Replacing 1978 351 c.i. V-8 OMC Stern Drive in 1978 Starcraft 21' ...recommends (?)

[Klondikeking]

Hi,
I picked up a late-70s fiberglas-hull Starcraft American outfitted with a 240 HP V-8 OMC engine model #990251J and stern drive model #981918. Paid about $3400 US for the boat/trailer with a full custom canvas and a bunch of fishing gear.

A couple of people I have talked with have recommended replacing the engine and leg with something more modern (Quicksilver/Mercruiser) (?) due to the advanced age of the motor and lack of availability of parts, etc., for the OMC.

Any recommends on what brand-configuration of motor set-up to go with if we decide to go ahead with a new engine/leg set-up?

Will I be able to find something that fits the existing hole in the transom without a lot of framing/fiberglas work?

Excluding labour, what kind of investment (roughy) for parts/materials am I looking at to do that kind of swap-out? Am I better to pay more for a new fuel-injected plant, or should I look at a re-build that is perhaps carbureted?

Is it worth converting to digital gauges at the same time as a retrofit?

This is a sweet boat and I couldn't afford something this size new, so just thinking about the future...

Any advice/warnings/your experiences much appreciated.

Thanks in advance,
Rod J.
Whitehorse, Canada

 

[Lou C]

1) The OMC stringer system, does not match up with anything else ever built
2) the way it is designed, you may wind up having to reinforce the transom since the stringer drives supported all the weight of the engine/drive system on the engine stringers. Later OMC drives (Cobra) Merc and Volvo all used the transom itself for the support of the rear engine mounts and transom mount for the outdrive. As such the transom must be stronger than it would for an OMC stringer boat.
3) engine wise your best bet is a carburated GM 5.7 Vortec, EFI on an old boat is a complete waste of money, and can cause a host of potential expensive headaches. That and a Mercruiser Alpha 1 Gen 2 outdrive system money wise and parts availability wise is your best bet.
4) evaluate the condition of the rest of the boat before embarking on this major project.
5) seeing as how you are going to wind up rebuilding the transom and can't use any of the OMC stuff you have, sell that off if it's in decent shape. Instead of going I/O, you might have a pod for an outboard fitted and go with modern 4 stroke outboards power. The best, but most expensive upgrade.

 

[Scott Danforth]

First, welcome aboard

Second, to swap to any other motor/drive combination you will need to rebuild your transom and stringers. You will NOT find something that fits your current hole

Your current OMC motor and drive is completely different than anything else

Assume $1500 USD for materials to rebuild your transom, stringers, support. More if you have to buy tools, etc. A whole lot more if you have to ship resin and gel

For the motor and drive, get a complete boat with a rotten hull. It will be cheaper than trying to piece things together

Expect to pay between $1000 and $3000 USD for a 20 year old boat with a good longtail. More if you want to waste money on EFI

Up to you if you want to waste money on digital gauges

If you came here before you bought the boat, you would have gotten the advice to skip anything OMC or anything Ford. However you own it now.

I would simply run the boat as-is and do repairs as-needed. Then spend the money on the boat you want

 

[Klondikeking]

First, welcome aboard

Second, to swap to any other motor/drive combination you will need to rebuild your transom and stringers. You will NOT find something that fits your current hole

Your current OMC motor and drive is completely different than anything else

Assume $1500 USD for materials to rebuild your transom, stringers, support. More if you have to buy tools, etc. A whole lot more if you have to ship resin and gel

For the motor and drive, get a complete boat with a rotten hull. It will be cheaper than trying to piece things together

Expect to pay between $1000 and $3000 USD for a 20 year old boat with a good longtail. More if you want to waste money on EFI

Up to you if you want to waste money on digital gauges

If you came here before you bought the boat, you would have gotten the advice to skip anything OMC or anything Ford. However you own it now.

I would simply run the boat as-is and do repairs as-needed. Then spend the money on the boat you want

Thanks for the quick reply, Scott.

I have tools and skills and friends in terms of carpentry/resin work. I am not great with carbs, as my vehicles are EFI...but I get your point on the price of EFI versus carbureted. Do you think carbs are superior on a marine application?

My plan is to run the boat with the existing plant...just trying to map out what my options might be if/when it becomes necessary to replace the stock config...

Thanks again,
RJ

 

[Klondikeking]

1) The OMC stringer system, does not match up with anything else ever built
2) the way it is designed, you may wind up having to reinforce the transom since the stringer drives supported all the weight of the engine/drive system on the engine stringers. Later OMC drives (Cobra) Merc and Volvo all used the transom itself for the support of the rear engine mounts and transom mount for the outdrive. As such the transom must be stronger than it would for an OMC stringer boat.
3) engine wise your best bet is a carburated GM 5.7 Vortec, EFI on an old boat is a complete waste of money, and can cause a host of potential expensive headaches. That and a Mercruiser Alpha 1 Gen 2 outdrive system money wise and parts availability wise is your best bet.
4) evaluate the condition of the rest of the boat before embarking on this major project.
5) seeing as how you are going to wind up rebuilding the transom and can't use any of the OMC stuff you have, sell that off if it's in decent shape. Instead of going I/O, you might have a pod for an outboard fitted and go with modern 4 stroke outboards power. The best, but most expensive upgrade.

Hi Lou, thanks for getting back so promptly.

I am definitely guilty of not doing as much research on this boat as I should have before pulling the pin.
She had two owners before me. The first owner parked her for many years and the second owner used periodically. It has not run regularly for over five years. She has been under cover since new, so in surprisingly good condition in terms of hull and fittings. Not mint, but pretty close. As far as mechanically...still figuring that out.

I am intrigued by the possibility of a "pod mount" for outboard power. Would that be suspended on the lower end of the transom? Are there sketches/examples of this kind of this install out there?

Thanks,
RJ

 

[Scott Danforth]

Do you think carbs are superior on a marine application?

Carbs and EFI have their place. However in a boat carb would be my preference over EFI

First, EFI does not get you any more power or economy

However mainly because in 15 years after the boat is built the EFI bits are NLA and the carb bits are still available from 2000 different sources

Not to mention, I can field strip a carburetor in 20 minutes and put it back together in another half hour while on the water if needed and injectors must be sent out for cleaning

 

[Lou C]

Agree 100%
I like a well tuned Quadrajet; after a cold start they run very well. Even better is a pre Vortec engine that can use a simple trouble free mechanical fuel pump. For a few reasons electric pumps can be a headache in boats….