90hp force -what year model,rpm,prop size

ferg57

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Sep 9, 2004
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i have a 90hp force ser#oe123251 what year,what rpm,what prop size for 24ft starcraft pontoon.any help is appreciated.
 

roscoe

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Oct 30, 2002
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21,657
Re: 90hp force -what year model,rpm,prop size

Looks like a 1995.<br />rpm range 4750 - 5250 rpm at wide open throttle.<br /><br />The prop needs to be selected so that the motor will attain the suggested maximum rpm range. <br />This doesn't mean you have to operate the motor at full throttle, but ensures you have the correct prop to balance the load or resistance on the engine.<br /><br /> click to read more <br /><br /><br />So the questions are:<br />What diameter and pitch prop are you now using?<br />What are the maximum rpm's you achieve at full throttle, using this prop?
 

ferg57

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Re: 90hp force -what year model,rpm,prop size

roscoe first let me say thank you for your time an knowledge,i have looked every where for the year model with no luck untill now.its almost like it was some huge secret and what i can not understand is,do i have a force or a merc,what parts are merc an when asking for parts do i just say 1995 3cyl 90hp merc. now let me try to answer those questions you asked.at wot rpm 5400-5500, i do not run it wide open any way,some where around 4500-4800 im at the lake so whos in a hurry! i do not know what dia or the pitch of prop would be. if you would be so kind,as to answer one more question. i have a 130 degree thermostat- temp at above rpms runs around 140-145, would this be with in the normal range, thank you.
 

roscoe

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Oct 30, 2002
Messages
21,657
Re: 90hp force -what year model,rpm,prop size

Mercury bought Force from the USMarine bankrupcy sale in 1989?. They kept the Force product line and name to provide an economy line of motors. But they also knew they needed to upgrade the Force components to make them more reliable.<br /><br />The surefire way to verify you have a 1995 model, is to look at the lower unit, directly above the prop. If you have a small flat trim tab, round disc with a fin pointing downward, you have a 1995 or newer.<br /><br />If you have a large hollow fin, which is called an exhaust snout, you have a 1990-1994 model.<br /><br />The 1995 model would have a Mercury lower unit, charging and ignition system, lots of little parts, a Merc tilt and trim unit, and upgraded carbs I think.<br /><br />You can get most if not all parts from a Merc dealer.<br />Always supply the dealer with the model number when ordering parts.<br /><br />No Merc dealer where you are located? Then you can order them directly from Merc at www.MercuryPartsExpress.com<br /> Or from www.MercruiserParts.com ( the same Mercury parts at a 10% discount )<br /><br />The prop you have is allowing the rpm to go a bit high, but it is not too bad. Afterall, you are pushing a pontoon and the extra thrust is nice. IF you need to replace the prop, you might want to increase the pitch by one inch. But you should be ok as is. You will Not get better performance by changing the prop, unless yours is severely damaged.<br /><br />130* is the temp at which the thermostat opens, so it is not unusual for the motor temp to be slightly above this. Did you actually inspect the thermostat to see if it is a 130*?<br />Someone might have put a 143* therm in by mistake.<br /><br />Change the waterpump impeller annually, and decarb the motor every fall, and it should be good.<br /><br />Click and read this: http://www.iboats.com/cgi-bin/ubb/ultimatebb.cgi?ubb=get_topic;f=36;t=000016 <br /><br />These motors are pretty basic and easy to work on, well, except for syncing the carbs.<br /><br />Known failures are the impeller causing an overheat .<br />I have a Water Pressure gauge on mine, as it will indicate the drop in water pressure immediately. Where the temp gauge will only tell you of an overheat AFTER it gets too hot. So keep a close watch on that gauge.<br /><br /> <br />And the original stators would fail causing the ignition to die.<br /><br />Happy Boating. May your Force live a long and healthy life.
 

ferg57

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Sep 9, 2004
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Re: 90hp force -what year model,rpm,prop size

roscoe you are a GODsend and i cannot thank you enough.i do have a 130*thermostat installed new last year also new impeller.i asked local dealer about pressure guage he said no bigger than the motor was there would be such a small amount of pressure that it would not tell me much.this is the reason for temp gauge.where would suggest buying pressure gauge at and should it be hooked up same place as sending unit for temp gauge. the reason for all of this is high temp buzzer kept going off,could let motor idle for little bit buzzer would quit,go 3/4 throttle run fine,go 7/8 throttle buzzer go off again.this is a new boat to me at least dont want to burn up my motor 24ft of boat to much for wife to haft to paddle.so i replaced everything but the wife,take the boat back to the lake[180mile round trip]run boat till the buzzer goes off again then pull the cowling off and while she drives i use a raytek non-contact thermometer to take temp readings all over the motor, the cover for the thermostat read 135*.that is why i installed temp guage. i believe small sensor that is resessed in the water jacket is bad.local dealer cannot or will not find one of those for me either. if it was a high powered bass boat it might be a different story,but alas i am [forced]to go this route,which i am proud to say,is fine with me. have a great weekend.i think iwill go buy my wife a new paddle just in case..
 

ferg57

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Sep 9, 2004
Messages
27
Re: 90hp force -what year model,rpm,prop size

roscoe just looked at the web sites you recomended what would i ever do with out you. found everything i was looking for and then some in 5 min.thank you-thank you-thank you
 

roscoe

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Oct 30, 2002
Messages
21,657
Re: 90hp force -what year model,rpm,prop size

You can get a water pressure gauge kit from right here on iboats, in the MegaMall.<br /><br /> http://www.iboats.com/mall/index.cg...tegory=water pressure gauge&*******=327400861 <br /><br />The kit includes everything you need to install, except the hole cutting saw and a little bit of teflon pipe seal tape.<br /><br />If you shop the web a little, you might find some that match your current gauges.<br /><br />You should have a small screw in pipe plug in the top of your motor, just above the thermostat. Remove the plug, insert supplied fitting, attach plastic tubing, run the tubing up to the gauge, and connect the lighting wire to your other gauges if you like. Done.<br /><br />My gauge reads approximately:<br />4psi at idle<br />9-10 psi at cruise<br />and 14 psi at full throttle<br /><br />If I ever see it read less than these numbers, I know something is wrong. ( either a blocked water intake or a bad impeller.)<br /><br />Ain't the internet great.!!!
 
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