Suzuki DT-115 overheat help

[John Jones]

I'm kinda running blind trying to help my father-in-law in South Jersey.  He has an old DT-115 (exact year unknown but I do have the full model number).  He says it's overheating or at least he thinks it is.  Anyway, the horn sounds if you get over 3500 rpm.  He is assuming it's the overheat alarm.  He does not have a manual.  He just had a shade tree OB mechanic change out the water pump.  The mechanic told him to change the thermostat before he ran it and he wanted me to order him a t'stat.

My questions are:
1-Is overheat the only reason the horn sounds?
2-I know years ago a buddy's 200 Zuke horn started going off 35 miles offshore and we finally figured out it was the little flapper water flow sensor stuck.  Does the 115 have this?
3-Does a Zuke have a poppit valve to allow higher water flow at high rpm?

Thanks in advance.

[fitz73222]

Good morning JJ,

Knowing the model and serial number would be a big help. Normally, a high speed overheat can be attributed to a sticky poppit or open valve. (Not sure if this engine has one.) The valve actually maintains a consistant water pressure in the block the slows down the water flow and allows the circulating water to collect more heat before discharging. If the water is flowing through the block too fast, it wont collect enough heat and the engine can actually begin to run hot. This was a common problem on older V6 Mercs. A sticking thermostat can also cause this condition. We have to assume that the water pump base plate was correctly sealed when installed and that if the plate or housing was reused it wasn't deeply grooved from sand and is losing water pressure. I'm not sure what kind of oil warning system the engine has to detect low oil or low oil flow. My guess is that this is a cooling problem. Get some engine numbers and we can see whats under the hood as far as water flow goes.

[John Jones]

New info this morning.

I questioned him about the "alarm" he was getting.  He says it is on the "gauge" and he is positive it is the high temp alarm.

He said "Oh, I forgot to tell you.  We pulled the thermostat out and it ran fine without getting an alarm."  Maybe the t'stat is the whole issue.

He says the only markings are DT115651162.  I was hoping he had more info.  He is 80 and not quite as sharp as he used to be.  He has run boats all his life and can overhaul a GMC 6-71 diesel in his sleep but he knows nothing about outboards.  

A few weeks back I sent him the complete water pump kit including housings.  I hope they used all the pieces but I will find out.

He is going to try to find a thermostat today but has not had much luck locally.  Brown's Point Marine in N. Jersey is the only Zuke dealer around so it may take a few days for him to order it from them.  Otherwise I will order it from Boats.net and have it shipped to him.

Let's wait and see what happens with a new t'stat before you waste too much brain power on it.

Thanks a bunch Fitz!

[smitty 1]

John,

I have a 93 DT225 on my 222CCP and I have had T'Stat problems with mines as well. I change them out every 2 years when I change my impeller out now and haven't had a problem since.
Smitty

[fitz73222]

John,

I have a 93 DT225 on my 222CCP and I have had T'Stat problems with mines as well. I change them out every 2 years when I change my impeller out now and haven't had a problem since.
Smitty

Great advice! The problem with thermostats is that many folks don't run the engines long enough when flushing to get them to fully open and clean themselves out. you really need to run them a good 15 minutes to get then to fully open. The issue I have with built in flush attachments on newer engines that don't require you to run the engine is that the thermostats stay closed during the process and completely rot away in as little as year. I'm fortunate to live in a slightly remote neighborhood location that allows me the 1/2 hour plus I need to flush two 115's without Peeing off the entire neighborhood. Bring um some fish every once in a while to keep the peace!

[John Jones]

Yeah, the neighbor behind me in FL would flush his twin merc 150's at 11PM.    

Fitz, I talked to Pop's this morning.  He ordered t'stat and gasket yesterday.  It will probably be late next week before he get's a chance to try it out.  The dealer told him it was a 1996 model.