Gen V to Mark IV Swap - Sea Water Pump Changeover

[FuelishBehavior]

I currently have a 1993 Crownline, 225 CCR with a Gen V 7.4L Bravo 1. It has met it's doom. I have a new custom built 550 HP 496 stroker to replace the old girl that utilized a Mark IV block in lieu of the Gen V. With that being said, I want to use the 1988-1991 Mark IV sea water pump WITHOUT the fuel pump provision (cheaper) since I can now use the engine block provision for the fuel pump. Does anyone have a picture/diagram of how the 88-91 sea water pump bracketry mounts to the passenger side of the engine because it is different than the Gen V and also doesn't require the idler pulley either?

I also realize that the oil adapter for the remote oil filter is a bit different but that is straightforward. Are there any other items I should concern myself with that might require different parts.

 

[alldodge]

The idler pulley is an easier setup IMO but folks like tpenfield has what your wanting to install. The one with the fuel pump option on the pump can also just add a cover plate and continue to use

 

[FuelishBehavior]

Its just that the 88-91 sea water pump is HALF the cost of the one I have now on the existing Gen V engine. Can you explain why in your opinion the idler setup is easier? Just curious.

 

[alldodge]

Its just that the 88-91 sea water pump is HALF the cost of the one I have now on the existing Gen V engine. Can you explain why in your opinion the idler setup is easier? Just curious.

To remove or install the pump without the idler, bolts are removed or added, the belt cannot be removed until bolts are removed. The belt is placed on the pulley, then it needs to be moved into position an bolts tightened. If the belt gets loose, it gets replaced, it cannot be retightened. A pump with the idler, the belt is tightened after the pump is installed.

 

[FuelishBehavior]

I see. Let me ask you this then. Will the '88-'91 sea water pump fit in the '93+ bracket then? This would allow me to use the idler as well as the cheaper pump.

 

[alldodge]

Yes, the pump and the bolt pattern are the same. Either pump will mount, so long as you have room.

The 496 models came with serpentine belt systems, but your using V-belts

 

[FuelishBehavior]

This isn't a Gen VII Merc 496. This is Mark IV 496 stroker. Basically just a 454 bored .060 over with a 4.25" crankshaft. I like the idea of bolting the cheaper pump onto the Gen V bracket and using the idler then! That's a great solution.

 

[Scott Danforth]

I currently have a 1993 Crownline, 225 CCR with a Gen V 7.4L Bravo 1. It has met it's doom. I have a new custom built 550 HP 496 stroker to replace the old girl that utilized a Mark IV block in lieu of the Gen V. With that being said, I want to use the 1988-1991 Mark IV sea water pump WITHOUT the fuel pump provision (cheaper) since I can now use the engine block provision for the fuel pump. Does anyone have a picture/diagram of how the 88-91 sea water pump bracketry mounts to the passenger side of the engine because it is different than the Gen V and also doesn't require the idler pulley either?

I also realize that the oil adapter for the remote oil filter is a bit different but that is straightforward. Are there any other items I should concern myself with that might require different parts.

make sure your adapter block has the correct setup for the block oiling system. the Gen V and VI block have much better oiling than the Mark IV block (Ge V and VI are priority main oiling). the bypass check valve settings are different

Yes, the pump and the bolt pattern are the same. Either pump will mount, so long as you have room.

The 496 models came with serpentine belt systems, but your using V-belts

He is using a Mark IV 454 block with a 4.31 bore and a 4.25 stroke and not the Gen VII 8.1 liter (also 496 cubes) which was a 4.25" bore and a 4.375" stroke)

the Mark IV stuff was all v-belt (think 1990 and prior)

 

[FuelishBehavior]

Scott, if I just use adapter that connects to the engine filter boss on the 88-91 Mark IV engines I should be ok correct? The bypass valve is inside the adapter I believe? I know the Gen V and VI blocks are flush at the filter boss which requires a different adapter and the Mark IV has a recession where the adapter fits up into this area. I'd hate to fry my new stroker!

 

[tpenfield]

I've had both Mark IV and Gen5/6 blocks in my day. The sea water pump bracket for the Mark IV setup is a simple hanger with a secondary tensioner bracket.

Mercruiser Part numbers 15295T (Hanger) and 15751T ( Tensioner)



the fuel pump is the simple engine block mounting type. Mercruiser part 862048A1, which is a Carter M60601 pump.

 

[alldodge]

This isn't a Gen VII Merc 496. This is Mark IV 496 stroker. Basically just a 454 bored .060 over with a 4.25" crankshaft. I like the idea of bolting the cheaper pump onto the Gen V bracket and using the idler then! That's a great solution.

That clears things up, you have a bored out 454, could have figured it out but wasn't paying any attention to the Gen of the block only the 496 statement

 

[Scott Danforth]

Scott, if I just use adapter that connects to the engine filter boss on the 88-91 Mark IV engines I should be ok correct? The bypass valve is inside the adapter I believe? I know the Gen V and VI blocks are flush at the filter boss which requires a different adapter and the Mark IV has a recession where the adapter fits up into this area. I'd hate to fry my new stroker!

you have to know what bypass is installed in the block. the adapter is just a hunk of aluminum. you should search out big block oiling (Grumpy Jenkins does a bunch of write ups on it)

your gen V had a 30# bypass installed in the block vs the standard 11# one for use with the standard Mercruiser oil filter adapter. I couldnt tell you what needs to go into a Mark IV

 

[FuelishBehavior]

Are you referring to the small valve, part no. 6? I would think if you use the entire adapter and valve I would be good to go, the only other bypass would be in the oil pump itself. All that is in the block are galleries and passages. I don't think there are bypass valves built into the block with ratings on them but I could be mistaken.

 

[Scott Danforth]

nope, Im talking about the oil filter bypass check valve about 2" up in the block from the filter boss. what was your block assembled with?

Item 6 is the bypass that is added to the mercruiser adapter by mercruiser.