No tell-tail once on plane

Joined
Apr 4, 2022
Messages
6
I have scoured the internet now and haven’t seen the same issue encountered that wasn’t a motor positioning issue so I’ll ask it here.

I have a 2018 75HP Mercury four stroke on a 2018 Bayliner e16 (factory engine). I’ve owned the boat for a few years never had an issue getting a tell tail at any speed. Two weeks ago when leaving the dock the engine put itself into smart gaurd mode shortly after getting up to around 4000 RPMs on plane, when I turned around to look at the motor I noticed the tell tail had sputtered and stopped. Once I brought the motor back down to idle the tell tail returned with excellent flow. Happened a few more times on the way back in to the dock. A guy gave me a can of wd40 to spray into the water intake and this totally fixed the issue completely but I played it cautious and pulled the boat from the water and changed the impeller and gaskets.

Put the boat back in the water after changing the impeller and it ran fine, drove the boat for a week almost every day pulling kids on the tube and cruising up river full throttle without any issue.

Until yesterday when going out after letting the boat sit a few days the same behavior re-emerged. This time the Wd-40 trick didn’t help. I tried backflushing the motor using a fresh water hose we have at the dock for a few minutes and it didn’t help either.

Again, tell-tail TOTALLY PRESENT AND STRONG AT IDLE AND LOWER RPMs. Only cuts out when up and moving on plane. I’ve ordered a whole new impeller and housing and thermostat although I don’t believe they will make a difference as the thermostat wouldn’t impede water flowing through the tell-tail and the impeller housing was in great shape when I checked it just the other week.
FYI I don’t believe this motor is equipped with a poppet valve.

Anyone encounter a similar issue? Totally stumped here.
 
Joined
Apr 4, 2022
Messages
6
I replaced the impeller again in addition to the entire pump housing and seals (none of which looked bad. I also replaced the thermostat and while everything was apart I flushed out the back flush with compressed air and water as well as the tell-tail hole. Put it back on the river yesterday and it ran fine without any issue. Strong tell tail the whole time.
 

airshot

Vice Admiral
Joined
Jul 22, 2008
Messages
5,164
Probably some crud or a piece of an old impellor blade got stuck in the cooling system somewhere. Glad you have it fixed, and thanks for letting us know you found your problem !!
 

QBhoy

Fleet Admiral
Joined
Mar 10, 2016
Messages
8,343
On my mind is to add, there is a water strainer on the top of the engine. Can get blocked up. Usually has an effect on the fuel pump cooling first though.
Also heard reports recently about the flushing port losing seal and badly passing water out it, when under way.
Can I ask if it’s certain that it’s not a result of a poor engine height set up ? Have you seen the mercury service bulletin released a while ago, regarding their revised findings and advice around height adjustment for these particular engines. If it’s the 2.1l engine I’m presuming it is ? I have the 115 version if so.
 
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