How JustAnswer Works:
  • Ask an Expert
    Experts are full of valuable knowledge and are ready to help with any question. Credentials confirmed by a Fortune 500 verification firm.
  • Get a Professional Answer
    Via email, text message, or notification as you wait on our site.
    Ask follow up questions if you need to.
  • 100% Satisfaction Guarantee
    Rate the answer you receive.
Ask Dominick Your Own Question
Dominick, Marine Mechanic
Category: Boat
Satisfied Customers: 1009
Experience:  25 Years Experience as Mechanic, 20 Yrs Boat Yard Owner/Mechanic, Factory Certified
Type Your Boat Question Here...
Dominick is online now
A new question is answered every 9 seconds

The engine starts missing when the rpms are increased to

Customer Question

the engine starts missing when the rpms are increased to over 2700 or so. dosent want to get up and go. its like a rev limiter almost. changed out the thermostats and sensors and installed new pump and flushed out the water system. i finially got it up on plane yesterday but in severly misses at WOT. what should I check next?
JA: Sometimes boat issues seem like they'll be really complicated, but end up being easy to fix. The Marine Mechanic I'm going to connect you with knows all the tricks and shortcuts. Is there anything else the Marine Mechanic should be aware of?
Customer: The boat run fine before this problem started. the water level on our lake is really low now and I know I sucked up some sand or muck and made the engine over heat a little bit. I know the water systems is clear now
Submitted: 7 months ago.
Category: Boat
Expert:  Charles replied 7 months ago.

Hello, my name is***** will assist you.

What engine are you working on?

Customer: replied 7 months ago.
98 Johnson 200 venom
Expert:  Charles replied 7 months ago.

Thanks, ***** ***** have the full model number from it?

Customer: replied 7 months ago.
I left my info on the boat. I know the last 3 characters were even. Does that help?
Customer: replied 7 months ago.
Expert:  Charles replied 7 months ago.

Let me see what I can locate with that.

Expert:  Charles replied 7 months ago.

Ok, have you checked for spark using a timing light when the engine is misfiring?

Customer: replied 7 months ago.
Customer: replied 7 months ago.
I have run the engine on muffs and it runs great and doesn't sound like it's missing at all. When it's in the water under load is when the issue occurs.
Expert:  Charles replied 7 months ago.

How hot and for how long was the engine?

When was the last time that it ran correctly?

Customer: replied 7 months ago.
The engine got hot while idling through shallow water through the canal on the way to the lake, running for maybe 3 or 4 minutes. Tried to accelerate once I got into the lake but it would not go over 2500 rpms. It got hot enough to melt the threads on the heat sensor retaining nut (plastic) on the starboard side of engine. It also deformed the nipples of both thermostat covers. I noticed this because of water leaking out of the nappies. I replaced nappies, thermostats and heat sensors. Replaced water pump also. The boat ran fine prior to this event.
Expert:  Charles replied 7 months ago.

Ok, before we get too far into this, you are going to need to do a compression test to make sure that the block is still ok.

Customer: replied 7 months ago.
If there were galling of piston rings against the cylinder walls wouldn't the engine be making odd noises? This motor purrs at idle right now. I will do this comp. check but I'm quite certain there is no damage to the cylinder walls or piston rings. I have had that problem before and know how that sounds. For this discussion can we assume the compression is fine?
Expert:  Charles replied 7 months ago.

The engine would not really need to be making any odd noises to have a bad cylinder. You are also going to need to pace it under a load, on the trailer, backed into the water and placed in gear, and bring the RPM up to where it begins to break down, then use a timing light to make sure that you are still getting fore to all 6.

Customer: replied 7 months ago.
OK, after I do your prescribed tests can I just respond back the this thread to continue the conversation?
Expert:  Charles replied 7 months ago.

Yes, you can reply back here. There are no time limits here.

Related Boat Questions