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wtrskiscout

Motor- Upgrading to EFI

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wtrskiscout

I don't know if this has been covered here.

We have an 1988 Sunsetter with a bad motor. Threw a rod, broke camshaft.

We are considering buying a used Mercruiser Magnum to replace it.

Has anyone done this? Will the motor fit under the doghouse? Any other considerations?

I hope this is the right place to post a question like this? All advice appreciated.

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Woodski

The engine will certainly fit. The key will be to ensure that if you change them, the ancillaries all fit. Those will include the exhaust manifolds and elbows, intake manifold and carb or throttle body & spark arrestor, the alternator, etc. From a long block engine configuration, it will be identical to what you are removing.

If you are switching from a carb to fuel injection, there will be several items you will need to procure or ensure you have. Wiring harness, ECM, proper fuel pump, lines, return plumbing all could or will be required depending on what type of injection system you are installing.

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wtrskiscout

Woodski,

Thanks for the reply. I know the motors are basically the same. Your points about the different fuel pump, wiring harness, etc are what I was trying to get info on.

How about anybody doing an aftermarket efi conversion of a carbed motor?

Obviously just putting a complete Mercruiser factory efi motor in place of my Merc carb motor would be easiest.

Anyone who has done this would be a great resource to me.

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Woodski

Edelbrock and Holley offer EFI conversion kits for small block V8's. They come complete with all required parts and look to cost around $2k. Some of them allow you to alter some of the calibration on them so they can be tuned to your liking. The one thing that you can not do is use an O2 sensor (because they can't get that wet and read mixture), so that is something that you need to be aware of when considering your options. Their respective websites have information on them.

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Michigan boarder

Just curious, how many hours were on the engine? Do you know how well it was cared for since 1988? There is a thread going on this site right now about how long an engine lasts.

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wtrskiscout

MI Boarder,

The motor is the original motor from the 88 sunsetter. It has 632 hours on it. Previous owner said he forgot to drain motor pre-winter and first time out last spring the motor blew.

After removing the motor it is a little difficult to assertain exactly what happened, but seeing the broken connecting rod makes me think maybe some water got in the combustion chamber and caused the failure. The broken rod caused some more damage like the snapped camshaft. The motor still does turn freely.

I don't know how this info fits into the study of how long a motor should last. There appears to be very little wear on the internals besides the failed parts.

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Michigan boarder

MI Boarder,

The motor is the original motor from the 88 sunsetter. It has 632 hours on it. Previous owner said he forgot to drain motor pre-winter and first time out last spring the motor blew.

After removing the motor it is a little difficult to assertain exactly what happened, but seeing the broken connecting rod makes me think maybe some water got in the combustion chamber and caused the failure. The broken rod caused some more damage like the snapped camshaft. The motor still does turn freely.

I don't know how this info fits into the study of how long a motor should last. There appears to be very little wear on the internals besides the failed parts.

No, you're right, it doesn't play much into the study. I was just curious, for example if you said it had 2200 hours and one day coming out of the hole, POW!, it flew apart, then that could be noteworthy. But as far as the thread goes, everything points to good maintenance and they last forever, and it sounds like the previous owner missed a step and cost him an engine.

Thanks for the info, and good luck with the conversion. Outta be a heck of a boat when complete.

Edited by Michigan boarder

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Woodski

I would certainly consider rebuilding the existing mill assuming there are not other damaged parts, specifically the block as water left in them usually means a crack somewhere. Sounds like there are at least 7 good pistons and rods. If nothing else, you could do a cost study on pros and cons to each of your options. If you want to invest some $$, I would suggest looking at the heads, the newer (post '96) Vortec style heads used on small block GM engines flow a significantly greater amount of air than the earlier ones. There are many options for that upgrade from GM and several aftermarket vendors. If you go the rebuilt route, one key ingredient will be your camshaft, the marine cam is different than a road car camshaft. You should go to the GM Performance Parts website and/or get a parts catalog to do some research on components.

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footnlongline

If the replacement motor is a used EFI merc, what is it, throttle body or MPI? What boat is the replacement motor out of? If it was a Bu, maybe you can get them to throw in the wiring harness as well. If you can do this the swap will be fairly straight forward. Now would be a good time to replace the exhaust manifolds and risers if they were original on either motors, raw water pump, hoses etc. should be replaced.

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wtrskiscout

Haven't found a replacement block yet. Probably won't rebuild this one because of the possibility of being cracked. Replacement blocks are easy to find and putting the marine parts on it isn't too hard. Cam has to be new as ours is snapped, so that is a wash also.

Footlong mentioned that the exhaust manifolds and risers may need to be replaced. What goes bad with the manifolds? What should I look for?

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footnlongline

Haven't found a replacement block yet. Probably won't rebuild this one because of the possibility of being cracked. Replacement blocks are easy to find and putting the marine parts on it isn't too hard. Cam has to be new as ours is snapped, so that is a wash also.

Footlong mentioned that the exhaust manifolds and risers may need to be replaced. What goes bad with the manifolds? What should I look for?

They rust through and cause water to run back into the engine at idle. You cant tell if they are bad by looking at the outside of them. Mine rusted through and I had to replace my motor because of it, it is a long story so I won't bother you with it but I got a quick silver re-man with a warranty.

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