B&D marine blower motor

[RiverDave]

shift interrupt switches spotted:

I'm thinking not so much.. Lol

 

[BDMar]

yup they're right there. good enough for a schiada!

Not a shift interrupt switch. It is there to let the PCM know when the engine is in gear to help maintain idle quality. As a matter of fact, a shift interrupt switch would be a hindrance for a Bravo shifting. They require the gear stack to be spinning smoothly to shift properly. There is a Bronze tolerance ring that is eccentric on the bottom of the fwd and rev gear. As it spins it helps force the shift fork to move the cone clutch. Mercury has never installed an interrupt switch on a Bravo application.

A little more info about the interrupt switch for your Alpha. Working properly, they only activate when shifting OUT of gear into neutral. The taper on the "dog clutches" on the gears makes it very difficult to come out of gear without the switch. When they activate going into gear, either the adjustment is off or the intermediate shift cable needs replacing.

 

[ka0tyk]

Not a shift interrupt switch. It is there to let the PCM know when the engine is in gear to help maintain idle quality. As a matter of fact, a shift interrupt switch would be a hindrance for a Bravo shifting. They require the gear stack to be spinning smoothly to shift properly. There is a Bronze tolerance ring that is eccentric on the bottom of the fwd and rev gear. As it spins it helps force the shift fork to move the cone clutch. Mercury has never installed an interrupt switch on a Bravo application.

A little more info about the interrupt switch for your Alpha. Working properly, they only activate when shifting OUT of gear into neutral. The taper on the "dog clutches" on the gears makes it very difficult to come out of gear without the switch. When they activate going into gear, either the adjustment is off or the intermediate shift cable needs replacing.

thanks for taking the time to explain it. i love learning stuff like this.

 

[Outdrive1]

Not a shift interrupt switch. It is there to let the PCM know when the engine is in gear to help maintain idle quality. As a matter of fact, a shift interrupt switch would be a hindrance for a Bravo shifting. They require the gear stack to be spinning smoothly to shift properly. There is a Bronze tolerance ring that is eccentric on the bottom of the fwd and rev gear. As it spins it helps force the shift fork to move the cone clutch. Mercury has never installed an interrupt switch on a Bravo application.

A little more info about the interrupt switch for your Alpha. Working properly, they only activate when shifting OUT of gear into neutral. The taper on the "dog clutches" on the gears makes it very difficult to come out of gear without the switch. When they activate going into gear, either the adjustment is off or the intermediate shift cable needs replacing.

X2. Usually the cable is the cause of any problems with the interrupt switch. Super common on those setups.

 

[OCMerrill]

thanks for taking the time to explain it. i love learning stuff like this.

You're spot on to look for it since you became educated in the world of Alpha when building your boat but it's only Alpha.

Alpha's need it because shifting the lower into gear with even idle load is tough on them. I had mine removed for years but put it back on a couple years ago after I blew an Alpha up and wanted the new one handled like the factory intended. Bravo all happens in the upper, Alpha all in the lower.

You can nearly kill the engine if you don't shift it with some speed but that momentary break in engine load allows the dogs to do their thing. Also I have experienced too high an idle and the dogs just skip and make a horrible sound.

 

[SMPLV]

Exactly. I thought I said that only in a broader explanation. lol Keith got it.

This engine would need to idle at a minimum of 1300 to be happy with a "Dave idle". AGAIN... when shifted, the engine gets leaner. It needs a richer mixture when in gear. Richer idle mixture (not lean Dave) makes for surge. 1300 idle VERY unfriendly around docks, non-transmission drives, etc.

Dave, not poking jabs at you, but you don't understand why this engine surges. You would have to know a whole lot more about the internals of this, or any engine to say it should idle differently.

Last example: This engine will idle at 1000 (barely) with no surge. Shift it and it will die. Not maybe, it will die. A Bravo Sterndrive will weld the cone clutch to fwd gear if you chose to shift it at 1000+. (read my first response) Now set the idle at 1300 (the minimum it will be happy at a "smooth" idle) shift it, then bring me the drive.

I really did try to explain in earlier posts why it idles that way. I'll tell you what, I'll do the video Hammy suggested to show the effects of idle mixture. Then I'll fix it so it works in a boat. lol

What about shifting to drive from a 900-1000 rpm idle with an SCX4 drive?

 

[Tommy Gun Images]

What about shifting to drive from a 900-1000 rpm idle with an SCX4 drive?

I’m sure was the same answer 10 years ago

 

[SMPLV]

I’m sure was the same answer 10 years ago

Well duh haha, but I didn't see any talk about an SCX4 and we all know there's no comparison to a Bravo drive haha

 

[jetboatperformance]

I love my surge once when I was off work for a while my son tuned my blown Jet tuned most of the surge out of it with boost referencing and tuning , I hated it this latest build is not boost referenced. Probably gonna leave it that way.

 

[rivrrts429]

What about shifting to drive from a 900-1000 rpm idle with an SCX4 drive?

Not really a big deal but like a crash box in a v-drive you shift at the low end of the surge. Most surge can be tuned out of it but higher HP stuff it’s more difficult with a roots style blower.

 

[SMPLV]

Not really a big deal but like a crash box in a v-drive you shift at the low end of the surge. Most surge can be tuned out of it but higher HP stuff it’s more difficult with a roots style blower.

My engine doesn't seem to like anything under 850-900. And IMCO states a maximum of 800 rpm shifting. I don't have blower surge. Just trying to find the sweet spot to where my engine doesn't die when I shift into gear and not destroy my drive.

 

[DarkHorseRacing]

What about shifting to drive from a 900-1000 rpm idle with an SCX4 drive?

I assume you’re talking about a cone clutch SCX4.

I have a cone clutch SCX with a TCM blower motor and it idles right around 800-1000. I hate shifting the drive with the idle that high but TCM set it up that way. Supposedly the motor interrupter does its thing, but it’s still a good solid thunk when it shifts.

I’ve considered adding IMCOs stand-off box that contains a transmission and getting rid of the cone clutch in the upper.

 

[lbhsbz]

Old school = no surge.. Surge came around with political correctness and all that goes with it.

What kind of boat do you have?

 

[RiverDave]

What kind of boat do you have?

Ah the jokes.. if I wasn’t in a meeting right now for the wife I’d be test driving an e ticket. lol.

 

[rivermobster]

This thread is a Serious time warp.

RIP.

 

[SMPLV]

I assume you’re talking about a cone clutch SCX4.

I have a cone clutch SCX with a TCM blower motor and it idles right around 800-1000. I hate shifting the drive with the idle that high but TCM set it up that way. Supposedly the motor interrupter does its thing, but it’s still a good solid thunk when it shifts.

I’ve considered adding IMCOs stand-off box that contains a transmission and getting rid of the cone clutch in the upper.

Correct. I cringe when I shift into drive haha. Have you asked TCM about it? Especially since they set it up that way. What is the motor interrupt you're referring to? Is this in the tune?

 

[DarkHorseRacing]

Correct. I cringe when I shift into drive haha. Have you asked TCM about it? Especially since they set it up that way. What is the motor interrupt you're referring to? Is this in the tune?

Whatever this thing is has to do with the shifting.

Not in the tune as far as I know.

This motor/drive combination drives me batshit crazy. Motor stalls constantly after shifting into forward gear while idling. Does it frequently and consistently at altitude, does it rarely out in Havasu but does do it. BCM can’t fix it, TCM can’t fix it, and I’ve pestered Whipple to no avail. Whipple and TCM thought maybe the idle wasn’t set right, TCM thinks the fuel pressure is too high or too low, Whipple also thought the ignition module in the distributor needed to be changed (it was changed three years ago) or the IAC (changed last year). BCM just says the boat runs perfect for them in Havasu.

Like I mentioned previously, the cone clutch has to go. A digital shifting trans would solve this whole thing. Need the stand-off box to fit it without moving the engine.

 

[ToMorrow44]

I assume you’re talking about a cone clutch SCX4.

I have a cone clutch SCX with a TCM blower motor and it idles right around 800-1000. I hate shifting the drive with the idle that high but TCM set it up that way. Supposedly the motor interrupter does its thing, but it’s still a good solid thunk when it shifts.

I’ve considered adding IMCOs stand-off box that contains a transmission and getting rid of the cone clutch in the upper.

FWIW my TCM 825 idled right at 800 and shifted in/out of gear like butter with no clunk (TCM XR drive). No stall or stumble, didn’t even change rpm when in gear vs neutral. Definitely sounds like something not quite right with yours.

 

[DarkHorseRacing]

FWIW my TCM 825 idled right at 800 and shifted in/out of gear like butter with no clunk (TCM XR drive). No stall or stumble, didn’t even change rpm when in gear vs neutral. Definitely sounds like something not quite right with yours.

Yeah I’m going to mess with the throttle plate and see if I can close it a little. The IAC if it works properly should allow the idle to be ok. I’m waiting to do that at altitude where I have the most trouble with the idle.

 

[Racey]

What about shifting to drive from a 900-1000 rpm idle with an SCX4 drive?

usually they like shifting under 900

My engine doesn't seem to like anything under 850-900. And IMCO states a maximum of 800 rpm shifting. I don't have blower surge. Just trying to find the sweet spot to where my engine doesn't die when I shift into gear and not destroy my drive.

Is it carbed and distributor?

 

[SMPLV]

Yeah I’m going to mess with the throttle plate and see if I can close it a little. The IAC if it works properly should allow the idle to be ok. I’m waiting to do that at altitude where I have the most trouble with the idle.

I’m wondering if your blade needs to be cracked open more…
Like maybe your IAC is working too hard. That was my first issue and got a lot better after I gave it more blade. The rest for me I believe is in the tune.

 

[SMPLV]

usually they like shifting under 900

Is it carbed and distributor?

Whipple 8.3. You built the surge tank for it Shane haha.

 

[DarkHorseRacing]

I’m wondering if your blade needs to be cracked open more…
Like maybe your IAC is working too hard. That was my first issue and got a lot better after I gave it more blade. The rest for me I believe is in the tune.

I tried that on a TCM recommendation, it just made the idle come up above 1000. However, the IAC being replaced last year I can give that another try.

 

[HST4ME]

I have a bin with $20,000 of broke imco parts, motors are 632's with 14/71's and won't idle under 900. I've fattened up the idles to lope more but they bang hard with max5 35's, and it will continue to eat parts. The SCX is still a bravo, with all the bravo shortcomings. Just the numbers are moved up the scale. Not a fan of them at all.

 

[bonesfab]

I tried that on a TCM recommendation, it just made the idle come up above 1000. However, the IAC being replaced last year I can give that another try.

The throttle plate should be adjusted so the IAC is barely open at idle in neutral. That gives the Iac more room to recover when it goes from load to no load. Idle speed is programmed in the ecu. The ecu will do what it has to with the iac and timing to maintain the commanded idle speed.

 

[DarkHorseRacing]

The throttle plate should be adjusted so the IAC is barely open at idle in neutral. That gives the Iac more room to recover when it goes from load to no load. Idle speed is programmed in the ecu. The ecu will do what it has to with the iac and timing to maintain the commanded idle speed.

For the IAC, does that mean the plunger is almost all the way in, or almost all the way out?

 

[82daytona]

FWIW my TCM 825 idled right at 800 and shifted in/out of gear like butter with no clunk (TCM XR drive). No stall or stumble, didn’t even change rpm when in gear vs neutral. Definitely sounds like something not quite right with yours.

Same here

 

[SoCalZero]

Is turbo surge accepted the same way as blower surge? Asking for a friend.

 

[Racey]

Whipple 8.3. You built the surge tank for it Shane haha.

What ECU? I never saw the boat in person

 

[BingerFang]

Ah the jokes.. if I wasn’t in a meeting right now for the wife I’d be test driving an e ticket. lol.

And if my sister had a dick she would be my brother…

 

[shintoooo]

And if my sister had a dick she would be my brother…

Not in 2024

 

[bonesfab]

For the IAC, does that mean the plunger is almost all the way in, or almost all the way out?

should be all the way in. as in closed. Should be barely a whistle out of it. You can put your thumb over the hole and if it sucks it hard, the iac is too far open.

 

[4Waters]

I love my surge once when I was off work for a while my son tuned my blown Jet tuned most of the surge out of it with boost referencing and tuning , I hated it this latest build is not boost referenced. Probably gonna leave it that way.

Did you ground him?

 

[SMPLV]

What ECU? I never saw the boat in person

Motec M130.

 

[Racey]

Motec M130.

There is some trickery that can be done by dropping the idle timing very low and leaving the initial throttle position open more, but it can be a fine line to walk when you are spraying all the fuel in front of the blower and you have no ability to get equal fueling per cylinder.

Timing is a far quicker response to a stall than an IAC is, as it can change and have an immediate effect on the very next firing event, not having to wait for the mechanical delay of the air and fuel mass to make it's way all the way down to the cylinder.

 

[SMPLV]

There is some trickery that can be done by dropping the idle timing very low and leaving the initial throttle position open more, but it can be a fine line to walk when you are spraying all the fuel in front of the blower and you have no ability to get equal fueling per cylinder.

Timing is a far quicker response to a stall than an IAC is, as it can change and have an immediate effect on the very next firing event, not having to wait for the mechanical delay of the air and fuel mass to make it's way all the way down to the cylinder.

What you’re describing…is this retarding the timing? I was talking to Steve (Captain Hook DCB) as he has almost the same setup and he said they were having the same issue and retarding the timing at shifting helped the problem.
I’m currently seeing if I can get Dave on the boat to go over the tune and set it straight. The boat moves when I’m on the throttle! Just sucks right now shifting haha.

 

[bonesfab]

Less timing lower idle. More timing higher idle. In the cars I sometimes throw some timing at the dip to help catch the stall when you put it in gear or come to a stop.

 

[lbhsbz]

Ah the jokes.. if I wasn’t in a meeting right now for the wife I’d be test driving an e ticket. lol

When did E-ticket start making old man pontoons with cripple walker access?

 

[bonesfab]

When did E-ticket start making old man pontoons with cripple walker access?

Next thing you know there will be handicap slips in the marina.

 

[lbhsbz]

Next thing you know there will be handicap slips in the marina.

Don't use the word "slip" around RD....that's what happened last time....handicap people slip a lot in the marina....gotta be careful though so they don't break their ankles.

"not skid # 24"...doesn't have the same ring to it, but sure sounds safer.

 

[28Eliminator]

When did E-ticket start making old man pontoons with cripple walker access?

RD approves

 

[BingerFang]

RD approves
View attachment 1367058

Was that the guy that was in the capitol? Thought I saw a photo of him in there.

 

[Tank]

I don’t care what anyone says. I LOVE blower surge, always have!

Our boat actually doesn’t have much. But this was a cold start and surged pretty good.

 

[BingerFang]

When did E-ticket start making old man pontoons with cripple walker access?

 

[Fun Times]

Whatever this thing is has to do with the shifting.

BDM touched on it in post number 52 in his first sentence... Your photo is called an "in gear indicator switch" that lets the PCM know if it's in gear or not.

B&D marine blower motor

shift interrupt switches spotted: I'm thinking not so much.. Lol

www.riverdavesplace.com

Item number 18,

Shift Bracket, Bravo

Shift Bracket, Bravo

www.mercruiserparts.com