Don, Rodbolt...Who Ever?

[Trent]

OK, we all know about the shift interrupt switch on the Alpha drive Mercruisers. Got a boat in last week, a Cat boat with twin diesels driving Alpha Gen II units. Now I've never seen diesels driving Alpha's before, usually Bravo's. My question is, there is no shift interrupt switch. How is it breaking the torque on the lower unit to unshift the drive? Owner said it shifts just fine. These are little Mercruiser 4 cylinder diesels and was told they were Cummins. Mounted forward with jack shafts back to the drive.

 

[Don S]

Re: Don, Rodbolt...Who Ever?

Good question, unfortunatly, I can't answer your question but now you have peeked my interest. Is this the 1.7L diesel?

 

[TilliamWe]

Re: Don, Rodbolt...Who Ever?

Was there a transmission of any kind at the end of that jackshaft? Just a guess

 

[rodbolt]

Re: Don, Rodbolt...Who Ever?

cause at an idle a diesel is so rough it does not hold a steady impulse on the propshaft. thats why the volvo diesel drives (DP-E) have the nedox cones. it helps keep the slippage at idle speeds from wearing the cone and gear wheels. that coupled with most diesels idle a bit slower than most gas motors and therefore dont load the propshaft as hard at low speeds. its all about unloading the propshaft long enough for the clutch to withdraw from the gear.

 

[Don S]

Re: Don, Rodbolt...Who Ever?

Good point rodbolt, hadn't even considered that. I sure know the Volvo DP-E and even earlier drives rattle the upper a lot. Even the Bravo drives rattle a lot with diesels.

 

[Trent]

Re: Don, Rodbolt...Who Ever?

Very good point indeed Rodbolt. Thanks again guys.

 

[waterone1@aol.com]

Re: Don, Rodbolt...Who Ever?

Never ran into this myself, was scratching my head. Thanks rodbolt...that makes perfect sense.

 

[rodbolt]

Re: Don, Rodbolt...Who Ever?

ever hear a jack shafted diesel carolina classic or Albermarle? at an idle in netural you would swear the shafts were going to exit the hull. some gas motors do it, most notably the 8.2 gas engine. its do to the lack of a solid idle. but it can also be the first sign of an engine miss .<br /> but I gotta see how long a set of genII's will hold up behind a diesel, unless they are tiny ones.

 

[Don S]

Re: Don, Rodbolt...Who Ever?

As far as I know, and I may be way off base, the 1.7 is the only one using the Gen II drive.

 

[Don S]

Re: Don, Rodbolt...Who Ever?

ever hear a jack shafted diesel carolina classic or Albermarle? at an idle in netural you would swear the shafts were going to exit the hull.

Haven't ever seen one of those boats up here, but as far as the noise goes, yes I've heard it. And on an aluminum boat with no sound insullation, makes you just put your hands up in the air, and with your eyes wide open you back away slowly. Then find someone to shut the thing off.

 

[rodbolt]

Re: Don, Rodbolt...Who Ever?

I could not imagine it in an AL hull. its quite a racket in a glass hull. <br /> I have not seen the 1.7L genII combo yet. but any 4 banger diesel is going to have some wild power pulses at idle

 

[bigbrownbuku]

Re: Don, Rodbolt...Who Ever?

novurania inflatables are making it an option in some of their equators. sea trialed a few and all the extra weight and the nice big teak scoop on the swim grid = pull up slowly or sink.