily available and easily installed.

Timing is a breeze. You'll need a timing light and a few basic tools (wrench, screwdriver).

Plenty of tutorials here on setting timing or plenty of knowledgeable folks that can assist.

On the engine alignment, you may get close but you're looking for +0.003" / -0.00" gap for a good alignment. That too is easy enough with a little patience.

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