Replacement engine turned around to work with a V-drive?

Geoffrey Wallington

Geoffrey Wallington

Member
Dec 23, 2020
45
Norfolk, VA
Boat Info
1999 330 Sundancer
Engines
Tein Mercury 7.4L - 454 Cu. Inch
We have to replace our port failed 454 Mercruiser with a different engine because they are not made anymore. The mechanic says he can buy a standard engine and just flip it around. Is this possible? my pervious engines were left hand turning. The propellers were inward turning. If the new engine is a left hand turning engine that he has to turn around, won't that screw up the rotation of the propellers? He says there are no v-drive 8 cylinder engines on the market and that turning this one around is not a big deal. Is it or not? What about gear selector? Won't selecting forward put the propeller in reverse and vice versa?
 
If the blown engine is counter rotation the replacement needs to be also. It mates to a counter rotation trans.

A non counter rotation engine can be converted if that is what is meant by “flip it around”?

Counter rotation engines use a different cam and water circulation pump.
 
Both engines rotate counter clockwise. Left hand. The new mercruiser is also CCW, left hand turn. but I guess it is not a V drive engine. It is meant to face forward. The mechanic says all he has to do is turn the engine around so it faces backwards, then swap the exhaust manifolds so they go out over the front of the engine, which is now towards the stern.
 
The exhaust manifolds are generally the same left to right so only the risers need to be turned around. I strongly recommend using Mercury riser gaskets as they are much better sealing than the off brands.
The oil pump and oil pan are standard so unless the installed engine is in a position where the front is lower then the rear (which I have never seen) you will be fine “flipping” the engine around.
 
Wanderer 290 said:
The exhaust manifolds are generally the same left to right so only the risers need to be turned around. I strongly recommend using Mercury riser gaskets as they are much better sealing than the off brands.
The oil pump and oil pan are standard so unless the installed engine is in a position where the front is lower then the rear (which I have never seen) you will be fine “flipping” the engine around.
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Thanks Wanderer. I hope so! I'll post an update on how it goes
 
I did a quick search and those engines are still available. Try googling remanufactured 7.4 marine engines. www.ebasicpower.com
 
We looked at this. However, the engine is being replaced through an insurance claim. The mechanic says it is better to have a new engine than a rebuilt one, even if the two motors are different, when it comes to resale value. Also, he thinks the ECM has failed and he says he can't find a replacement ECM, so rebuilding the motor is not an option.
 
What is he replacing it with? A rebuilt orignal could be perfectly fine, I consitent with other discussion on this site, the insurance company may not be willing to pay for a new engine. Are they?
 
The mechanic estimate quote said he could not repair the current engine. Quoted 8.1 496 Mercruiser complete engine $25550. Insurance company approved it.
 
$25k. You cannot possibly be serious. Right now i looked up a reman 7.4 MPI. $4,652.
I re-read about the left engine, i not a mechanic but i would think any engine can be made to turn CC or CCW. Engine is an engine, nothing special abourt the port one.
 
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So you are going to have a mismatched set of engines? An 8.1 on one side and a 7.4 on the other? Well, you just killed your resale value. No way I would ever consider a mismatched engine room. Not a chance.

The vDrive transmissions can be run in forward or reverse to change the rotation to what you want. IN fact that is how most are set up. Both engines run the normal rotation and the transmissions are set up with one running in “reverse” so the props counter rotate.

If it was me, I would source a remanufactured 7.4 from a reputable builder before I would put an 8.1 in. Or, actually, if you really love the boat, you might consider selling your good 7.4 and putting in a pair of 8.1s matched properly. SInce the 7.4s seem to be in short supply, you would probably get good money for it. THen you would have added value to your boat with a brand new set of 8.1s.
 
Creekwood said:
So you are going to have a mismatched set of engines? An 8.1 on one side and a 7.4 on the other? Well, you just killed your resale value. No way I would ever consider a mismatched engine room. Not a chance.

The vDrive transmissions can be run in forward or reverse to change the rotation to what you want. IN fact that is how most are set up. Both engines run the normal rotation and the transmissions are set up with one running in “reverse” so the props counter rotate.

If it was me, I would source a remanufactured 7.4 from a reputable builder before I would put an 8.1 in. Or, actually, if you really love the boat, you might consider selling your good 7.4 and putting in a pair of 8.1s matched properly. SInce the 7.4s seem to be in short supply, you would probably get good money for it. THen you would have added value to your boat with a brand new set of 8.1s.
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I agree. Two mismatched engines are a no go for me as well. You're going to be fighting with mismatched everythign -- props, rpms, HP, torque curves, fuel usage. etc.
 
Insurance approved 25k? well that's something I didn't think I'd ever hear. So putting that into the mix how do you get to where you're left with a boat that is at it's best. I agree that mixed matched is a terrible idea. The insurance probably says they'll pay for one engine and you'd have to pay for the other one. I think the boat would be a rocket with 8.1's but I've seen that boat with 5.7's & 6.2's so why not ask about those options and maybe you can end up with two new engines in the end?
 
The mechanic says the issue is that changing to a smaller engine would need to change the transmissions so that I would get the torque required to get up on plane. A gear ratio problem. He says he has done this on numerous cruisers successfully.
 
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