1989 Force 125 runs too cold

[mx216]

Okay guys here is what i have. i have tried to read up on it a ton before resorting to this and bothering you guys. 1989 force 125 1258f9b on a 1989 bayliner cobra. my dad bought it new in 1990. In about 2001 pulled the boat out for the year and it sat overnight and someone stole the lower unit. A shop here in portland, OR installed a new lower unit, heres the fun, supposedly it is a newer mercury lower unit that they said would work fine. Ever since then the boat would not stay warm if running at more than about 1/4 throttle. My dad parked the boat and sold it to my cosuin a few years later. First time he took it out he seized the engine. Bought a rebuilt powerhead and the boat is still doing the same thing, will warm up at idle but as soon as youre moving the temps drop way down below 100 degrees. Now i have the boat back from my cousin and trying to get it up and running correctly. Weve had the lower unit off and it does look like everything is the same as a force as far as i can tell from microfiche pictures. This is my first boat ive ever worked on so from all the reading i heard the only thing that cause an overcooling issue is the thermostat being stuck just wide open, definitely not my problem in this case. I have multiple 130 degree thermostats and have tried changing them out. I dont wanna buy a new force lower unit if that is not my problem, but thats where im leaning because this all started right after that lower unit swap. This is a very odd problem to me as i could find nothing about it happening to anyone else, any help would be much appreciated. Thanks guys

 

[roscoe]

Re: 1989 Force 125 runs too cold

Welcome to iboats.

I can't in any way see how this could be caused by the lower unit.


Do you have all the parts installed with the thermostat?

There should be a gasket, then a grommet, the thermostat, a large spring, then the cover.


Click photo to enlarge.

 

[mx216]

Re: 1989 Force 125 runs too cold

Thank you for the reply. I have verified that the thermostat is installed correctly and just checked the thermostat in hot water to verify operation. In addition i have tried other thermostats in it also, all new items. Is there a possibilty of an engine cooling system issue allowing the coolant to bypass the thermostat in any way?

 

[Frank Acampora]

Re: 1989 Force 125 runs too cold

All the lower unit does is pump water to the block--look elsewhere for the problem. Water constantly flows through the exhaust chest and block. The thermostat allows water to run through the head when it opens. Actually, there are weep holes in both block and head so a small amount of water constantly runs through. When open, the thermostat allows much more flow through them.

How are you determining temperature? A gauge with sender on the block? Check the gauge or sender for function and accuracy.

Feel the block and head. 100 degrees will be only very slightly warm to the touch. Proper temperature will be uncomfortable to the touch but not hot enough to burn immediately. Feel the water coming out the idle relief holes in the back. If it is hot to the touch, your engine is not running cold.

 

[mx216]

Re: 1989 Force 125 runs too cold

I must say i have not personaly put the boat in the water. I am going off of what my father saw and my cousin was told by the marine shop that installed the new powerhead. They said the original engine blew up due to cold seizure. I am running the engine on muffs currently. Should i be doing these readings on the water? I am using an infared gauge and an onboard gauge to check the temps. Onboard guage is installed at the thermostat The onboard guage shows 135 at idle and the infared shows 128 on each inner cylinder and 124 on the outer cylinders measured next to the spark plug. The dual upper exhaust holes have hot water coming out at idle but i can hold my hand under them. As soon as i rev the motor the temps drop significantly. the onboard guage shows about 75 and the infared backs that same change in temp. I am reving the engine to approx 4000 rpm in short bursts and it take only 3 or 4 short bursts for the temps to drop that far. Then i let it idle and climbs right back up to 135 in about 30-45 seconds. The exhaust cover gets hot to the touch at idle but goes cold during the engine revs. thanks for the help guys, i am a super newbie to boat engines and dont wanna blow up and have to buy another engine. Thanks for all of the help

 

[Frank Acampora]

Re: 1989 Force 125 runs too cold

Well, there you go! Of course at idle the exhaust cover will first be hot then get cold. Water is always running through it and around the cylinders. Gunning the engine with no load you are developing the RPM but not using nearly as much gas as under load on the water. Think about it: You are using way less than half the gas, developing way less than 1/2 the power, not developing much waste heat, yet pushing through all the water the pump can deliver. Of course it is going to get cold.
The real test is what temperature does it attain upon continuous running on the water at partial to full throttle conditions.

By the way: Get a new mechanic or marine shop. There is no such thing as "cold seizing." These engines only seize up from lack of oil or overheating. They melt pistons from lean running. So, either they don't know or didn't care to explain properly to you. Either way, you don't want to deal with them. I absolutely detest when a service shop tries to BS a customer with little knowledge. Just because they don't know doesn't mean they can't understand if properly explained. Sure it takes a little extra time, but they are taking your money. You deserve better treatment.

 

[mx216]

Re: 1989 Force 125 runs too cold

Thank you very much Frank. I appreciate your help greatly. I am a local pro motocross rider and have done all of my own bike work for the last 12 years. In dealing with two strokes at the track you hear people start their bike and rev them freely without warming up. What we run into is the piston will expand before the cylinder and stick the piston and you will get symetric seizure or a 4 corner seizure on each side of the intake and exhaust ports. So hearing that statement from a boat shop made me leary of running it if that can happen. Im assuming these motors are setup much different even due to the fact that that its states 85 octane fuel . (all of my race bikes are strictly leaded 110) From reading i know the force motors are not highly sought after, but still i cannot afford a new one at the moment . I am just trying to cover my bases and appreciate the help. Fortunately it sounds like that that shop is no longer in business. This work that had been done was quite some time ago and i tried to contact them about the mercury to force bottom end swap, that is when i found they no longer existed. The boat did have some other issues such as the carbs and what not from sitting for so long but i did full rebuilds and went through everything else to make sure it was in working order and it seems to run great out of the water. Again thank you very much and i will let ya know how it goes tomorrow afternoon. Have a good evening. Joel

 

[Frank Acampora]

Re: 1989 Force 125 runs too cold

Well, now I can understand why you are leery but you are comparing a water cooled engine to an air cooled engine and , I suppose, comparing a relatively massive 3 inch diameter piston with a heavy crown to a smaller, lighter, flat topped one.

I don't know about bike engines, but the outboards are made with cam ground or oval pistons. They have a major and a minor diameter to account for uneven heating and cooling. They are much smaller in diameter at the ring land than at the skirt. In the Force engines, pistons are set up "rattle" loose when cold and you can rock them in the bore at least 30 thou. These engines are very old school cross flow engines with a piston baffle. Because the gas charge burns relativly non-turbulently and therefore slowly, (slower than a loop charged engine with a hemi combustion chamber and "squish band") they require 30 degrees timing advance at full throttle.

They are at maximum, only about 155 PSI compression ratio which translates to about 9 to 1 so premium fuel is not required.

Do not run carbs too lean. At the top of the forum page find the sticky--FAQS and read synchronizing carbs and timing.

 

[fucawi]

Re: 1989 Force 125 runs too cold

Racing engines like in F1 race cars are siezed when cold and must have hot water circulated before they can be rotated...the clearances like on your racing bike engines are much tighter than in an outboard so in essance your mechanic was talking rubbish and as usual Frank was right .

 

[mx216]

Re: 1989 Force 125 runs too cold

Alright i have good news, she ran great aside from one little hiccup. Thank you for all the info. I followed the tuning step by step and set my static timing at 28 degrees because i was unable to take the borrowed timing light on the water. (I read in some other posts to set about 2 degress short if you are cranking with the starter at wot) Just one more question about the setup. It just barely doesnt want to idle at zero throttle, my idle adjustment screw is turned in all the way and i have no more adjustment as it is bottomed out on the lock nut. As soon as i use the throttle without engaging gear it idles great, i barely have to give it any at all. I was able to run up 5550 rpm at 45 mph, pulls strong out of the hole and runs incredibly smooth, until i want it to idle in plain neutral with zero throttle. Thanks again as i wouldnt have been able to do this without you guys.