Tach Stuck - WOT's Wrong

[imported_boatin clan]

We just bought a 1988 Sea Ray 19' bowrider with a Mercruiser 4.3LX engine and took it out on a local lake for the 1st time.

The boat ran great but I noticed 3 problems.

1. At WOT my tach was reading 3000-3400 RPM. My prop is a 4 blade with a 19 pitch. Too much prop maybe? I was expecting 1000 more RPM than I had.

2. When we were done for the day, I was getting the boat ready to trailer and I noticed that the tach was stuck at 1,000 with the engine off. Can you help me troubleshoot this? Loose wire maybe?

3. The trim guage is stuck on Trim Down" and does not move no matter where the outdrive is trimmed. ANy suggestions on troubleshooting this?

 

[Dunaruna]

Re: Tach Stuck - WOT's Wrong

[colour=blue]Problem #2 - does the tach go to zero when you turn the ignition on?

 

[imported_boatin clan]

Re: Tach Stuck - WOT's Wrong

[colour=blue]Problem #2 - does the tach go to zero when you turn the ignition on?

Do you mean before the engine turns over to start?

 

[Dunaruna]

Re: Tach Stuck - WOT's Wrong

[colour=blue]Yeah, just 'on', not 'start'.

 

[Don S]

Re: Tach Stuck - WOT's Wrong

Were you using the trim properly? If it's trimmed all the way down, the boat will plow and not get proper speed or rpm.
You also need to verify your tach is accurate. Merc and Volvo both recommend that WOT testing be done with an accurate shop tach. The helm instruments were never designed to be super accurate.
I have also seen many tachs that jump up to something other than zero when the switch is shut off, but returns to 0 when the switch is in run condition, without causing any problems with readings

 

[imported_boatin clan]

Re: Tach Stuck - WOT's Wrong

Were you using the trim properly? If it's trimmed all the way down, the boat will plow and not get proper speed or rpm.
You also need to verify your tach is accurate. Merc and Volvo both recommend that WOT testing be done with an accurate shop tach. The helm instruments were never designed to be super accurate.
I have also seen many tachs that jump up to something other than zero when the switch is shut off, but returns to 0 when the switch is in run condition, without causing any problems with readings

I'm not sure Don if I was doing everything right or not (gotta be honest) since I'm a newbie, but the boat seemed to take a while to plane. My thought was to trim down to force the bow down to allow me to plane out sooner. Once we did plane, the boat acted the way I described above. I will try to take the boat out next week and try to trim it up a bit and see if that improves the problem. Is the correct WOT RPM (assuming tach accuracy) 4,000 - 4,400 for this engine?

 

[imported_boatin clan]

Re: Tach Stuck - WOT's Wrong

I'm not sure Don if I was doing everything right or not (gotta be honest) since I'm a newbie, but the boat seemed to take a while to plane. My thought was to trim down to force the bow down to allow me to plane out sooner. Once we did plane, the boat acted the way I described above. I will try to take the boat out next week and try to trim it up a bit and see if that improves the problem. Is the correct WOT RPM (assuming tach accuracy) 4,000 - 4,400 for this engine?

 

[tystick]

Re: Tach Stuck - WOT's Wrong

I have a 4.3 merc 1990 and wot is approx 4800
so yes you seem to be 1000 less rpm then spec.

Does the trim guage stuck or switch? Does the tilt work at all?


you have the best signiture i have seen
I commend you as a new poster that you provide very complete info to others and should be noted1

 

[imported_boatin clan]

Re: Tach Stuck - WOT's Wrong

Thanks for the sig comment Tystick.

The trim guage stays pegged to the right at all times regardless of the outdrive position or tilt.

The drive does trim and tilt. My trim switches are for bow up/dn and trailer up.

I have read other posts out here that say if the trim senders are corroded, the lower unit has to be removed to get at them? Do I really want to have the lower unit pulled to replace them? Am I minimizing the importance of the guage?

Thank you all for bearing with my "newbie" questions.

 

[Don S]

Re: Tach Stuck - WOT's Wrong

That outdrive needs to be pulled at least once a year just for mainenance on the splines, gimbal bearing,and ujoints.
You would still have to remove the pivot housing and a lot of work to change the senders. You are the one that needs to decide if you want the gauge that bad or not.
Once you get used to the boat and how the trim works and what it does, you probably won't use the gauge that much anyway

 

[Fishstick1962]

Re: Tach Stuck - WOT's Wrong

Just a thought...If you are new to I/Os. Be aware that you also have a trim limit switch on your outdrive. (port side) If not properly adjusted you may over trim and cause damage. When full trim up (not trailering) the lenght of the trim cylinder from bolt to bolt(pin) should be 20 3/4 inches. (Learned the hard way) Also I have successfully changed my trim position sender without pulling the drive. My wires were good just the sender bad, so I opened the sender, removed wires and attached to new sender..no problem. Try adjusting the trim sender first though. Also, I see alot of tachs read 1000 when shut off, when key is moved bach to the "Run" position it should drop back down to "0". Happy Boating!

 

[Fishstick1962]

Re: Tach Stuck - WOT's Wrong

Just to clarify my previous post... never start the engine with the outdrive up in "Trailering position" as this will damage U-joints, yolks and gimble bearings. This means $$$$$. Adjusting the trim limit switch is a must! Again, I learned the hard way when I first got my I/O.

 

[imported_boatin clan]

Re: Tach Stuck - WOT's Wrong

Thanks for the advice Fishstick1962 and all. The tach did fall to 0 as soon as I put the key in and put the ignition switch in 1st position - sounds normal from the thread replies.

If I don't feel comfortable winterizing my engine / drive myself, what should I expect to pay a marine mechanic to do it for me? Any thoughts?

 

[MJ76]

Re: Tach Stuck - WOT's Wrong

You will likely pay $200 or more, depending on the shop rate, but make sure of what they do, because some people will pull the drain plugs and call that a winterization. A full service winterization should include fuel stabilizer, a test run, fogging of the engine, drain and antifreeze of the raw water cooling system, change of engine oil & oil and fuel filters. Also the drive should be pulled, gear lube changed, engine alignment checked, lubrication of the gimbal bearing, steering, pivot pins, and shaft / coupler, as well as an inspection of the bellows and a general looking-over. Also a good time to check trailer lights, brakes and bearings. When storing the boat, leave the drive down. It keeps the bellows in the relaxed position and keeps rainwater from collecting in the gearcase, where it could freeze.

Also, I don't know if your RPM issue was resolved, but don't overlook it - there is more than just poor performance at stake. The W.O.T. rpm range for that motor should be 4200-4600. If you are maxing out 1000 under that, you are asking for trouble. Continual lugging can and will do serious engine damage.

Check your trim limit. The limit for the old style Alpha 1 is 21 3/4 inches, center to center on the pins. As long as this setting is correct, you can ignore the trim gauge and just go by the feel and handling of the boat. If you can't get to 4400, I would (assuming no performance issues with the motor) definitely go down in pitch. You will probably see more speed as the motor turns on, you'll get on plane faster, and your motor will thank you.

 

[imported_boatin clan]

Re: Tach Stuck - WOT's Wrong

Check your trim limit. The limit for the old style Alpha 1 is 21 3/4 inches, center to center on the pins.

How do I check the trim limit? Is this with the drive in the full up position?

 

[MJ76]

Re: Tach Stuck - WOT's Wrong

You should have a trim switch (up/down) and a trailer switch. The trim limit is how far the drive will come up from the full down position using only the trim switch. So trim the drive all the way down, then trim it up using only the trim switch. If you hold the switch in the up position, at some point it should stop on its own. That is the trim limit. Take the measurement there.