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Inboard Boat Motor Ignition Tune Up Guide

Inboard Boat Motor Ignition Tune Up Guide – Video Transcript

If you've noticed your boat hasn't been performing quite the way you're used to, this could be an indication that the engine needs a tune-up. What we're going to do today is kind of review an engine tune-up, of course we're going to keep in mind that there's a lot of different four-stroke type engines so that would mean there could be some different procedures.

We got four-stroke engines in the outboard world and we got stern drives and inboards that utilize four-stroke engines. These type of engines typically use point ignition or electronic ignition distributors, so what we're going to do today is really just talk about a point ignition tune-up and maybe some of the upgrades. Just a quick clarification, the difference in a point ignition versus an electronic ignition is under the rotor on a point distributor basically the points are a switching on/off device. For an electronic ignition distributor, instead of a mechanical point switching device we do it electronically and these would basically represent those components, a lot of different varieties.

So for now let's go over all the components we're going to replace. We're basically going to replace our spark plugs, we're going to replace plug wires, let's say that we've been five to six, maybe ten years before they've been replaced, we're going to replace our points, the distributor rotor, the condenser and the cap.

So let's start with the plugs. We're going to remove the plugs and we do want to pay attention to, what you might call, the burn pattern. One thing you want to pay attention to is if you have an excessive amount of buildup that could be due to burning oil if you will, so you want to take note to that, okay? But remember before you remove the plugs you do want to mark your plug wires and make sure that the firing order is back in the proper place. When replacing our plug wires, we do want to use marine grade wires, there is a bit of a difference. As you see here on our Sierra high-performance mag force wires, we use a brass terminal end okay? This is for corrosion prevention because we do know on electrics we do not like corrosion, if you use just a traditional automotive set we're inviting corrosion because of the high humidity we have in the marine industry.

From there let's say we replace our spark plug wires, then we're going to go into the distributor, remove the rotor and then we're going to replace the points. Before we do that let's take a quick look at the distributor shaft and make sure the bushings are real tight, because if it's loose we'll get erratic point bounce and we need to completely replace the distributor. So from there we're going to put a new condenser in, a new set of points, make sure you put a little cam lube on the cam lobes, this will help points from wearing out prematurely. From that point we're going to gap them according to the specifications, new rotor on and then we're going to replace the cap. A lot of times if a cap goes bad basically it could be from a lot of buildup on the terminals which could cause a short.

Again, on a marine distributor, we do want to make sure we have our gasket in place because we do have to contain the spark inside, that's a Coast Guard approval rating and also we have a spark arrestor on the side, automotive type distributors do not work in marine atmospheres. So now that we've done that you're probably going to need a few tools so that we can check dwell, which is for the point setting and then after that we're going to set the timing, again the spark plugs to dwell on the timing you want to follow the recommended specifications by the engine manufacturer.

Now let's say every spring we start our boat up and we notice it runs rough and you just tuned it up last year. That could be because we have oxidation across the points, so basically, or traditionally, point systems require maintenance year after year. Sierra International has a cure for that. What we have is an electronic conversion kit, what this does again just like the electronic distributors, we replace the mechanical points, on/off switch, with a magnetic on-off switch. This gives you years of trouble-free maintenance, your boat traditionally will start easier and we can get a little bit more performance out of this application, therefore we don't have to worry about that year after year.

Now remember when we talked about the distributor, if we had the shaft that was loose we could get erratic point gap, you would want to replace the distributor in that application. Now as we talked about the maintenance-free application, Sierra International also has an electronic replacement distributor, which is a direct bolt-on, it does come with the instructions, easy wiring, direct hookup and they'll give you pertinent information that's needed. So with that all said you should have trouble-free years of good boating with good engine performance that you were used to.