5.0L Mercruiser Swap Question

[Saebin333]

Hi everyone, I'm new to the forum and need some big time help on making sure I pick the right engine to perform a poor mans engine swap.

I currently have a 95' Bayliner Capri 2050LS with a Mercruiser 5.0L engine. This engine has a cracked block and I need to replace it for as cheap as possibe and have it last for AT LEAST this season. I'd run it until it dies and then buy a new refurbished engine once it does.

Long story short, I bought the boat used and found out later that the oil was milky white. I'm pretty sure it was due to improper winterization but the seller would say otherwise. Trust me, I almost caught a charge because of this idiot but now I just try to leave it at a lesson learned.

Either way, my plan is to go to a salvage yard or find a running Chevy 305 from a car/truck and then use that engine to replace the one in the boat. Now I know that it will need brass freeze plugs and marine grade gaskets and seals but what I don't know is what years can i play with for the swap. I'd like to find a replacement that was a 95' but my search so far has shown to be pretty difficult. What year engines can I use to replace it? I know its has a 1 bolt rear main seal and a mechanical fuel pump. To convert it to a electronic fuel pump (depending on the replacement I find) isn't hard at all from what I hear but I wanna make sure the right engine is used with minimal parts needed besides what I already have on the boat now in good condition minus the block.

I know a lot of you would tell me not to use a car/truck motor because of the cams and so-on but like a said, it just needs to run for the season and it'll be replaced next year. I've hear both sides of the issue and some people say I'll be fine and could possibly get more than just 1 season out of it and others say that it'll blow up on my before the end of the seaon.

I just need help on knowing what years I can play with and is there anything special I need to worry about for running it in fresh water only.

Sorry so long but I wanted to make sure I included all of my concerns and comments. Details on the current cracked engine are below:

Model: MCM 5.0L
Displacement: 305 CID
Ignition Timing: 8 degrees BTDC
Spark Plugs: AC-MR44T
Engine Rotation: LH
Engine S/N: 0F417977
Transom S/N: 0F468657
Drive S/N: 0F379296

 

[bomar76]

Re: 5.0L Mercruiser Swap Question

Just find an 87 UP SBC (one piece main seal) engine....and I would really look for a 350, same money, and truck would be nice.
It will bolt fight up.

Earlier versions - 1987 to mid 90's -should have a fully machiend mechanical fuel pump boss so you can use your old marine fuel pump.
Swap to brass core plugs, use the carb, distributor, ignition, alternator, circ pump, and ps pump from the old engine.
Leave the head gaskets alone.
Probably will need to use your old intake manifold as most engines you will find will be TBI or MPI.
Bet your exhaust manifolds are junk too.

Do all this, then go boating.

 

[Saebin333]

Re: 5.0L Mercruiser Swap Question

Just find an 87 UP SBC (one piece main seal) engine....and I would really look for a 350, same money, and truck would be nice.
It will bolt fight up.

Earlier versions - 1987 to mid 90's -should have a fully machiend mechanical fuel pump boss so you can use your old marine fuel pump.
Swap to brass core plugs, use the carb, distributor, ignition, alternator, and ps pump from the old engine.
Leave the head gaskets alone.
Probably will need to use your old intake manifold as most engines you will find will be TBI or MPI.
Bet your exhaust manifolds are junk too.

Do all this, then go boating.

If I find a 350 engine, will I have to worry about the pitch of my prop? And what about my Alpha 1 outdrive, will that handle the additional power without issues? Also, I thought that the head gaskets needed to be marine quality? If I don't have to worry about them then great, that'll save me some good money!

As for the exhause manifolds, they seem to be ok but I'm no pro by any means and couldn't really tell you for sure. I just know that visually, they seem to be on the up-and-up.

Thank you for the information and I appreciate anyone elses comments as well.

 

[bomar76]

Re: 5.0L Mercruiser Swap Question

The head gaskets will be fine.
The Alpha drive will handle the 350, there are millions of them rigged that way.
May need to reprop, hard to say.
I originally left swapping circulation pumps of the list, need to do that too.

 

[brendanstl]

Re: 5.0L Mercruiser Swap Question

There's a thread somewhere on here that tells you how to check your exhaust manifolds for cracks using acetone, it might be in the ADULT section.

 

[Saebin333]

Re: 5.0L Mercruiser Swap Question

The head gaskets will be fine.
The Alpha drive will handle the 350, there are millions of them rigged that way.
May need to reprop, hard to say.
I originally left swapping circulation pumps of the list, need to do that too.

Thanks man! I have a coulpe more questions for you. Again, I'm no pro mechanic so hopefully this isn't that dumb of a question. I see a lot of "Long Blocks" and "Short Blocks" for sale. Which one exactly would I be looking for?

Also, is my motor a 1 bolt main with a 1 piece rear seal or what? I've been seeing engines with a 2 main and a 1 piece rear seal and I'm not sure what they're talking about. I figured this would be really important to get right otherwise I would be dealing with problems on the flywheel or something.

 

[bomar76]

Re: 5.0L Mercruiser Swap Question

If you engine is indeed a 1995 (or at least later than 1987) it is a 1 peice rear main seal.
All Mercruiser 305's and 350's are 2 bolt main.

The 1 piece/2 piece referrs to a major design change in the way the oil seal at the rear of the crankshaft is designed.

Any 1987 or later 305 or 350 will bolt right up and all your bits and pieces will work...but again I'd buy one with a fully machined mechanical fuel pump boss.

Long blok = has heads
Short block = no heads

You want one with heads=long block

 

[Saebin333]

Re: 5.0L Mercruiser Swap Question

If you engine is indeed a 1995 (or at least later than 1987) it is a 1 peice rear main seal.
All Mercruiser 305's and 350's are 2 bolt main.

The 1 piece/2 piece referrs to a major design change in the way the oil seal at the rear of the crankshaft is designed.

Any 1987 or later 305 or 350 will bolt right up and all your bits and pieces will work...but again I'd buy one with a fully machined mechanical fuel pump boss.

Long blok = has heads
Short block = no heads

You want one with heads=long block

You're the man! Thanks again and I REALLY appreciate the information. I'm pretty sure you've just answered all of my questions. As long as your info is correct, I should be boating in no time now

If anyone thinks otherwise or has a few more things to add in, please let me know.

 

[Saebin333]

Re: 5.0L Mercruiser Swap Question

If you engine is indeed a 1995 (or at least later than 1987) it is a 1 peice rear main seal.
All Mercruiser 305's and 350's are 2 bolt main.

The 1 piece/2 piece referrs to a major design change in the way the oil seal at the rear of the crankshaft is designed.

Any 1987 or later 305 or 350 will bolt right up and all your bits and pieces will work...but again I'd buy one with a fully machined mechanical fuel pump boss.

Long blok = has heads
Short block = no heads

You want one with heads=long block

Ok, so I've been talking to my brother-in-law who says that if I want the engine to last longer go for the "4 bolt main" and NOT the "2 bolt main". Will I be ok using a 4 bolt with a 1 piece oil seal? Are there any problems I would be creating for myself by doing so?

 

[funk6294]

Re: 5.0L Mercruiser Swap Question

There will be no difference in how it bolts in the boat and only refers to the number of bolts holding the main bearing caps in the block. Your BIL is not entirely correct in this situation. A four bolt main is great if you are going to build high HP motors and drag racing them. And if you can find one for a good deal then great, but for the HP level you are looking at a 2 bolt main will do fine all day long and you will not see any difference in engine life as a result. Also it is more difficult and expensive to find the four bolt main blocks, the two bolts on the other hand are very easy to come by.

 

[180shabah]

Re: 5.0L Mercruiser Swap Question

There is absolutely no problem using a 4 bolt block, the difference is internal.

However - there is no benefit either, you engine will never be spinning faster than 5k, so the extra support just isn't needed.

As bomar has stated above, any truck/van engine is a great swap for marine duty - no cam swap needed.

 

[John_S]

Re: 5.0L Mercruiser Swap Question

All production SBC Mercruiser and believe all OMC/Volvo were 2-bolt mains. If you want to go 4-bolt mains, should not be any issue. The prefered slavage of a truck motor, might have that as a default, anyway. Only thing to check, is the windage tray. Most boat engines have them to prevent oil splashing on crank. The one from your 2 bolt main might not fit the 4 -bolt, if it didn't have one. Minor stuff.

Since you are on a tight budget, recommend tearing down your 305 to find out what is good/bad. Key items would be marine cam, intake, and heads. The heads would need to be checked for cracks. Some intakes have known to freeze crack as well. Lifter valley may be cracked too, and if engine turned over, may have damaged cam. Once you know what is good, you can better plan, get what you need.

While you are on a budget, you might want to consider an upgrade to vortec heads, along with Bomar76's recommendation of a 350.

 

[Saebin333]

Re: 5.0L Mercruiser Swap Question

All production SBC Mercruiser and believe all OMC/Volvo were 2-bolt mains. If you want to go 4-bolt mains, should not be any issue. The prefered slavage of a truck motor, might have that as a default, anyway. Only thing to check, is the windage tray. Most boat engines have them to prevent oil splashing on crank. The one from your 2 bolt main might not fit the 4 -bolt, if it didn't have one. Minor stuff.

Since you are on a tight budget, recommend tearing down your 305 to find out what is good/bad. Key items would be marine cam, intake, and heads. The heads would need to be checked for cracks. Some intakes have known to freeze crack as well. Lifter valley may be cracked too, and if engine turned over, may have damaged cam. Once you know what is good, you can better plan, get what you need.

While you are on a budget, you might want to consider an upgrade to vortec heads, along with Bomar76's recommendation of a 350.

Thank you funk6294, import_John_S and especially bomar76. You guys are giving me more quality answers and support than I imagined getting from this forum. I'm glad my friend recommended coming here for some good answers.

The boat did start and it actually purrs when at idle. Even when giving it some throttle, it sounds strong. I almost put it in the water it sounded so good. I'm just glad I checked the oil before doing so otherwise I would've found out the hard way that water was getting into the oil.

As for the Vortec heads, if I can find them then I would really consider it but I'm just gonna start with finding the 350 first. I wanna try to have the boat water worthy by Memorial Day weekend. If I can find these Vortec heads, will they just bolt right up with nothing more needed? What I mean is, will I have to do anything more than what I would be doing by using the heads from the salvage motor I find?

Seeing how I'm on tight budget, I might just leave everything alone and go for goal of just getting it installed and started!

 

[John_S]

Re: 5.0L Mercruiser Swap Question

As for the Vortec heads, if I can find them then I would really consider it but I'm just gonna start with finding the 350 first. I wanna try to have the boat water worthy by Memorial Day weekend. If I can find these Vortec heads, will they just bolt right up with nothing more needed? What I mean is, will I have to do anything more than what I would be doing by using the heads from the salvage motor I find?

The vortecs will require a different intake, and you would want to go with a 4brl at that point. If your current one freeze cracked on the inside, you will be looking for a new intake anyway.

 

[AZSenza]

Re: 5.0L Mercruiser Swap Question

If you go Vortec heads you'll need a carburetor intake manifold, your pretty limited to after market, price is in the low 100$ range. All Vortecs I know of were fuel injected.

 

[bomar76]

Re: 5.0L Mercruiser Swap Question

Ok, so I've been talking to my brother-in-law who says that if I want the engine to last longer go for the "4 bolt main" and NOT the "2 bolt main". Will I be ok using a 4 bolt with a 1 piece oil seal? Are there any problems I would be creating for myself by doing so?

Tell your brother in law to buy his own boat and do whatever he wants to to it.
Every Mercrusier and Volvo SBC engine based sold is 2 bolt main.

 

[180shabah]

Re: 5.0L Mercruiser Swap Question

Vortec heads would be a great power boost, but given your situation you may want to pass. An intake will add $2-300 to the budget.

 

[bomar76]

Re: 5.0L Mercruiser Swap Question

As for the Vortec heads, if I can find them then I would really consider it but I'm just gonna start with finding the 350 first.

Seeing how I'm on tight budget, I might just leave everything alone and go for goal of just getting it installed and started!

Given the budget and timing issue (Memorial Day), I think Vortec heads and intake should wait till the next engine.

Again, as another budget concious measure, find a block that has the maechaical fuel pump boss fully macined (you have to look inside to make sure. That will save you the expense of a marine electric fuel pump, wiring in an oil pressure switch, and probably a fuel pressure regulator, in additon to the need to fabricate new hard fuel lines.

 

[John_S]

Re: 5.0L Mercruiser Swap Question

Vortec heads would be a great power boost, but given your situation you may want to pass. An intake will add $2-300 to the budget.

Yea, thats why I was trying to make sure his existing wasn't freeze cracked. If he had to replace it anyways, no reason not to upgrade. Intakes for post '87 heads with canted center bolt for carbs are not that plentiful, either. Carbs were being phased out around the same time. You are 100% correct, that there will not be any factory carb intakes for votecs at the salvage yard. Marine take-off 2brls and aftermarket only.

 

[Saebin333]

Re: 5.0L Mercruiser Swap Question

Yea, thats why I was trying to make sure his existing wasn't freeze cracked. If he had to replace it anyways, no reason not to upgrade. Intakes for post '87 heads with canted center bolt for carbs are not that plentiful, either. Carbs were being phased out around the same time. You are 100% correct, that there will not be any factory carb intakes for votecs at the salvage yard. Marine take-off 2brls and aftermarket only.

Yeah, I'm definately gonna wait on the Vortec. Hopefully its JUST the block thats cracked but I'm soon to find out. I just hope I didn't make anything worse by running the engine with the ears connected to the outdrive. Like I said before, the engine sounded and acted as though there was no problems so no red flags came up until I checked the oil. I'm gonna do what I can and then just hope for the best. Thanks again guys for all your help!