Problem 2007 Yamaha Jet boat

[Juan Negron]

Hi everyone I just join the the forum and I wanted to see if anyone had a problem with a jet boat with the same problem I have. My right engine starts to surge and won't go past 7500 RPM the engine doesn't die it just loses total power! then the boat runs just on the total power of the left engine! Any suggestions?

 

[Bruce]

Most likely you need to change the spark plugs. I change them every year to avoid this issue which happens when the plugs get dirty.

 

[Bruce]

Forgot to say Welcome Aboard.

Oil is unlikely to be a contributor to this issue but spark plugs, oil and filters should be changed once a year.

 

[Juan Negron]

Forgot to say Welcome Aboard.

Oil is unlikely to be a contributor to this issue but spark plugs, oil and filters should be changed once a year.

Thanks Bruce I will start with changing the plugs!

 

[itsdgm]

Welcome @Juan Negron to JB.net. I agree with Bruce. Start with the spark plugs and report back.

 

[Juan Negron]

Thank I will do!

Welcome @Juan Negron to JB.net. I agree with Bruce. Start with the spark plugs and report back.

 

[4x15mph]

Are you saying that the engine revs at 7500 rpm and can stay in that range or does it peak there and then drop below a lower RPM number????

If the engine is revving normally (i.e. 7500 RPM+), double check that you are not experiencing cavitation on that starboard/right pump. Are the blow out plugs in tight and are you sure there isn't anything stuck in the impeller? Check and double check.

 

[Cobra Jet Steering LLC]

By chance is your problem engine overfilled with oil? if so it will ruin your air filter and cause the engine to do as you described. Inspect your air filter element and oil level.

 

[Juan Negron]

Are you saying that the engine revs at 7500 rpm and can stay in that range or does it peak there and then drop below a lower RPM number????

If the engine is revving normally (i.e. 7500 RPM+), double check that you are not experiencing cavitation on that starboard/right pump. Are the blow out plugs in tight and are you sure there isn't anything stuck in the impeller? Check and double check.

Check the Impeller and is ok! I took out the boat 6 times every single 1st day of launching the boat ran fine! There was several months before launching because the boat is in Puerto Rico, However, the following day it doesn't want to go over the 7500 RPM and get the maximum out put of the engine! It doesn't die at that point but the max RPM I can run at is at 7500 RPM if I engage full throttle it doesn't pick up the power!

 

[Juan Negron]

By chance is your problem engine overfilled with oil? if so it will ruin your air filter and cause the engine to do as you described. Inspect your air filter element and oil level.

Check that all good!

 

[Scuba_ref]

One time when I was messing around on the engine I forgot to reattach one of the Ignition Coils back on top of the spark plug which meant that only 3 of the 4 cylinders were firing. Didn't realize it until after running the boat and noticing that I was only getting about 7500 rpms instead of the usual 10,000 on that engine.

 

[Juan Negron]

One time when I was messing around on the engine I forgot to reattach one of the Ignition Coils back on top of the spark plug which meant that only 3 of the 4 cylinders were firing. Didn't realize it until after running the boat and noticing that I was only getting about 7500 rpms instead of the usual 10,000 on that engine.

I will definitely take a look at that also!

 

[ToddW850]

Welcome to the Forum! I agree with all the above. Also, changing spark plugs on these boats seem to change the world. Keep us updated and we will get this figured out.

 

[Juan Negron]

Thank you very much!

 

[Scottintexas]

Glad to have you on board,
How long have you owned the boat? Have you changed the spark plugs before?

I agree that spark plugs are a good and easy place to start. Check out the FAQ for lots of great info and be careful removing the #3 plug as it has a history of becoming seized and can easily snap off, use anti-seize when you put the new ones in.

 

[Juan Negron]

I have the boat for about 1 1/2 years I bought it with that problem in hand and I haven't replaced the spark plugs yet. However I will be in PR and will be replacing the plugs and will carefully take your advice also! Thank you and I'm glad to have join this forum!

 

[SCSTWG]

Welcome to the forum. If you take a logical approach to this and report back with accurate information, I guarantee the folks on this board can solve your issue. The added benefit is that it will be less expensive and faster than taking it to the dealer.

 

[Juan Negron]

I will report sounds like I will get the right information here that's for sure!

 

[Juan Negron]

OK my friends, I changed the Spark plugs It made a great difference. The engine didn't drop in RPM but know the drive shaft for the impella is slipping is winning but going no where! I changing the Drive shaft and the Mid shaft. Should I just buy OEM or after market parts? Thank you for all your advise!

 

[ToddW850]

Great! Now make sure your clean out plugs are in. That could be why you're not going anywhere. However, if they are in, then we have another issue.