6 replies to this topic

[CaribeSurf]

Hello to everybody. I just purchased, my first boat ever, a 1997 Speedster, with twin Rotax 720. The boat is not in great shape but I got a good deal on it. I assumed I would have to do some mechanical fixes to get it running where it should be but I got to a point where I'm over my head. I live in Puerto Rico and we have a lot of ocean to run on.

I tried testing the Speedster in the water (ocean) before I bought. However, the engines started but they would not rev-up. The previous owner was moving to mainland and didn't have time to get it checked out. Hence the good deal. I later found out that the neutral switch was the problem and replaced it. Out of water, both engines started and rev-up nicely (in foward mode).

I dropped it in the beach, both engines started ok, and the boat ran like crazy for about 10 minutes, when the right engine quit. I was able to get it started but it sounded like it was running on one cylinder. Changed spark plugs but didn't improve any.

I pulled it out of the water and a friend check for current at the spark plug. He advised me to replace the spark plug cable on one cylinder. I did. I also put new spark plugs again. I started it and after cleaning up a bit it rev-up good. I dropped the boat on the water, again, and within a couple of minutes it began doing the same thing. I tried starting it again but I guess it was flooded and it didn't start.

The left engine is running fine, but I noticed the exhaust manifold had a small hole in what I guess is a water seal. The water was being sprayed actually over the front spark plug of the same engine and it did not seemed to be hitting the right engine, which was giving me problems. I sealed the hole with epoxy but did not try anything else since I had to wait for it to hardened. There are no obstructions in the impeller housing.

Does anybody have any suggestions on what could be causing this? By the way; I checked compression on both engines and the right is the best with 145 psi.

[rickster]

I do not think the neutral switch would have something to do with performance. It merely sends a message to the system not to turn on if the gear is not in neutral. I had a 1996 sportster and once in the water had to disassemble it, bypass it, and then obviously replace it.

I would think the problem is electrical. Check the electrical box. Maybe a faulty rectifier (I don't know if your boat would use one or two). Maybe the ignition coil for that engine. Maybe a losse fuse on that box (not the accessory fuse box, but rather a box located inside the engine compartment, on the backside of the seats (I think), that you need to remove srews in order to get to the insides).

Also, maybe a faulty ground wire on the engine - these are located (I think) below the engine?

I would lean towards a loose engine ground, as the problem seems to happen while on movement.

Finally, I would suggest the following:

Remove both sparks and see if the have the same condition. If the spark form the cilinder that gave you problems is cleaner, you may have a blown gasket, allowing too much water in to the chamber. Anyways, Put the electric spark cabs on the mount, remove sparks, spray quick lube into the cilinders, and crank the ignition so that the cilinders get lubed. Put more lube, and put back the sparks. Next spray lube onto the carbs through the little hole. Turn on the engine, connect the hose, start the water,and shut off the gas valve. While it burns the left fule on the lines, keep spraying the carbs. As soon as you feel the engine going slightly up and down as it runs out of gas, stop lubbing the carbs, turn the water off and then the engine off. I used to do this before and after use, and my rotax 720 never had a problem.

VERY IMPORTANT - NEVER RUN WATER THORUGH THE FLUSH CIRCUIT WITHOUT THE ENGINE ON. This will flood the engine creating a backup and damages. On other engines, as in Mercs, you first start the water, then the engine. On this rotax you start the engine, then water, stop engine, then water.

I'm no mechaninc, but hope this will help you out.

[tiggerman]

Hello to everybody. I just purchased, my first boat ever, a 1997 Speedster, with twin Rotax 720. The boat is not in great shape but I got a good deal on it. I assumed I would have to do some mechanical fixes to get it running where it should be but I got to a point where I'm over my head. I live in Puerto Rico and we have a lot of ocean to run on.

I tried testing the Speedster in the water (ocean) before I bought. However, the engines started but they would not rev-up. The previous owner was moving to mainland and didn't have time to get it checked out. Hence the good deal. I later found out that the neutral switch was the problem and replaced it. Out of water, both engines started and rev-up nicely (in foward mode).

I dropped it in the beach, both engines started ok, and the boat ran like crazy for about 10 minutes, when the right engine quit. I was able to get it started but it sounded like it was running on one cylinder. Changed spark plugs but didn't improve any.

I pulled it out of the water and a friend check for current at the spark plug. He advised me to replace the spark plug cable on one cylinder. I did. I also put new spark plugs again. I started it and after cleaning up a bit it rev-up good.  I dropped the boat on the water, again, and within a couple of minutes it began doing the same thing. I tried starting it again but I guess it was flooded and it didn't start.

The left engine is running fine, but I noticed the exhaust manifold had a small hole in what I guess is a water seal. The water was being sprayed actually over the front spark plug of the same engine and it did not seemed to be hitting the right engine, which was giving me problems. I sealed the hole with epoxy but did not try anything else since I had to wait for it to hardened. There are no obstructions in the impeller housing.

Does anybody have any suggestions on what could be causing this? By the way; I checked compression on both engines and the right is the best with 145 psi.

If both cylinders are firing, more than likely fuel/carb related. Check your filters (at front of engine compartment). Given the age, chances are the carbs are in need of an overhaul as well. Next time out, when/if it runs poorly, pull out the choke lever for the right engine while accelerating and see if it makes a difference in the performance of that engine. If it improves, get the carbs overhauled or get kits and doo it yourself. There are small filters in the carb itself as well and they doo get clogged. These engines idle high when out of water because there is no load on the impeller. If they run well out of water and run poorly in water, it's been my experience that it is fuel related.

[CaribeSurf]

Thank you for your responses.

This is what I have done so far. I took the boat to an experienced mechanic and he, after inspection, recommended overhauling both carburators. He also changed a 3/4 moon disk he said act like valves and a couple of exhaust gaskets. He tested the boat on a calm river and both engines worked fine according to him.

It was my turn to try. I drop it at the beach, the same engine began running the same way as before (like on one spark plug), would not go pass 4K rpm's. Both engines idle great. About 10 minutes later it started to sharply increase and decrease in rpm's until all of a sudden it went to 7k rpm's and stayed there for a hell of a joy ride.

After a couple of hours and a few mandatory rests; your body takes a beating on the ocean waves, I went for the longest ride of the day, everything ok. At one point I noticed my fuel gage and I was right below quarter tank, so I decided to turn around based on the 1/3 rule. Once I was very close to the place I was anchoring the boat I decided to do a very sharp 180 deg right turn, and bingo the right engine (same engine) began doing the same, 4k rpm's max.

I have a couple of theories; one is that the ignition coil for that engine is what is called tired and when under stress fires only one plug. The second theory is that the gasoline is dirty. I replaced the filters attached to the panel. The old ones, specially the filter for the right engine, where very dirty. Didn't try the engine after replacing fuel filters.

Any comments.

[tiggerman]

Did the "mechanic" do the overhaul or is that still lacking? If not, there are still a couple tiny fuel filters in your carbs that may be clogged or clogging- I still think fuel problem.
The disk he replaced was the rotary valve, which is the intake valve for the engine.

[CaribeSurf]

Well, is me again. The mechanic I took the boat to did install a new kit on both carburators, including the small filters. Last week I spoke to the mechanic about the problem I was having and he recommended a couple of things I should try next time I drop it in the water.

First; to start both engines and run for a few seconds before the boat goes in the water. Something to do with fuel tank pressure causing the carburator to get flooded. Second, once in the water to let the engine cover open and look for water being sprayed over the carburators.

I have not done either one of them. I discovered, after washing the engine compartment, that both front engine mounts where broke on, of course, the right engine. After removing the exhaust manifold I began working on the mounts. As I was wrenching around I noticed a fairly thick black cable broke off from somewhere under the engine. After tracing the cable I realized it was the ground cable that attaches to the starter bolt.

I replaced the mounts and re-installed the ground cable. Started both engines and they sounded good. There is a good possibility the ground cable was not doing a good job at grounding and could have caused the spark plugs to miss occasionally. I guess I will find out next weekend when I drop it in the water.

[fialoe]

Credit where credit is due. Rickster said that ages ago
Nonetheless, all help I am sure is greatly appreciated and I would be delighted to have all that help too. Good to hear your boat will be dooing the rounds again soon.
Well done guys.
Brian