5.7 Mercruiser Replacement Question

[mlsande21]

The engine in my Glastron GS249 which I have owned for about 2 months, is bad. Apparantly the original owner let the block freeze and had it replaced. They used a 350 automobile block instead of a marine block. After about 200 hours, it is just coming apart.....just my luck!

Anyway, my mechanic is going to pull the engine and send it to his rebuilder who will replace all the parts that need replaced, including the block.

However, I found another place that specializes in repowers and they will get a longblock from Mercruiser with all new parts and put my intake and exhaust manifolds on it for about the same price......$5,000. Which you you experts perfer if you were me?

Thanks.......Mike

 

[Fishermark]

Re: 5.7 Mercruiser Replacement Question

That seems mighty steep for reusing your manifolds. If memory serves me correctly I paid less than that for a complete 2003 5.7 liter turn-key Mercruiser crate engine. granted, that was a couple of years ago, but I would do some additional searching if it were me. Just my humble two cents. :/

 

[Bondo]

Re: 5.7 Mercruiser Replacement Question

"They used a 350 automobile block instead of a marine block. After about 200 hours, it is just coming apart....."

It's the Exact Same Block,........ So Please Explain.........

 

[Buttanic]

Re: 5.7 Mercruiser Replacement Question

$2500+shipping gets you a new heavy duty Vortec engine. You may have to get a different intake manifold, flywheel and coupler but you would still come in well under $5000.

http://store.summitracing.com/egnsearch.asp?N=400129+320096+115&autoview=sku

 

[mlsande21]

Re: 5.7 Mercruiser Replacement Question

"They used a 350 automobile block instead of a marine block. After about 200 hours, it is just coming apart....."

It's the Exact Same Block,........ So Please Explain.........

My mechanic tells me that if you use the internal parts from the marine engine and put them in an automobile block the tolerances are different. It will run fine for a while, but evenually will quit. I don't know......I can only go with what I am told.

Whatever happened, I do need a new engine now. Do you think it's that big of deal to have someone replace the parts that need replacing as opposed to having a new long block with all new parts installed?

I appreciate the info, that's what these forums are for and they are great!!!!

Thanks.....Mike

 

[Reel Poor]

Re: 5.7 Mercruiser Replacement Question

Look at this Complete Drop-in Mercruiser Remaned 5.7 Liter

 

[Limited-Time]

Re: 5.7 Mercruiser Replacement Question

"They used a 350 automobile block instead of a marine block. After about 200 hours, it is just coming apart....."

It's the Exact Same Block,........ So Please Explain.........

My mechanic tells me that if you use the internal parts from the marine engine and put them in an automobile block the tolerances are different. It will run fine for a while, but evenually will quit. I don't know......I can only go with what I am told.

Whatever happened, I do need a new engine now. Do you think it's that big of deal to have someone replace the parts that need replacing as opposed to having a new long block with all new parts installed?

I appreciate the info, that's what these forums are for and they are great!!!!

Thanks.....Mike

Seems your mechanic is looking to sell you a 5 grand repower. I repowered (5.7 short block) with a Jasper reman for under 3K. As bondo said there is no difference. The machining tolerances are the same for both engines.

 

[calwldlif]

Re: 5.7 Mercruiser Replacement Question

My mechanic tells me that if you use the internal parts from the marine engine and put them in an automobile block

:0
Darn auto blocks

 

[MJ76]

Re: 5.7 Mercruiser Replacement Question

All other things being equal, I would go with the Merc motor, hands down. Take your average 350 car engine, stick it in a boat and run it all day at 4800 rpm and see how well it performs and how long it stays together. I've seen too many "racecar" motors put into boats that just never ran right. There is no difference in the block, or the machining tolerances that I'm aware of, but the power demands are different, requiring a certain cam profile, and there are other components that are used to prevent corrosion and to allow the engine to handle the extra abuse that a marine engine has to endure. I'm not saying that it's not possible to build an adequate marine motor, but for the same price (or even a little more), go for the Mercruiser motor, prop it correctly, and you won't regret it.

 

[f_inscreenname]

Re: 5.7 Mercruiser Replacement Question

I hate that crap! Marine block???? Ask them where they get a marine block from. Maybe they dip them in saltwater before they ship them from the same Chevy plant. :|
Like said before its only the cam profile that is different. If you bought a motor for a truck I bet the cam would even be right.

 

[Buttanic]

Re: 5.7 Mercruiser Replacement Question

The Mercury 350 cam profile is the same as that for a 1 ton Chevy truck.

 

[lilmandavis]

Re: 5.7 Mercruiser Replacement Question

just paint it and put a merc sticker on it!! punch out the steel freeze plugs and put in the marine ones and 'POOF' your truck motor becomes a marine engine. lol

 

[Flukinicehole]

Re: 5.7 Mercruiser Replacement Question

I went through this when I repowered my boat about 5yrs ago.I put in a warmed over 305 w/roller rockers a little head work and brass core plugs.I have a closed cooling system and have never had a problem with it at all.In fact I got a new hull and dropped this engine in for the season with plans on building a bigger engine over the winter.Truth is this one runs so good I`m going to leave it alone.The boat only tops out at 34 but I dont need to go any faster.This was a factory chevy crate engine with a towing/rv cam that a friend ordered when he worked at chevy.If I were you I would find a new mechanic it sounds like this one is trying to take you for a ride,or he just doesnt know.Good Luck with it .

 

[tommays]

Re: 5.7 Mercruiser Replacement Question

The real isssue is that the GM crate motors do not have any coverage for a marine install

Gm wants you to go through a marine OEM even if its the same

Tommays

 

[mkast]

Re: 5.7 Mercruiser Replacement Question

I think alot of these guys that repowered for XXX dollars did the work themselves. I get the feeling you are paying "your mechanic" to swing the wrenches.
Depending on how tall your cash pile is...your mechanic is going to get alot of the pile one way or the other.
I'd go with the marine longblock, if you are not doing the work yourself.

 

[MelLandry]

Re: 5.7 Mercruiser Replacement Question

My Chevy crate truck 350 longblock with new exhaust manifolds and elbows came to around 3300 installed and included servicing the outdrive while everything was off. ($1800 in parts, 20 hours labor).

 

[MelLandry]

Re: 5.7 Mercruiser Replacement Question

I went through this when I repowered my boat about 5yrs ago.I put in a warmed over 305 w/roller rockers a little head work and brass core plugs.I have a closed cooling system and have never had a problem with it at all.In fact I got a new hull and dropped this engine in for the season with plans on building a bigger engine over the winter.Truth is this one runs so good I`m going to leave it alone.The boat only tops out at 34 but I dont need to go any faster.This was a factory chevy crate engine with a towing/rv cam that a friend ordered when he worked at chevy.If I were you I would find a new mechanic it sounds like this one is trying to take you for a ride,or he just doesnt know.Good Luck with it .

Out of curiosity, where did you get your power curves to determine what the correct WOT should be on your new engine? Or did you just use the old WOT?

 

[Flukinicehole]

Re: 5.7 Mercruiser Replacement Question

The RV/Towing cam in this engine makes power from 1200 to 4200 rpm.It drops off after 3800 but not to much.I dont have the cam card anymore wish I could help out more but these are the #`s I remember.It is a little slower out of the hole (new boat weighs 4500 dry)but not lugging.All cams have a card with them to tell you the proper operating RPM.

 

[cj11l]

Re: 5.7 Mercruiser Replacement Question

Just a quick note on the machining questions. It is recommended to give an extra .001 on the piston to wall clearance due to the block not getting as warm and expanding as much. That being said, we have used standard clearance before and not had any issues.

Never could understand how Marine engines were so much more $ than auto/truck engines. All in the advertising I guess!8)

Chris Laarman
Ottawa Engine and Performance

 

[hudman]

Re: 5.7 Mercruiser Replacement Question

After breaking down on the mississippi river, I didnt want to take any chances, I bought a NEW COMPLETE 383(bored and stroked 350) from mercruiser, mpi, with everything , for 6250 delivered. the only thing i needed to replace it was a fuel inlet fitting. it was complete with exhaust , even y pipe, with a 2 yr unlimited warranty. it is a exact direct replacement for your engine. im glad i did this instead of trying to fix the old motor.... good luck