Marine Mechanics for Dummies?

[SamR]

6am at the ramp yesterday. Motor trims up then will not trim down. Both switches are useless. Batteries are only two seasons old and were showing 12+ volts. Three guys stand there looking like idiots as we come to the realization that we will not be going out to chase Tuna after all. I am determined not to let this happen to me again. It's time that I learn how to diagnose and service my motor. :x

For a complete novice who is reasonably competent in other mechanical areas, what is the best way to start learning? Books, classes, etc? I have yet to winterize or springize my boat. That's going to change too.

 

[Porkchunker]

First, I'd get a copy of the service (not operator) manual for your make/model of motor.

Second, I'd get a book coverign marine electrical. Chapman's has a chapter on marine electrical, and is a good start point, but doesn't have the depth necessary to diagnose and fix many things.

A good basic electricity book that covers AC and DC circuits and how to use a multi-meter to discover shorts, open circuits, excessive resistance at connectors, etc. would also be benificial.

BTW, it sounds like your problem is wiring. Did the battery have enough juice to crank the motor? If so, then there is a bad connector, broken wire, or fuse popped. If not, then first check the battery connections to make sure you are getting a good connection between the battery posts and the wires. A bad connection will keep the battery from getting a good charge, and will increase resistance to the point that large current draw motors (starting and tilt/trim) won't run. Clean the battery posts and all wires that attach to the battery, make sure the battery is charged and try again. If that doesn't solve the problem, then it is a wire/connector/fuse in the tilt/trim circuit...or possibly the tilt/trim motor itself. But before replacing a motor, absolutely rule out a battery or wiring problem.

Before replacing a battery:
1. Make sure it is topped off with distilled water (yes...even the so called "maintenance free" batteries are not truly maintenance free and need water from time to time)
2. Make sure all the connectors are clean and bright
3. Make sure it is charged and holds a charge
4. Make sure the alternator on the motor is actually charging the battery (no use killing a brand new battery to discover this)

Before replacing the tilt/trim motor:
1. Rule out a battery problem
2. Rule out a switch problem
3. Rule out a fuse/circuit breaker problem
4. Rule out broken wires, high resistance at connectors between the tilt/trim motor and the tilt/trim switches and between the tilt/trim switches and the battery.

 

[DaleH]

For a complete novice who is reasonably competent in other mechanical areas, what is the best way to start learning?

Ditto the OEM factory service manual, usually $50 - $60 and the BEST $$ you could spend. There is a wealth of "how to" and "trouble-shooting" info in those manuals, which are dedicated to your model and HP range, and not those of 20-years range of motors from 3hp to 250hp, like a cheaper Clymer or Seloc service manual attempts to cover.

Also, if the parts manual is a separate book, pick that up too, as the schematics show all the parts in their sequence of assembly and this helps immensely to guide you around the motor, IMHO.

Motor trims up then will not trim down.

You could have opened up the manual-bypass valve with a screwdriver, which would have allowed the motor to bleed down on its own.

Now, that said, did you hear the trim motor running when trying to trim down? I have seen a few instances where the tilt-tube gets gunked up to the point where it won't fall down on its own. Please advise if this was the error mode ... and I'll provide more detail on this problem and cure.

Both switches are useless.

If it was just electrical, you could have swapped out the UP from the DOWN relay and see if the problem followed the part. If so, most relays are Sierra relays that you can get at a good auto parts store for 1/2 the price of the SAME part from your dealer. Though I do say, I support my local dealer whenever possible.

Please let us know ... but yes, with a little knowledge, you could have salvaged that tuna trip ...

 

[SamR]

Thanks guys. Service manual will be on my X-Mas list. Here is a little more info. The motor trimmed up very slowly and then started to work at the normal speed after that. I trimmed up and down in the lot before my crew arrived. With the motor in the up position, I backed down the ramp and tried to trim down. No sound, no nothing. Thought that it might have been a power thing but I did not have the knowhow to confirm. Did a brief start with the motor up and out of the water. Worked but it was only on for a split sec.

 

[DaleH]

Sounds like the relay, if no trim motor sound when trimming down ...

To also diagnose, rap on the trim motor housing with a wood or plastic mallet while cycling the switch. If she moves better when rapped, then your motor needs to be re-built. If the housing is OK, then a good generator/starter shop should be able to rebuild her for $50-$60. Otherwise you'll need a new one.

OEM replacements built from ISO-certified shops can be had on eBay for ~ $110 or so.

 

[DaleH]

Note: Motor is OMC 1998 115hp fuel-injected DI ...

Sam, please look through the 2 sketches attached. These were downloaded from Johnson's website, which has links to all parts for all motors, see link here.

Look at sketch OB1: You should find the manual release valve on the trim motor by accessing the "big hole" in the port-side OB bracket that holds the powerleg and powerhead together onto the boat's transom. Release, turning counter-clockwise, slowly (watch body parts) using a LARGE regular bladed screwdriver. On older motors I have had to use a large impact tip, but you shouldn't have to.

Look at sketch OB2: You should be able to find the electronics module as pictured and simply swap the 2 trim relays.

... you could get out of this for < $25 and < 1-hour of your time ... email me if I can help you out more ...