Need help on 1997 370 motor replacement

T

TommyZ

New Member
Aug 20, 2011
21
San Diego, Ca
Boat Info
1997 370 Sea Ray Sundancer
Engines
454 7.4
Hi , my name is Tom and i am was just lucky enough to purcahse a 1997 370 sundancer that needs new engines. The former owner started to dismantle the old ones so really not even a good core between the two.

The trannys seem ok. These were Generation 6 454 7.4 carb motors. My question is this:
What do I put in
I can buy two 454 long blocks and source accessories ( I'm good at finding stuff)
I can buy complete engines ( hard to find this way and a bit pricey)
I can really step up and look to replace with high output and give the boat more Horses and hopefully run it less hard to acheive the same speed
I can replace with Mercruiser official replacement for the 454's which are the 6.2 liter wither carbed or MFI.

I plan on keeping this boat for a long time and like to fish and cruise. Mileage is a concern and I would like to make the right decision for the long haul

Your input is very much appreciated

Tom
 
I'd buy brand new 454s if you can find them. I'd go with the lower HP version which will probably last longer than the HO version. The 6.2 does not have enough cubic inches for a boat your size. Just my view of things. There are new 454s listed on the internet that have the marine enhancements added by GM and which are reportedly the same engines that Merc, Volvo, and Pleasure Marine buy and then modify with their own risers, ignitions, etc.
 
Oh yea, and one more thing.

Anything I should be doing while the engines are out of the boat? Hopefully I won't have to do this for the next 10 years. I was reading about the generator,water heater or vacuum system.

I am very new to this size boat as my other is a 1993 270 DA, very different.

Thanks again

Tom
 
Generator is difficult to get at, but with engines out of the way - very easy. Spark plugs for the genny are on the outboard side so check the genny out carefully. Now is the time to service it thoroughly. The vacu flush is on the opposite side of the boat, but much easier to access IMHO, so shouldn't be an issue. Water heater is under the mid cabin cushions and so is not dependent on the engines being out of the way tall.

As far as engines go, I would go MPI if at all available. Better starting and fuel economy overall and I think the engines might have a bit more pull. Stay with the same size as you have and don't worry about the H.O., it doesn't make that much of a difference.

Consider getting the muffler arrangement changed out to the water lift mufflers on the newer boats. It may make the engines last longer since water ingestion was a problem on earlier 370's. Look at most of the 1998 models are set up that way.

And check out www.370sundancr.com for lots of resource pictures and info.

Gene
 
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Russ Calasant said:
Tom,

Please follow up and post your findings, I am interested in what you find out and decide to do.

Thanks
Click to expand...

Russ are you going to have replace your motors too? What was your prognosis?

I just missed out on seeing Tommy's boat firsthand because I couldn't get away from my trial here in San Diego. It would have been an interesting fact-finding mission.

Gene
 
RubberDuckeeToo2 said:
Russ are you going to have replace your motors too? What was your prognosis?

I just missed out on seeing Tommy's boat firsthand because I couldn't get away from my trial here in San Diego. It would have been an interesting fact-finding mission.

Gene
Click to expand...

Gene,

It's not good- it's been very slow going. I will post on my thread. I hope all is well with you.
 
Don't know if you want to go this far, but another board member repowered with Yanmar diesels, and then drove it from Ft. lauderdale to Grenada on its own keel! I believe it's in the USVI now. I have some great pics of the repower, and you might be able to find them here.
I've driven this boat with the factory 3116 cats, and that was a real pleasure. If I was really going somewhere all the time, I'd definately consider a diesel repower. But, you'd really need to keep it a long time to make that worthwhile/
 
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Saint Max has 2007 6.2's. only 950 lbs per side. Great engines....VLPITA to access for impeller replacement.

If I was going to the expense you are about to go to, I would contact http://boatstoreonline.com/OFFSHORE420.html.

They build a 420 HP stroked 5.7 engine that weighs about 50 percent less, runs on 87 octane fuel, has a 5 year warranty, transmits NEMA 2K info v. Smartcraft and is so simple even a caveman could work on them. He has my number and as soon as he finds someone who wants 6.2's I am in.
 
Put in 2 new short blocks they are about 5000 each rebults can take 2 or 3 engines before get good one.
 
Go with Yanmars, if you plan on keeping her a long time.. Gas is too expensive in CA... you will have to replace you props and genny, but in the end it will be worth the extra cost...
 
While making the decision, besides considering your needs and how you'll use your boat, it's important to consider what makes more sense for the others when the time comes to sell her. Be carefull with your choise of smaller blocks. Even though they may work fine for you and make perfect sense financially people always will go by the rumors of underpowered boat (even when it's not true). It's not common to see 340/360 with small blocks, so I can see how a 370 with small blocks will be moved to the bottom of the buyer list.

As for diesels, even though I agree with Rod's point regarding gas prices, I don't think that the price difference between new gas engine vs. Diesel ones will justify it. I don't know if your current genny is in working order, but it's a 3rd engine that will have to be changed if you go with diesels.

Lastly, I would suggest to hear Dale's (MasterFab) opinion and review details of how he rebuilt his 340, it's trully ammazing, I've seen it myself.
 
If you are considering diesels, then consider factory re-manned Caterpillar or Cummins engines. Your boat handles very well with either the 3116 Cat or the 6BTA Cummins and either engines will get your cruise GPH down to 16-18 gph.

The downside is that the conversion is very expensive. The actual cost of the engines is pretty low, but the cost for everything else that must be changed is usually a deal breaker.............transmissions, shafts, shaft seals, props, engine beds, generator, instrumentation/senders, fuel returns, fuel valves and manifold, fuel filters, and labor.
 
There is a fellow on anther boating site that has a set of 502's for sale. He bought them for an engineless Sonic project boat that jumped off the trailer in transport. Now he has a set of boatless engines!

PM me for the info.
 
Alex, thank you for the kind words - hopefully it won't go to my head!

Clearly, this is a decision that needs careful consideration, in regards to resale value, how long you intend to keep the boat, how much you use it each year, what you want out of it, and several other factors. I considered a diesel repower on my 340, but the engine room in the 340 is smaller than your 370, the hull is a bit shorter and narrower, and I did not want to create a weight imbalance with heavier diesels. As Frank said, the cost can run away quickly as well, with all the ancillary items that have to be changed too. In the end, the added range and economy of the diesels is extremely attractive, but it will be take a lot of years to recoup the added costs, so you have to carefully consider if you'll own the boat that long. A better option might be to repower with gas engines, sell the boat, and buy a diesel boat, if that's really what you're after. Only you can make these decisions.

Now, if you decide on a gas engine repower, there are things that can be done to improve economy and performance, but these are incremental improvements, and will still never get the boat to sip fuel like a diesel. You can't beat the physics and chemistry, after all.

It would help to know what exactly you have in your posession at the present time. Do you have the complete 7.4L engines and accessories that were originally in the boat? (Things like front engine dress items, brackets, pulleys, oil pans, front engine covers, valve covers, intake manifolds, etc.) If you have all these items, a pair of 7.4L longblocks is about the most economical way to repower, and the boat will be in essentially original condition when you finish. Just be sure to replace any wear items like exhaust manifolds, risers, exhaust hoses, etc. On a side note, I think your boat was rigged with the log style exhaust, so I would definitely convert to the water lift mufflers during the refit. Be sure to mount the mufflers as low in the vessel as possible, and be very careful that the down angle on your exhaust hoses meets Mercruiser specifications, at a minimum. A steeper down angle is even better. There are a host of other items to consider, but that can wait until you make your decision on which way you're going to go.

Having said all that, I'm going to go out on a limb now, and recommend what I think I would do, in your situation, especially if you don't have all or most of the 7.4L engine accessories. As many already know, GM discontinued the manufacture of 8.1 engines at the end of 2009, so new 8.1s are no longer available. Mecruiser now offers new 8.2L inboards, but they are only available with DTS, so you'd have to convert your boat to install them, and that is another expensive proposition. Personally, I prefer the reliability and ease of maintenance with the conventional controls, so I did not pursue this option. The 8.2s are also relatively new, with an unproven tack record, and I did not want to be a test bed for Mercruiser's latest and greatest.

However, Mercruiser recently began offering what are called 8.1+ engines. These are 8.1L engines that are rebuilt, by Mercruiser, and incorporate all the newest external dress items - Gen III fuel cooler, dry joint exhaust, the latest EFI, single point water drain, etc. These are what I chose for my 340. They come with a full 3 year warranty, are fully assembled, and will plug right in to your existing engine harness (with an adapter - they use the newer 14 pin style connector). They will give you a slight power increase, increased torque at low RPM, and will allow for increased cruising speeds at lower RPM, when propped accordingly. And, your existing motor mounts and transmissions are fully compatible. Combined with a modern 4 bladed prop, your economy will be improved as well. There is also a subjective benefit, in that a combination of water lift mufflers and reduced cruise RPM results in a substantially quieter boat - and that's a great way to help sell the whole thing to your wife!

Only you can decide, but we are here for you to help answer any questions as they arise. Oh, by the way, welcome to CSR!

Dale
 
THESE have been hanging around ebay for a real long time. Would certainly fit nicely and would move the boat with the greatest of ease. There is the problem of all the ancillary costs, as Frank said. I think you have 1 1/2" shafts - not sure you'd need to beef those up, but if you do, figure about $2k for that. Then you start the hunt for a new generator.

I consider a diesel repower sort of a fairy tale thing - kinda like "what would I do if I won the lottery." You are starting with a clean slate so you have so many options open to you. You will never recoup the additional expenditure in fuel savings - there have been many case studies on this topic. A very intelligent friend of mine did the math when he bought a showroom new Carver 396 - he said he'd have to put 100 hours on the boat over a 10 year period to break even.

That being said (and of course, debatable), you would create a "one of a kind" 370 that will be more valuable and much easier to move at sale time. I'm sure you got into this boat for a song, but most everyone has budget constraints. Sometimes, what you have to think about is "how much would it cost to replace this boat with a diesel powered equivalent?" My old girl may cost around $75K to repower with diesel - where can I get a diesel powered 36' sedan bridge for the money I'd sell her for + an additional $75K? They're out there, but they're just as old as mine and at least I know what I've got.

Enough of that - I didn't see in any of Tommy's posts that he was interested in diesel. We have big plans or you Tom!

As for small blocks, I think that would be a mistake. You have a big, beamy and heavy (14500lb) boat there and I've heard Masterfab era 340s called "underpowered" with 6.2s. I think it would create a stigma. You may have the HP but not the torque. If you have parts from the old 7.4s, I'd search for new long blocks and piece things together. A new heat exchanger is probably $600 but you can make your old ones like new for about $150 each at a local radiator shop.

With the engines OUT, I'd be SURE to do a FULL bilge rehabilitation. Clean/scrub and repaint while it's all open. Skeetobite, who did some sort of major repower project on his 370DB. Fantastic presentation on his amazing project. You'd have to find it here on CSR. I'll go look and post a link if I locate it.

GOOD LUCK and be sure to keep us posted.
 
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I also need to repower my 310 HP, 7.4 MPIs on my 99' 370(a long sad story).

Has anyone had any dealings U.S. Marine Engines out of Kent WA, or know anyone who has, and can give me a recommendation. They claim to provide an exceptional reman beefed up 454 long block with higher HP (375, 410, 425, etc) and torque and economy with a 7 yr/500 hr warranty. They have some BBB claims against them in the last 12 months but claim most of those are from installation and/or setting the timing issues. Sounds like the engines I want but don't want to trade one problem for another.

Also, any advice on going with a “new” long block (pretty much stock @ 310 HP w/ 500 ft-lb torque @ 3800 RPM vs. a similar reman long block where the price difference is around $3K more for the new long block.
 
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