Sea Ray Sundancer 250DA Motor/Boat Build Project, Splashed.

[devildogae]

Bought a 1995 Sea Ray Sundancer 250DA with known engine failure. Journey with me on the road to gettting this mistreated beauty queen back on the stage, or lake in her case. It was a brine boat, but I don't think she will see much brine in her future. She has a majorly cracked Mercruiser 5.7L block and cracked head. Found lots of milkshake as I was pulling her dress off. I havent started disassembly of the short block yet, had to get a 3/4 ton truck to move her around and now I'm looking for a big tree to lift the short block out. I did source a GM 5.7 350 from the same year as a donor motor for parts such as the block and bare heads. I'm not sure what parts I will be able to salvage from the Merc, such as the crank and connecting rods. Either way she will be getting rebuild and put to use. The donor block is in the machine shop now.

 

[devildogae]

[No message]

 

[Scott Danforth]

if the heads need machining, I would seriously consider vortec heads
if the crank needs machining, I would jump up to a stroker crank (same dollars) big boat like that needs the grunt of a 383

 

[devildogae]

if the heads need machining, I would seriously consider vortec heads
if the crank needs machining, I would jump up to a stroker crank (same dollars) big boat like that needs the grunt of a 383

What would be the difference between the marine crank and a stroker? That's an auto crank right?

 

[Scott Danforth]

No. Your stock motor is the same cast crank as any truck. There is no such thing as a marine crank. Only cast vs forged and 1 piece RMS vs 2 piece RMS

The stock crank stroke is 3.48" A stroker crank has a stroke of 3.75 or 3.875 depending on which one you buy

 

[devildogae]

No. Your stock motor is the same cast crank as any truck. There is no such thing as a marine crank. Only cast vs forged and 1 piece RMS vs 2 piece RMS

The stock crank stroke is 3.48" A stroker crank has a stroke of 3.75 or 3.875 depending on which one you buy

That's good to know. I'm sure there is more to it than just slapping in a stroker crank, if I was going down that road, what else must be adjusted from stock?

 

[Scott Danforth]

depends on what you want to do. building motors is easy. determine what you want to do up front......machine the block....buy parts....assemble motor.

if you want to build a stroker, determine that prior to buying pistons, etc. most rotating assemblies can be purchased as a complete kit.

you can even start with a new block for about the cost of buying a used block and machining it.

 

[kenny nunez]

Keep in mind that if you go the stroker route that the flywheel & harmonic balancer will have to match the crankshaft.
Your boat definitely needs more torque. For a boat like that the more the better.

 

[devildogae]

Keep in mind that if you go the stroker route that the flywheel & harmonic balancer will have to match the crankshaft.
Your boat definitely needs more torque. For a boat like that the more the better.

I'd love to do a stroker, and that might have been an option if I can planned on that earlier. I'm to far along now to make those changes. That is something that I will think about for the next build on this. I just want to get her in the water at this point. Building a stroker is something I would want to take my time with, because I'm pretty new to building engines. I've built 1 zx6r engine and 1 Mercruiser 120.

 

[devildogae]

Finally got the short block out of the boat. I tried to take a picture of the tow truck pulling the boat motor out, but I was bright out and I didn't take it as I thought I did, bummer! It was very easy with the tow truck. I finally got the motor dissasembled and I found the culprit for the seized motor. It was a bent and twisted rod from hydrolocking.

Even though I didn't own the boat at the time, that's still a lesson for me, inspect the exhaust manifolds and replace. The major failure was in cylinder #6. The crank is in fantastic shape.

I'm still waiting on my donor block from the machine shop, apparently he was injured and was closed all last week, not sure if it will be open this coming week. Time is a fleeting!!!!

 

[devildogae]

Got the donor block back from the machine shop just in time because the only guy that works in that shop, and only local shop got hurt the next day and has been out for over a month now. I had to drive an hour to get the new pistons put on the rocker arms. I decided to do the head job on both heads myself. Wire wheel to clean up all surfaces, lapped the valves in by hand and power washer to clean it all up. I have both heads installed and I bought pedistal mount roller rockers. I'm hoping that will get me close to, but under the 300hp range. Will post more pics.

 

[devildogae]

Making quick progress. The engine is built and back in the boat. I started her up in my garage and broke the cam and lifters in. Replaced a bad trim pump and got a wrecker to come out and help with installation. Those guys are amazing, only charged me $85 for the install. A local marina wanted $250 just to lift it out after I had disconnected everything prior!! Gotta take a break for it for a week for family vacation, then back at it.

 

[devildogae]

[No message]

 

[devildogae]

Newly rebuilt motor is back in the boat and I started her up for the first time in the boat. I can't get base timing set because my line is scattering all over the place. I did retard the timing from where I had it and it's running very well and about 650 rpm's. I am getting a bit of fuel vapors out of the carb, so I think I might have a fuel pressure issue or a float pin or float out of adjustment. I'm kicking myself for not rebuilding the carb when I had it off the engine. A few videos!

 

[devildogae]

[No message]

 

[Rick Stephens]

Great to hear! I would use a shop tach to set RPMs. The ones on a good timing light work decently. Better accuracy than your dash gauges anyway.Get the timing perfect before you consider it ready for water.

 

[devildogae]

Great to hear! I would use a shop tach to set RPMs. The ones on a good timing light work decently. Better accuracy than your dash gauges anyway.Get the timing perfect before you consider it ready for water.

Thanks for the reply. I used a timing light to get the engine to idle about 650 rpm's. But when I hit the strobe button, my line is all over the place. I'm going to go back and make sure I don't have any crossed wires. If that fails, I will start by replaceing the wires and cap. I'll check all the wires and see if I continue to get erratic reading.

 

[devildogae]

Can I get a moderator to edit the title as splashed!!

Took our maiden voyage yesterday. Was great fun. Big boat, easy to come off the rollers. Had more difficulty getting it back on the trailer straight... My wife made a montage video, I will try and get but here is what I have.

 

[NHGuy]

I think you have Thunderbolt V ignition. If so, the timing scatter will go away when you shunt the distributor. Warm up your engine, ground the purple and white wire, set your timing, idle, and mixture.
Then shut it down, remove the ground wire and you will be set.
The reason you don't get a steady timing light without the shunt is because the TB V constantly corrects timing.

 

[devildogae]

I think you have Thunderbolt V ignition. If so, the timing scatter will go away when you shunt the distributor. Warm up your engine, ground the purple and white wire, set your timing, idle, and mixture.
Then shut it down, remove the ground wire and you will be set.
The reason you don't get a steady timing light without the shunt is because the TB V constantly corrects timing.

Thanks for your help. I think I have the Thunderbolt IV ignition. That's what's on my engine cover, and I havn't been able to locate any purple/white wire. I have tried. I think I'm going to try with a different timing light soon.