Dropping a newer engine into an older boat

AKveps

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Apr 28, 2012
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I have a 1981 28 ft Bayliner Victoria Sunbridge with a standard GMC 5.7L carbureted engine with fresh water cooling.

The engine is tired and burns a fair amount of oil.
The engine is flanged up to an AQ280 with a Duoprop


I have the opportunity to pick up a used (300 hr) newer MPI 5.7L
The engine is complete with everything still attached (exhaust manifolds, alternator, electronics, hydraulic pump, etc)
It was originally flanged up to a DP-SM Drive unit

The engine is a 5.7 GI-E

I believe it was pulled out of a 2000

My question is, how difficult would this upgrade be to pull off?
Is it a fairly ease upgrade or is there a lot to it that would need to be changed, if its even possible?

For instance, specifically:
Will my exhaust manifolds from my present engine bolt onto the new engine
Or will the new exhaust manifolds flange up to the exhaust yoke on the 280
Does the new one have electronic throttle control or is it standard cables?
I don't have any use for the hydraulic pump, so what's the best way to deal with this?
Will the motor mounts drop into the same place on my motor blocks?
Electrically is it difficult to hook up?

Would I see much of an advantage with this engine over a rebuild of the present engine in the boat?


I'm looking for any input from anyone who may have gone down this path to steer me clear of it or tell me its a great way to go.

I like the idea of the MPI for ease of starting, but I'm open to suggestions.

Thanks for any insights or suggestions.
 

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alldodge

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A 5.7 is a 5.7 is a 5.7.... The block is the same, the motor mounts are the same. No need to replace the exhaust unless the new style will not fit your boat, and if that is the case then your old style will fit. Looks like the engine has a new paint job which would make me a bit leery. Don't like the distributer, they have a lot of problems with the "carb" cap style caps. Electrical hook up should not be an issue, it's plug and play. Don't know if it has electronic throttle control, look for solenoids on the throttle linkage. If there is no solenoids then no electric control
 

AKveps

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Thanks for the great info AllDodge.

Good info on the distributor and the electric control. I will find out more about if there are solenoids on the system.
Agreed on the new paint job. Makes me leery also.

Is there anything I should ask them to report out of the engine control module to let me know how it was handled?

I was talking to another source that indicated the heads may have a different bolt pattern than the 1981 5.7 and therefore I couldn't swap in my old manifolds.
My only concern here is that if the manifold exhaust does not line up with the yoke then I would be out of luck.

Overall, would you say this is a large improvement over a straight carbureted model? Purchasing this used engine will cost me probably $2-3K over a straight carbureted rebuild, which may be worth it if its a drop in, but not if there is a lot of modding to get it to fit...
 

jerryjerry05

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The exhaust can be adapted to fit.
A piece of hose and an elbow.
The new bell housing will need to be taken off and the flexplate used and the old bell housing needs to be used.
If these fit then try.
If the flexplate won't fit then possible the old flywheel can be transferred.
The 5.7 is not the same 5.7 you have.

Since you have FWC on the old motor you can still buy a crate motor and put it right in.
Otherwise the freeze plugs and headgaskets would need to be changed.

OR!!! You can change out the whole setup with the newer drive and have power trim.
 

AKveps

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Thanks again
I pulled the trigger on a Gxi-F 5.7. (2004-2005)
The flywheel on the new engine is the 14" and my original flywheel is the 12.75"
Can I just use my old one or is there a balancing issue?
The exhaust manifolds on the new engine will not line up to the exhaust yoke, so I'm going to use the original manifolds
However, I will need to drill some holes in them to mount the temperature sensors that are on the news engine. Any suggestions?


Don suggested on another post that the easiest way to bypass the hydraulic pum is TI tie the lines together
I'm wondering if this will cause the pump to overheat without any water cooling or should the hydraulic line heat exchanger be left in?
Was there ever a similar engine built without a hydraulic pump that I could use for the right parts?

Lots of questions and thanks for the help
Anyone with this kind of experience?
 

jerryjerry05

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That 5.7GIE is about 8-9 years newer than you said.
The manifolds probably won't swap.
The flywheel is balanced but won't fit.
The earlier cranks have a different end and won't match for the flywheel to mount to.
The early v-8 used a light duty truck engine and a flywheel from a Camaro v-6.
The bell housing probably won't swap either.
The power steering pump was used in some cases on the older motors but that was using the V-belts.
To just hook the lines together wouldn't be a problem but the oil cooler isn't hard to put in the system..

If the drive and transom assy. is available? You'd be way better off to buy that too.
 

Bondo

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Thanks again
I pulled the trigger on a Gxi-F 5.7. (2004-2005)
The flywheel on the new engine is the 14" and my original flywheel is the 12.75"
Can I just use my old one or is there a balancing issue?

The exhaust manifolds on the new engine will not line up to the exhaust yoke, so I'm going to use the original manifolds
However, I will need to drill some holes in them to mount the temperature sensors that are on the news engine. Any suggestions?


Don suggested on another post that the easiest way to bypass the hydraulic pum is TI tie the lines together
I'm wondering if this will cause the pump to overheat without any water cooling or should the hydraulic line heat exchanger be left in?
Was there ever a similar engine built without a hydraulic pump that I could use for the right parts?

Lots of questions and thanks for the help
Anyone with this kind of experience?

Ayuh,..... Chevy has used both the 153 tooth 12" flywheel, 'n the 168 tooth 14" flywheel,....

Is yer block drilled, 'n tapped to accept the straight across bolt pattern Starter,..??..??
Some are, many ain't,....

Ya can't use the old flywheel, as not only the balance is different, the bolt pattern is also different,...
The old pattern is 3, 1/4", the new is 3",...

If yer block will accept the starter, ya just need a standard V8, 153 tooth, 12" flywheel, for the 1 pc. rear main seal motors,...
 

AKveps

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Apr 28, 2012
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Thanks much for the responses
The drive isn't available so I'm stuck with the drive I have
I will check out if the bell housing fits and the starter bolt holes
I'll be back with some answers and more questions probably
 

AKveps

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OK, to all, thanks for the info. You basically nailed most of it. Heres what I know (with questions)

1) The block is drilled for an inline starter. Still trying to figure out what the inside starter hole is threaded f. Seems that its different than the staggered starter holes. There was some talk on other sites that the holes may be metric but I havent been able to confirm that - maybe its just junk in the hole.

2) Correct on the flywheel Bondo. Its a 3" hole pattern with 153 teeth and a 12.75" diameter. Built to balance the crank.
On this, is there any concern for balancing the flywheel for the 5200 rpm top end of this engine or will any used flywheel that fits work?
The two correct flywheel part numbers are:
14088646 - 16 pound light version
14088650 - Standard weight
One of the questions that came up was what type of crank was in the engine. Depending upon whether it was a forged or cast crank may effect the flywheel balance. Is there a way to tell with the oil pan on the engine? Any thoughts on the balancing issue?


3) My research suggests that the bellhousing will fit as all the 350 blocks have the same bell housing bolt pattern. We will see when we get a chance to bolt it up

4) The old manifolds fit. (!) So now all that is needed is to drill some holes in them for temperature sensors. There seems to be a good place in the riser with enough meat to bury the sensor in the casting without piercing the water jacket.

5) Still want to ditch the hydraulic pump somehow, but havent found bracketry that would make that easy.

If Im missing anything obvious or not so obvious, feel free to chime in. More to come...
 

Bondo

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Ayuh,.... Starter bolt holes should be 3/8"-16,....
Standard 3/8" course threads, but use the Chevy, or better yet, the Mercruiser starter bolts, which use a 1/2" head, rather than 9/16" head, for better access,...
If they're metric, I believe they're 10mm standard pitch,....
The staggered pattern uses two Long bolts, the straight across, a long, 'n a short bolt,...

#2,.... Use the standard balance, standard weight flywheel,....
Yer motor is considered standard Chevy internally balanced,...

Crank material, is irrevelant, 'n No, ya don't have a forged crank,...
Chevy hasn't put forged cranks in production motors since the 283/ 327s of the 1960s,...

Chevy bellhousin' bolt pattern, is, 'n has always been the Same, atleast since 1955,.....
Anything from the 2.5l/ 3.0l, to the SBCs, to the BBCs, will All bolt to the same flywheel covers,....
The BBCs have one extra bolt hole, top center, that can be left out,...

'n,... Ya might be able to replace the risers, to get the sensor bungs, already in-place,...
 

AKveps

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Apr 28, 2012
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Do you know what the thread size is for the exhaust manifold temperature sensors? I believe the right part number is 3862500
I triad an M10 X 1 into some blank stock and it almost fits, but seems tight.
It looks like the thread pitch is a 28, but that seems wierd
Outside diameter on the sensor is 0.400"

There is a 7/16-28 UNEF, but unfortunately I dont have that one in the shop. Does that seem right?
 

AKveps

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Just an update on the repower.
I put the Gxi-F into the old boat. Looks like the motor I bought was a dud, as it threw a rod bearing in the second hour on the water. The extra hp made quite a difference though. 3/4 throttle (4200 rpm) pushed the boat at about 50 kph. Quite the difference. I would recommend the upgrade to anyone tired of their carbureted motor. The EFI is easy to start and responds really well to throttle.

After the motor packed it in, I had it back in the shop and within the hour had the motor out of the boat.
Now going for a rebuild on this motor and getting it back in the water.

Question on the power steering pump. I tied the intake and output lines directly together (without the inline oil cooler) and found the pump got hot (to hot to touch)fairly quickly.
Has anyone had any luck on deleting the power steering pump completely? I would like it gone or better yet, replaced with a second alternator. Any kits for that or has someone come up with a bracket to do this?
 

mandmj

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I have a gxi-f as well, and I remembered seeing a post from the late Don S. about this same thing. They made a GXiI-F (extra i for inboard) w/o the PS. takes a different bracket which I'm sure will be expensive.
 

Bondo

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Question on the power steering pump. I tied the intake and output lines directly together (without the inline oil cooler) and found the pump got hot (to hot to touch)fairly quickly.
Has anyone had any luck on deleting the power steering pump completely?

Ayuh,.... Hunt down an actuator, 'n cooler, then hook it all up,....

P/S is a pretty easy addition, that makes drivin' Comfortable,.... No prop torque steer,...
 

AKveps

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Thanks for the breadcrumb mandmj.
I found the bracket for a 5.7 without a power steering pump. The Volvo part number is 3863179 and its about $280. Kinda pricy.
If I could find it cheaper I would go that way, but being in Canada, that part landed here is going to be over $400 - ouch

I'm going to try to figure out how to add a second alternator where the power steering pump was or add a second idler.
Seems like a bit of welding on the original bracket should do the trick.
 

mandmj

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well, I don't know if it would work on not, but there is a similar bracket on e bay for 80 bucks. see if the below link works. if not, just e bay search the part number in question. I think the one there is for a big block, but maybe Bondo could tell you if it would work.
 

Bondo

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I found the bracket for a 5.7 without a power steering pump. The Volvo part number is 3863179 and its about $280. Kinda pricy.
If I could find it cheaper I would go that way, but being in Canada, that part landed here is going to be over $400 - ouch

Ayuh,..... A used P/S actuator, 'n cooler would probably cheaper, 'n you could enjoy the ease of steerin',...

I have no idea 'bout the Volvo bracketry,.....
Donno whether the bolt holes on the front of a BBC are the same as a SBC, just know the aft bolt holes are,....
 

AKveps

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Thanks again mandmj. I sent a message to the seller to see if he can get me a part number on it.
Thanks also for the suggestion Bondo, I will look into that also.
Your right, it may be quicker. I have the cooler. What does the PS actuator look like? Do I need to change anything else on the steering?
 

AKveps

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Bondo,
I stuck with the power steering pump ( I couldn't find a power steering pump delete style bracket).
I also have the cooler.

What does the actuator look like for my old boat?
Is it easy to install or is there a lot of cable replacements or such that I have to do?
 

Bondo

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What does the actuator look like for my old boat?

Ayuh,.... I don't know That,... But, other than hose/ line hook ups, they all appears to be exactly the same, Merc. Volvo, or OMC,....
 
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