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  WOT on 1988 Yamaha 90HP

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Author Topic:   WOT on 1988 Yamaha 90HP
bugsyjr posted 08-14-2003 02:58 PM ET (US)   Profile for bugsyjr   Send Email to bugsyjr  
I was trying to figure out what the RPM's should be at on a 90 HP Yamaha Motor on a 88 17' Montauk with out the overheat alarm going off.
Bigshot posted 08-14-2003 04:06 PM ET (US)     Profile for Bigshot  Send Email to Bigshot     
It should never go off....but 5500 is redline. Waterpump is probably going if only overheating at WOT.
bugsyjr posted 08-19-2003 01:38 PM ET (US)     Profile for bugsyjr  Send Email to bugsyjr     
If I cruise at 4200 RPM for 5 minutes or so the alarm starts going off. I guess i will have to have the waterpump checked out.
Bigshot posted 08-19-2003 02:42 PM ET (US)     Profile for Bigshot  Send Email to Bigshot     
Don't check it, just replace it. Lower units on that engine are cake to drop so you can do it yourself or just deliver the foot. When reinstalling check the shift linkage and see if it is rotted just above where it connects to the foot. This lower you do not have to disconnect anything, it literally should just drop out once bolts are removed. If she is a saltwater engine, I bet shift shaft is thin and they get fragile.
bugsyjr posted 08-19-2003 03:21 PM ET (US)     Profile for bugsyjr  Send Email to bugsyjr     
Thanks for the help. Any idea what a new waterpump costs?
bugsyjr posted 08-19-2003 03:22 PM ET (US)     Profile for bugsyjr  Send Email to bugsyjr     
Not a saltwater engine. It only has 300 hours on the motor and has been stored in the garage for the past seven years.
Montauk posted 08-19-2003 03:31 PM ET (US)     Profile for Montauk  Send Email to Montauk     
Waterpump impellers are about $40, and should be replaced at least every two years. Do not run the engine until you replace it. Max RPM for that engine is 5400.
Bigshot posted 08-19-2003 03:36 PM ET (US)     Profile for Bigshot  Send Email to Bigshot     
Unless they changed it my 1990 was 4500-5500 redline. Do NOT buy just an impeller, get the whole kit.
bugsyjr posted 08-19-2003 03:46 PM ET (US)     Profile for bugsyjr  Send Email to bugsyjr     
I will buy the kit before going out this weekend. I'll let you all know how I make out. Thanks for all of your help and advice.
bugsyjr posted 08-19-2003 03:47 PM ET (US)     Profile for bugsyjr  Send Email to bugsyjr     
What should i expect to get in the whole kit?
Bigshot posted 08-21-2003 01:55 PM ET (US)     Profile for Bigshot  Send Email to Bigshot     
Impeller, housing, SS plates, gaskets and maybe a keyway. You might not need the whole kit but it can't hurt. Impellers after time form a curve and at higher rpms will not seat flush enough to move the water being they are "formed". The kit will give you new everyhing so you know it is right and none of the housing or base plates are scuffed, etc.
bugsyjr posted 08-22-2003 10:47 AM ET (US)     Profile for bugsyjr  Send Email to bugsyjr     
I bought the kit and started doing it last night but i could not find where to disconnect the shift rod linkage to take the lower unit off. can you point me in the right direction please. Like to finish it tonight so i can be back on the water saturday
Bigshot posted 08-22-2003 11:40 AM ET (US)     Profile for Bigshot  Send Email to Bigshot     
You don't have to disconnect it. It is a short shaft coming out of your lower unit that fits into another shaft coming down from your powerhead. It should unhook when bolts are removed that hold lower unit on. Did you forget the bolt under the trim tab(triangle thingy)?
bugsyjr posted 08-22-2003 11:49 AM ET (US)     Profile for bugsyjr  Send Email to bugsyjr     
So if i understand you corectly. I just need to
1) drain Lower Unit Oil
2) remove the five Lower unit bolts including the one under the plastic thingy. then the lower unit should drop right down. Should I remove the prop as well?
By the way thanks for your quick responses
Bigshot posted 08-22-2003 01:39 PM ET (US)     Profile for Bigshot  Send Email to Bigshot     
No need to remove prop or lower unit oil. I think there is 5 bolts that hold it on and it will just drop, if not something is stuck.
bugsyjr posted 08-23-2003 06:18 PM ET (US)     Profile for bugsyjr  Send Email to bugsyjr     
That did the trick. I just discovered that the seals in the pump base were shot. Unfortunately they did not come with the kit. The whole water pump appears to be in pretty rough shape. I think I am just going to replace the whole waterpump assembly while I have the it apart.
Bigshot posted 08-25-2003 01:44 PM ET (US)     Profile for Bigshot  Send Email to Bigshot     
Kit should be the whole assembly.......housing and all.

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