93 Yamm 115 - new impeller and thermostats now hot over 4000rpm

[scottfromoz]

Hi fellas - 500 hour motor. Always been a great bit of kit. Just had a full service 3 months ago and have not run it since (warm climate - no ice etc) - new thermostats, impeller kit, seals, plugs etc. I took it out for the first time yesterday and it had a strong tell tale at idle and up to about 3000 rpm and then I thought it was a little different at above those revs and not quite normal...heat alarm went off and motor cut 2 cylinders and after idling for only 3 seconds or so the heat alarm went off and i had full power back. I went back on the plane again and its fine at 3500 rpm, but creep up to 4000 or over and within a minute of so the heat alarm goes off again. Keep it under 4000 and she goes all day (which I then did). The **** tale is still strong at above 3000 but seems to stutter a tiny bit..hard to describe.

I assume that my new impeller is damaged.....any ideas?

Cheers

 

[gss036]

Re: 93 Yamm 115 - new impeller and thermostats now hot over 4000rpm

I don't know much about Yamaha's but I would suspect that your "poppet valve" is stuck closed or blocked. They are designed to dump excess water at higher RPM. Usually about 3000 rpm.

 

[scottfromoz]

Re: 93 Yamm 115 - new impeller and thermostats now hot over 4000rpm

Thanks matey. I think the stuttering of the tell tale was the effect of the wind - the extra wind at 50kph compared to 30 kph say. In the tank today the tell tale was strong through the rev range, but in the mid to high 3000 rpm - 4000 rpm (I didnt go higher) she was pinging....I have totally fresh fuel in her so perhaps the timing is out from a dodgy coil pack or something like that?

Cheers

 

[rodbolt]

Re: 93 Yamm 115 - new impeller and thermostats now hot over 4000rpm

that high RPM no load ping is not a ping but the roller bearings hammering on the journals.
2 strokes love RPM just not no load RPM.
if this is a saltwater motor your describing a scale buildup in the water jacket.
a defective poppit normally shows up as an overheat at low speeds, as does an air leak at the pump plate due to corrosion build up in the rubber dam pocket.
if the pocket was cleaned,the wear plate,impeller, and insert were replaced then most likly your going to be looking at head gasket and water cover removal to clean the scale.

 

[grid]

Re: 93 Yamm 115 - new impeller and thermostats now hot over 4000rpm

Rodbolt and I are sitting here waiting for pieces of engine to be airmailed our way! A little thought here: if you'd had this service done to your car, and a problem developed immediately upon using it, what would you do? If it were mine, I'd return it to the dealer and get him to stand behind what he did--and I paid for! Is there a difference with your boat? Shouldn't be. You brought it to him in good shape, just needing X, Y, and Z, and you get it back with problems, if I read you right. If you did the work, one thing I'd look at would be the sealing o-ring under the impeller housing. At upper RPMS that can suck air instead of water. You could also check thermostat operation with a temp gun to eliminate a faulty thermostat.

 

[rodbolt]

Re: 93 Yamm 115 - new impeller and thermostats now hot over 4000rpm

got it serviced 3 months ago and did not run it since? may or may not be anything a dearler did or did not do.
corrosion never sleeps.
kinda like a blowboat customer several years ago, I did the cooling system and rebuilt the carb, two years later he is in complaing, seems he picked up the motor,never ran it and lo and behold the pump was dry rotted and the carb was fouled. he thought I should do it again free, he thought wrong.

 

[scottfromoz]

Re: 93 Yamm 115 - new impeller and thermostats now hot over 4000rpm

Thanks fellas. Rodbolt - I only ran it for a couple of seconds at 4000 rpm in the tank, so hopefully I didnt do any damage to the bearings! How do they do it at the dealers...I see they have big heavy steal tanks (portable though) but surely they dont engage drive...so how to they test for missing under load for example. My dealer never water tests unless absolutely necessary...which is about once in 10 years!

It was dealer done and I dont blame him because I know that corrosion works worse when the motor is sitting - I flush it but its a salt water motor.

It could be a dealer problem though and either way Im going to take it back to him I think (I trust him from years of assistance) and let him work it out...will post the results. I remember a mate of mine had a Johhno 115 V4 with identical symptoms...turned out to be corrosion in the water jacket - took covers off and cleaned out with new gaskets and it was all sweet.

Cheers

 

[scottfromoz]

Re: 93 Yamm 115 - new impeller and thermostats now hot over 4000rpm

On second thoughts I might pull the jacket covers off and look to see what its like. If I find corrosion I can clean it out. If I clean off all the old gaskets can I use a formagasket type of goo instead of using the fibre one from Yammy? If so what brand is best?

Cheers

 

[rodbolt]

Re: 93 Yamm 115 - new impeller and thermostats now hot over 4000rpm

NO
use only Yamaha gaskets.
I have seen issues with some aftermarket stuff.
if your gonna remove the water covers ya may as well remove the heads.
its not hard and doesnt require a bunch of tools.
just pay attention to the details,dont use any steel wire brushes and carefully scrape and clean everything.

 

[reeldutch]

Re: 93 Yamm 115 - new impeller and thermostats now hot over 4000rpm

every waterpump we do will be baytested before sending the boat home.

i would find a dealer who baytest the work he does.

you might want to instal a waterpresure gauge so you know if you loose pressure at 4000 rpm.

and i would verify that you are indeed overheating at those rpm's with a temp gun.
Are both banks overheating ?
or just 1 bank

did you install anything else on your boat in those 3 months?
may be a trough hull or transducer?

good luck

 

[scottfromoz]

Re: 93 Yamm 115 - new impeller and thermostats now hot over 4000rpm

Thanks for the replies fellas - appreciate the help. Its got nothing new - nothing for example that might impede or upset water flow around the leg.

Cheers

 

[scottfromoz]

Re: 93 Yamm 115 - new impeller and thermostats now hot over 4000rpm

Someone told me that in their commercial boats they had problems with Yamm V4s overheating at higher revs and it turned out to be restrictions in the fuel line.

I didnt think the following could be related so I didnt post it (I thought if it was not getting enough fuel it would simply not pull the revs!). At the ramp the primer bulb wouldn't pull up the fuel from the front tank. I then switched to the rear tank that provides positive pressure when full and she primed and ran. I ran it like that. Back home in the tank I primed it and it ran, but then slowly died and stopped and when I checked the bulb straight away it was empty....so it seems that either the check valve is stuffed in the bulb or there is a loose hose clamp...will look at both.

I wonder if they pull the revs despite not passing enough fuel for normal running, so they run lean and that causes high temp...?

Cheers mates

 

[reeldutch]

Re: 93 Yamm 115 - new impeller and thermostats now hot over 4000rpm

have you verified the temp of each bank yet?

assuming and guessing aint gonna solve it.
do some basic test and go from there.

first find out witch bank is overheating if it indeed is
and see if at high speed you can get a waterpressure reading with a gauge.
so you know you have adequat pressure or may be not enough.

 

[pine island fred]

Re: 93 Yamm 115 - new impeller and thermostats now hot over 4000rpm

Before you get to involved, go back and check the water pump. Pump liner is eccentric with 2 or 4 ears pressed into the chrome or stainless liner which indexes with the plastic housing. Is possible for the liner to come un indexed when the impeller is installed resulting in a partial blocking of the pump outlet. Results are it pissing like a race horse but not getting full water flow. Just went thru a hair pulling experience with that being the problem. Just might help ? See YAMAHA OVERHEAT FIXED back in november! Maby that is the problem. regards FRED

 

[scottfromoz]

Re: 93 Yamm 115 - new impeller and thermostats now hot over 4000rpm

Thanks fellas - given that my trusted mechanic did the service and this happened first time out after that I took it back to him. Mech reckons it cannot be fuel. He found that a pressure relief valve in the head was blocked and he fixed that up, so he reckons that would have been the cause of the problems and that everything else with the leg off checked out properly. I will test her in the next week or so, but this sounds right - its good when a cause is found.

Cheers

 

[rodbolt]

Re: 93 Yamm 115 - new impeller and thermostats now hot over 4000rpm

on a yamaha V engine, a stuck poppit valve wont cause high speed overheat. as long as you keep it above 2000 RPM you can run without it.
good luck but keep pokin and hoping.

 

[StinkyMako]

Re: 93 Yamm 115 - new impeller and thermostats now hot over 4000rpm

 

[scottfromoz]

Re: 93 Yamm 115 - new impeller and thermostats now hot over 4000rpm

Thanks Rodbolt. Cheers Jax. I will run it and see what happens. Look forward to hearing more about your problem Jax and as to whether its fixed and what fixed it. Cheers

 

[StinkyMako]

Re: 93 Yamm 115 - new impeller and thermostats now hot over 4000rpm

 

[scottfromoz]

Re: 93 Yamm 115 - new impeller and thermostats now hot over 4000rpm

Thanks all. The problem turned out to be the poppet valve. Took it for a good hard run today - 5400rpm for a few miles, 5000 for about 10 mins and 4500 for 15 mins and she didnt miss a beat. Beautiful to start. Idle is great. Love this old girl...Thanks again fellas.

Cheers

PS. They will charge me for finding it - it wasnt part of the service last time around and its not somthing that I would think to check and clean etc (might require a gasket too I guess) so I assume most mechanics wouldnt make it a regular service item.

Cheers