Strange sound that disappears after a few minuets.

[Trooper96]

Noticed the problem when I put the boat in the water fired the engine up without a problem but when applying power the boat would hardly move. After a few minuets the boat was running fine and had no issues getting it up to speed. Now at home I hooked up the mickey mouse ears and again fired the boat up without a problem, but now I can hear a strange sound possibly coming from the back of the engine. This sound disappears after a few minuets and then the engine sounds fine. I attached two videos as the noise is hard to explain. I have checked the Hydraulic pump which appears to be working fine along with all my fluids. Any help would be much appreciated.

Boat Info: 2013 Chapparal H20 Sport.

Engine:
MerCruiser 4.3 TKS
Model: MCM 4.3 LITRE
DOM: 11/11
Engine Serial: 1A658585

Outdrive:
MerCruiser Alpha one
Drive Serial: 2A059296
Drive ration: 1.62

 

[1985 Century Mustang]

My best guess is It sounds to me like your engine coupler is loose. The coupler attaches to the flywheel. The same thing happened to me. I had to lift the engine and tighten the coupler bolts then realign the engine. When was the last time you had it aligned? To trouble shoot, remove your outdrive and see if the noise persists.

This was my issue below.

 

[Trooper96]

My best guess is It sounds to me like your engine coupler is loose. The coupler attaches to the flywheel. The same thing happened to me. I had to lift the engine and tighten the coupler bolts then realign the engine. When was the last time you had it aligned? To trouble shoot, remove your outdrive and see if the noise persists.

This was my issue below.

Sounds fun. I just purchased the boat at the end of last year and have no idea if its ever been aligned. Did the nocking go away as the engine ran or will be be persistent?

 

[1985 Century Mustang]

Sounds fun. I just purchased the boat at the end of last year and have no idea if its ever been aligned. Did the nocking go away as the engine ran or will be be persistent?

Yes mine was persistent when it started making that similar noise, but it didn't the first 3 months when I got the boat. And my boat is 1985 . So, Yours eventually could be persistent. Needless, have a good/qualified mechanic listen to it first, before you think about removing the engine. It wasnt a hard job for me, but getting those rear motor mounts out were on my Mercruiser A1-G1. There's a trick to it if your rear MM bolts are seized.

This is what I went thru.
'Alpha One knocking noise'
https://forums.iboats.com/threads/alpha-knocking-noise-video.764675/post-5849642
And this.

https://www.thehulltruth.com/16375202-post1.html

If you have to remove the engine to address the coupler,,, and your doing it yourself, you can reach out to me, I'll gladly give you some pointers. Good Luck, I hope it's good news. Us boaters could use some good luck all the time.

 

[Scott06]

The hissing noise is the TKS valve in the carb. It should hiss on cold starts until engine gets up to speed.
the tks system uses a enrichment valve to fatten up cold start mixture vs a conventional choke. The whole idea is a work around so folks who have never driven a carburated car dont have to set the choke and prime by pumping the throttle…

 

[1985 Century Mustang]

The hissing noise is the TKS valve in the carb. It should hiss on cold starts until engine gets up to speed.
the tks system uses a enrichment valve to fatten up cold start mixture vs a conventional choke. The whole idea is a work around so folks who have never driven a carburated car dont have to set the choke and prime by pumping the throttle…

Good Call, hope he sees your post. I inboxed him anyways about your post.

 

[1985 Century Mustang]

I youtubed TKS. Is this similiar to your sound?