Engine descaler advice needed

[davostephens82]

Hi

Im new here.

I have a 30 hp yammy 2000 model 2 stroke. Good condition, recently the rev limiter has kicked in with overheat. Motor was running good until when over 3/4 revs then rev limiter kicks in. Motor always flushed. So the Mechanic has replaced water pump and impellor, Also cleaned water jackets etc. Now the rev limiter only kicks in at idle after hammering along for a while, I travelled 5 mile flat chat and no problem, neutral and idle getting anchor ready, then take off and rev limit activates, neutral, few revs and increase water flow thru, cools down and away I go... no problem til do the same again.. Water thru the telltale is constant but not like a full jetstream out.

Mechanic is inclined now to remove whole powerhead to inspect the lower galleries, but I can only assume another 500-700$

I am inclined to put starbrite flush descaler through to maybe clear restrictions of scale and mud. Anyone had any experience with this product?

Thanks

[noelm]

Most descale products are for preventative maintenance, once minerals and other stuff harden, nothing will just flush it away, it has to be mechanically removed, I think you might need to do a bit more trouble shooting, was the entire water pump replaced, or just the impeller? check the pressure relief valve (if your motor has one, most do) has the thermostat been replaced?

[JonD]

I use saltaway for flushing my engine ( trailer, fishing gear etc ).  I've heard of concentrated mixes greatly helping such issues, which might be worth looking into before you start pulling things appart. https://www.salt-away.com.au/. 

[jeffb5.8]

Check your thermostat on my Etec once the thermostat was blocked Partially open I would get a temp alarm after coming off a full speed run down the river, like idling to the wharf.

I also used Salt Away and noticed a big difference in my tell tale stream, once the motor was full of Salt Away I left it for 2 weeks and then repeated the process.

Also I used the flushing port (Motor Off) to reverse flush the motor first then put the ear muff and started it to flush both ways.

 

P.s

I replaced both thermostats in my engine as well,

Edited September 16, 2019 by jeffb5.8

[davostephens82]

Yeh new pump housing, new impellor, new thermostat full service and replace anything that could be the issue, Temp probe was put on as rev limiter came on and it was 88degrees, apparently rev limiter/overheat kicks in at 90 deg.

Then water jackets scrubbed/scraped and put head on and new gaskets etc. Also exhaust jacket scrubbed and scraped, then new gaskets and re attached.

Like i said before seems not a full jet of water thru telltale at idle. also not much water through the upper exhaust outlet (fine minute spray) so water mainly comes out at prop end 

This starbrite contains hydrochloric acid. apparently you run some into motor, let sit for 10 mins then run some more through, let sit, then a full proper water flush for 10 mins or more.

Just asking if anyone has had any experience with it.

I  use salt away now for the final rinse before putting boat away for 6 weeks whilst at work. Mechanic got me started on this, sounds fair enough. its a preventative mostly

[davostephens82]

Any had any experience with product out there??

[jeffb5.8]

Not I but interested in how it goes, be good if you had before and after photos or Video even just the water flow from telltale.

[Hoods]

I have a Mercury 4 stroke which is overheating. It pumps water but not enough. The mechanic says the problem is the rubber grommet at the top of the water intake pipe which has a tendancy to swell and blocks the inlet hole reducing water flow. Found this on another site demonstrates the issue - maybe yours is similar. http://www.rib.net/forum/f36/powerhead-removal-35217.html

[rickmarlin62]

My 90 yammie was havin probs  i could run high speed for ages  pullup idle round and alarm would go off   new waterpump housing and cleaned out area of poppet valve and grease smeared on it  solved alarm prob and gave me better flow in telltale