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Newbie's questions after maiden voyage

M

Michael Alapaki

New member
Lost my cherry today on a 1986 Regal Sebring bowrider with MerCruiser 4.3L Alpha sterndrive. Engine purred well, but I have two newbie questions:

1) While cruising at 3000 RPM, I think I could get more speed from the 205 HP motor if I changed the engine trim up or down. Can someone tell me what to do with the engine trim? (The trim gauge and speed-o-meter don't work.) Should I cruise with engine fully lowered or at half-trim, or what?

2) After a freshwater cruise, what should I do? Do I need to run hose water through the engine?
 
From what you said, I understand that your tilt-trim actually works, but the dash indicator does not respond. Correct? If so it is very likely that removing and cleaning your tilt-trim sensors will likely remedy this. Buried deep in this site are several posts describing how to clean and adjust these sensors. I do not have my fast computer up now or I would locate references, but a couple of searches should find them. Not hard, I have done it on a couple of boats and the most recent was on a boat similar to yours.

The purpose of the tilt-trim is to level out the boat hull in the water for more efficient performance. In these smaller boats, weight distribution of fuel, passengers/crew, and miscellaneous loads seriously affect boat responses and you definitely want to get this function operating correctly.

With heavy loading or pulling up a skier, you would likely trim down for better pull, and trim up as speed increases to have less drag. Do not trim up to the point the boat starts to porpoise.

When the speedometer fails to respond, many times the pitot tube on the stern is plugged up, the rubber tube from the pitot tube to the speedometer on the dash is leaking, split, or plugged with mud. Inspect the tubing and the small hole in the leading edge of the pitot tube. A small wire can be used to open plugged hole or tubing. Or replace the tubing if it is aged/bad. So far in my life I have never had to replace the dash speedometer unit. All failures to date have been in the pickup are, either the tubing or the small entry hole being plugged. Muskrats will also chew thru this tubing.

With a little patience, I believe you will be able to fix your problems with next to zero $$ investment.
 
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Wow. Thanks, David. That's exactly the education I needed. I'll get right on it.
Kim I appreciate your input. I learned a lot from the specs you provided. Thanks.
 
Michael, definitely not to take away from what David and Kim have suggested.
Those are all good points, but I'll add this since you are new.

You OEM spec'd WOT RPM is a test RPM ONLY, as to determine if the propeller pitch and diameter, as well as the drive ratio are correct for the engine.
It is NOT an RPM to be sustained for any duration.
The goal is to see if the engine will reach the OEM specified WOT RPM and with the boat loaded as you would normally.

Examples:
If you cannot reach WOT, you are likely over-propped.
If you can exceed WOT, you are likely under-propped.
Error on the side of being under-propped.

NOTE: engine must be in full tune to perform a WOT RPM test.


Two most effective speeds will be "hull speed" and "planing speed". Your planing speed is best when you reach planing attitude and just a tad bit more.
This gets the hull more so on top of the water reducing friction some.
3,000 rpm may not quite do this..... depends on the boat and the boat's load, prop design, etc.

Trimming the drive "out" does add efficiency. You'll find a sweet spot.

If you are running in lake/river water, you can still flush, but it may not be as necessary as if running in brackish or salt water.


.
 
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see last paragraph How the trim/tilt works

Before you tear anything apart or replace wiring and switches, test it out; firstby visual inspection by pulling back and forth on the wires while operating theswitches and then test with a meter. At the commander switches ,the red wirewill always have 12 volts. The green wire gets 12 volts when the trim toggle isheld down. The blue wire gets 12 volts only when the toggle is held up or thetrailer switch is pushed in. The purple wire is part of the limit switchcircuit.

If the switch voltages are as they are supposed to be then go to the trim/tiltpump assy. and make sure the purple wire connector (single wire) and the bluewire connector with two blue wires on one side of the connection are notcorroded or loose. These are the trim position and limit switch wires. Pullthem apart and inspect; they should be clean and tight; reconnect them. Ifnecessary, trace the wires to the front of the engine near the slave solenoid.One wire is grounded near there and the other is connected to a terminal. Ifyou don't get a voltage reading at the terminal junction, apply 12 VDC to seeif the trim gauge moves. If it does, check for voltage back at the trim pumpconnections. If there is no voltage there, apply 12 VDC there to check gaugemovement.

Next check the three wire connector (RED, BLUE & GREEN) at the pump assy.This plug can vibrate loose and cause your problem. Pull it off and see if the pinsare clean and not corroded; reconnect it.

The RED wire in the plug sends 12 volts from the pump assy. to the toggleup/down and trailer up switches. The BLUE & GREEN wires bring 12 volts fromthe toggle trim/tilt and trailer switches to the two solenoids on the pumpassy.

The GREEN wire goes to the DOWN solenoid while the BLUE wire goes to the UPsolenoid.

Did you check the switches with an ohmmeter? The trim/tilt switch is a 2-wayswitch and will show continuity only when it is toggled in each directionbetween two of the wires.

Up toggle connects the RED wire to the BLUE wire. Down toggle connects the REDwire to the GREEN wire. The TRAILER UP switch also connects the RED wire to theBLUE wire.

The OD trim limit switch will only send voltage to the trim/tilt switch in theupward toggle position if the OD limit switch is below the adjusted trim limitthat keeps the OD being out of the water.

To test the limit switch circuit, lower the OD to the down position and slowlyraise it with the trim toggle up until it stops. Then measure the distancebetween the trim cylinder attaching bolts. If the distance is approx. 20 +/-1/4inches, then the trim limit switch is adjusted properly and the commander trimtoggle switch is working in the up/down mode.

Go to the trim/tilt pump assy. and make sure the purple wire connector (single wire)and the blue wire connector two blue wires on one side of the connection arenot corroded or loose. Pull them apart; they should be clean and tight;reconnect them. Next check the three (RED, BLUE & GREEN) wire connector atthe pump assy.The RED wire in the plug sends 12 volts from the pump assy. tothe toggle up/down and trailer up switches. This plug can vibrate loose andcause your problem. Pull it off and see if the pins are clean and not corroded;reconnect it.

The BLUE & GREEN wires bring 12 volts from the switches to the twosolenoids on the pump assy. The GREEN wire goes to the DOWN solenoid while theBLUE wire goes to the UP solenoid.

Disconnect the trim/tilt assy. wires from the battery and then check each ofthe nuts and studs on the solenoids for clean and tight fittings. Each solenoidhas three wires and the buss bar connected to it. The bases of them have ablack ground wire and a small blue wire to one and a small green wire to theother.

On top of each solenoid, the large BLUE wire from the pump motor attaches to alarge copper stud with the solenoid that has the small blue wire at the base whilethe large GREEN wire from the pump motor attaches to a large copper stud withthe solenoid that has the small green wire at the base.

The other copper solenoid studs are connected together with a copper buss bar.One of the two studs will also have a funny looking 110 amp fuse attached tothe bar. The large RED wire from the battery connects to the 110 amp fuse. Thislarge red wire is the power for this buss bar. A small RED wire attached to thebar stud sends 12 volts to the switches which in turn sends the 12 volts to thesolenoids which turns on the pump motor.

Important: if the studs on the either solenoid are dark and not like a cleanpenny, especially the BLUE wired solenoid, this solenoid is failing due to ageand/or a loose bottom copper stud nut. The dark color comes from heat generatedinside of the solenoid by the contactor because it is arcing like weldingsimilar to points wearing out. Change the solenoid.

Cleaning Trim Limit Switch & Trim Position Sender

For the trim/tilt, if the wires from the limit switch (port side) and trimposition sender (starboard side) are in good condition, they (Switch or sender)can be disassembled to clean out the old hardened grease. SCRIBE the sides ofeach one and the OD for a reference mark before removal. Clean out the oldgrease and pump fresh Mercruiser 2-4-C grease thru the zerk fittings beforereinstallation. Clean the small brass contact points with solvent and a pencileraser until shiny; repack w/ 2-4-C grease and reinstall by aligning reference marks.
 
Should I cruise with engine fully lowered or at half-trim, or what?
Click to expand...
All the way down to start. When it reaches plane start raising the OD a few clicks on the trim switch...you will hear the engine RPM slowly increase as it reaches optimum trim. You will also hear the RPM change quickly when you have gone up to far.
 
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