350 mag wont start

[dan313]

I took the boat out this morning, While waiting to anchor I was idling and would bump it in and out of gear, I noticed a vibration (rumble) when I would take a little power. After being anchored for 5 hours I attempted to start the engine and it barely cranked. The batteries are not dead. After about 10 attempts I now have this high pitch wine, and the engine did not start.
I was towed back to the dock.

Any ideas??

 

[dwna1a]

High pitched whine? Check the starter bendix. It sounds as if the bendix is not engaging the flywheel.

 

[kevin27]

My bet is the engine had water in the cylinders and all that cranking broke the starter trying to compress the water. First ckeck the oil for milky look. If so pull the plugs. Being you said it ran rough(rumble) under power and turned over slow with good batterys you may be looking at an engine change or last least the heads and exhaust elbows/manifolds.

 

[dan313]

Good Morning,

I changed the manifolds two years ago with mercruser parts. I only put a 100 hrs on the boat since then. I'm going down to the boat this morning.
I'll let you know what I find.

Lenny

 

[dan313]

The motor is seized, Now I have to decide weather or not to go with the same motor 350 mag or a 383 stroker. What if anything has to be changed in order to install the bigger motor? I'm not too happy with the 350. The boat is under powered. But if the cost is too much than I will just replace with another 350 mpi

 

[Bob & Sue]

I know a couple people who have replaced their 350mags with the 383mag both are very happy with the difference in power & torque. If you go to a 383mag long block you should be able to use most of your existing parts, here are a couple good sites for compatability & ball park pricing I haven't used either one myself but one of the repowered friends used Doug Russell and was very happy with them.
If it were me I'd give them a call to discuss in detail any parts you might need either way you go.

Good Luck that really sucks.

http://www.dougrussell.com/engines-sterndrives/motors/mercruiser-mx-6-2l-mpi-bravo-package

http://www.perfprotech.com/lb-383-rm-05-up-865108r01/product/188643

 

[kevin27]

http://www.michiganmotorz.com/strok...njection-350hp-replacement-carbmpi-p-502.html

 

[dwna1a]

Lenny, I've been looking at these engines as well but the cost to replace both engines would be around $30g. My shop says they can sell my twins but still the cost scares the stuffing out of me. Can you please keep us informed as you continue down this path?

 

[dan313]

I've decided to go with a rebuilt Jasper Block. I plan on selling the boat in 3 years when I retire. I am going to replace the manifolds and risers. Even though I changed the manifolds in 2011 I am going to replace them. I figure better safe than sorry. I did have water intrusion on the port side. It happened when I pulled the throttle back in a tight turn. My mec thinks the water got in thru the exhaust manifold. The block looks like it has been under water for a long time. That's why the motor locked up. A new block was ordered this morning.
I'll keep you posted.

 

[dwna1a]

Thank you and good luck. The 87 34WE behind me cracked both heads after his thermostat housing failed, I feel for him