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Discussion Starter · #1 ·
Hey guys…I have an issue with my trim switch that I thought I’d ask about. This is an Alpha one mercruiser outdrive. I’ve checked the fluid level on the hydronic pump first. it was a bit low when it started acting up and I filled it with no change.
This outdrive lowers just fine using the trim switch on the throttle arm, but does not respond to the up direction. But…. If I use the trailer mode button, it raises fine.
So there is nothing wrong with the hydraulic portion of my system. How would I go about testing the two direction switch? This is an older throttle / shift control set up, so parts are not available. Any suggestions or help with this would be appreciated…. Kirk
 

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Either (with power off) check continuity between the leads while switching between up/off/down, or pull the switch and (with power on) jumper the leads to see if the desired action happens as if the switch were being depressed, or (with power on) check voltage at the leads while switching between up/off/down.
 

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It's the trim puck (sender ) on your outdrive. The fact you can trim up with the trailer button pretty much confirms this, that switch by passes the trim sensor. If you don't want to change it out right now, you can take the cover off and clean the contacts. Don't disassemble it, just clean with fine emery cloth and contact cleaner. Put back together with dielectric grease,,,gregg

the trim sender should be on the port side, the other one on the starboard is the limit switch
 

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If you want to R/R it, do both, the leads from each go thru a common hole in your transom shield, it's a pain in the arse that's why I post to try and clean it first. But if its too far gone and corroded you'll have to go all new,,,gregg
 

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Discussion Starter · #7 ·
Thanks for that BB…. I was thinking that the trailer mode had to bypass the trim switch somehow. It Makes sense now…. I thought one of the pucks was a relay to the trim gage? That one is missing completely on my outdrive. While I do a lot of my own repairs, I still have a boat mechanic that does the bigger projects I’m not comfortable with, or have the tools to do it. I asked him about it and He told me that installing a new one was a pain in the arse too, so I’ve lived without it and trim by feel……But trimming your prop angle after coming up on plane is something I don’t want to do without. I hate plowing water with the bow.
I’ll do some tinkering with the switch and see what happens. Kirk
 

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One is the trim and it is tied to the indicator on the dash, and the trim switch on you controls, the other is the limit switch, once it is set to the correct adjustment, it stops you from over trimming while on plane. the trailer button over rides that limit for trailering. Many of us with I/O's trim with the tach, and never really use the gauge. I haven't replaced my pucks and they need it, it's a winter project in my mind. I use my tach and see the difference in real time with my Floscan meter, GPH usage drops down a little and the GPS cruise speed mph inches up. I don't run my boat hard so I'm not worried about over trimming, I just know the sweet spot for my engine now,,,gregg
 

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Discussion Starter · #9 ·
I never really associated rpms with trim adjustment. I typically drop it down all the way for decent hole shot, then bump the trim button to bring the bow back up once she’s on plane.

I put a 4 blade lower pitch prop on this boat last year and it slips up on plane at 2500-3000 rpms real easy without punching it to WOT. I’m running a 4.3 mercruiser that has plenty of power, but I don’t run it hard. Cruising speed is real nice at 3800 -4000 rpms and about 30 mph. it tops out about 4600-4700 with this prop. But I rarely run it very long at WOT, but it’s good to open her up now and then for short jaunts. What I really like is the responsiveness at lower rpms. It’s excellent in rough water, and turns on a dime with this screw. Kirk
 
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