Engine conversion - Is it doable?

Talon92

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Mar 2, 2021
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Hello everyone! Would like some help from all of you with experience - I have an 84 21' Cuddy Cabin Invader with a Volvo Penta 260 outdrive attached to a 5.0 GM carburated motor that sustained a 2x block cracks while in Afghanistan - not properly winterized..... boat is in great shape and has sentimental value and would like to keep it....would like to replace the old carburated motor with a newer Fuel Injected of same or slightly higher HP. Is it doable and what are the technical considerations? Any suggestions or recommendations for a good place to buy good, reliable and reasonable marine engines? Thank you.
 

Bondo

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Apr 17, 2002
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Ayuh,...... Welcome Aboard,....... Easy Peasy,.....
Though, the switch to Efi will add several thousand dollars to the task,.....

I'd recommend ya go with a pair of late model 350s, 'n 4bbl. carbs,.....
 

Scott06

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Apr 20, 2014
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Try michigan motorz https://www.michiganmotorz.com/products/marine-engines

you can scroll through the options from rebuilt long blocks to the complete injected engine you seek. If you buy a complete turnkey injected engine it will be a relatively drop in job. your budget will determine the best path forward. as Bobdo mentioned good time to upgrade to 5.7/350
 
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Scott Danforth

Grumpy Vintage Moderator still playing with boats
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fuel injection does not get you any more power or fuel economy than a carburetor. it just costs a lot more.

later model Gen 1 GM motors are simply running Vortec heads
the latest models of motors are either LS series or LT series with variable valve timing

recommend you go with a pair of 350's like bondo said. or upgrade the drives to at least VP290's or DP-A's and run 6.2 liter strokers
 

jerryjerry05

Supreme Mariner
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May 7, 2008
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17,923
Looks like he's running a single and putting twin
anything would be a huge job!!! :)
You'll need to do a lot of research as to what will
bolt up to your drive.
Or find a complete motor/drive system or change to
Mercruiser.
 

alldodge

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Is it doable

Yes its doable, just cost more money. The new motor comes self contained and will require new wiring harness up to the helm and may need to change the gauges to a monitor display. All depends on which you choose
 

Lou C

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Nov 10, 2002
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11,798
Your best bet is to find out what rear main seal/flywheel design will work with your present Volvo drive and get a reman V8 that will work with that. As far as EFI vs carb I vote for carb, lower initial cost much lower repair cost no added wiring etc. Keep in mind people with older Merc or Volvo EFI systems have gotten burned by these companies making certain critical EFI parts NLA. With a simple carb (Edelbrock or Holley both can be bought brand new with spare parts everywhere) and a mechanical or low pressure electric aftermarket pump that will not happen. Just my opinion.
 

kenny nunez

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Jun 20, 2017
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3,056
For just over 6k you can get a brand new 5.7 marine engine with manifolds that will have all the attaching locations your current engine has which will be a slam dunk. Check out Marine Power in Pontchtoula La. They have dealers around the country which may be near your location.
PS, Thanks for your service.
 
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