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97 force 75 hp loss of RPM's

T

trebor433

New member
Have a 97 75 hp motor. It was running fine would RPM up to 5200 no problem. Now it gets to 4600 and that is it. Replaced fuel pump and hose. No change. Replaced the plugs. Noticed that top 2plugs had milky look. Haven't checked compression yet but will. Idle is also not as good as previously. It does start fine.
Any help and suggestions would be appreciated.
 
Jerryjerry05 said:
If your plugs have a milky look then your head gasket's gone bad.
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I am hoping that it is the head gasket. I have been running it and hope it is not damaged. I wonder if it will show up with a compression test. The plugs are definitely milky I am an old hot rodder and unfortunately have seen that before. Wonder will I be able to get the bolts out? Fresh water only, in good shape.
 
Just be careful when removing the head bolts.
They are only in with 19# of torque.
They get corrosion around the main part of the bolt.
The threads are usually free but the shaft of the bolt and the aluminum head corrode and the corrosion seizes the shaft.
I use a small torch, WD or PB Blaster and a hammer.
I spray, heat and tap, then repeat.
 
Jerryjerry05 said:
Just be careful when removing the head bolts.
They are only in with 19# of torque.
They get corrosion around the main part of the bolt.
The threads are usually free but the shaft of the bolt and the aluminum head corrode and the corrosion seizes the shaft.
I use a small torch, WD or PB Blaster and a hammer.
I spray, heat and tap, then repeat.
Click to expand...
Got time to work on motor. Thought it had a blown head gasket for sure. Plugs looked milky I thought. Did a compression test and all cylinders had 125 lbs. Did a leak down and all 3cyls were at bout 4%. Attempted to check spark strength. Still trying to figure out why rpms are down bout 600 at WOT?
 
Jerryjerry05 said:
If you have water on the plugs?? Then there is a problem.
I had a gasket go bad and still had 145# on all 3 cyl.
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I am going to check the timing this weekend and if it is ok guess I will look at the plugs one more time. I know the top two look wet to me. I just hate to fight with the head gasket and it not fix the problem. If I was positive I would not hesitate. I greatly appreciate the response and any info. If I don't find anything else I guess I will order gaskets.
 
trebor433 said:
I am going to check the timing this weekend and if it is ok guess I will look at the plugs one more time. I know the top two look wet to me. I just hate to fight with the head gasket and it not fix the problem. If I was positive I would not hesitate. I greatly appreciate the response and any info. If I don't find anything else I guess I will order gaskets.
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Took head off. Top two cylinders wet with water. No visible evidence of water leak past gasket. Cleaned everything. Reinstalled with new boats. Still have water on plugs. Where else could it be coming from?
 
I'm having the same exact problem with my 97 75hp force I replaced head and exsulst gaskets with no luck if you find the problem please let me know. I would not wast my time with the exsulst gaskets 50% of my bolts broke and it was crazy trying to get them out. When I pulled it off the gaskets and plate looked great. It was a wast of time and money for me.
good luck
 
Fishing123 said:
I'm having the same exact problem with my 97 75hp force I replaced head and exsulst gaskets with no luck if you find the problem please let me know. I would not wast my time with the exsulst gaskets 50% of my bolts broke and it was crazy trying to get them out. When I pulled it off the gaskets and plate looked great. It was a wast of time and money for me.
good luck
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After some thought I realized that maybe I had over looked something. So I took the head back off and checked the gasket and the surface of the block. The block was low at the cylinders. I took my time and resurfaced the block with a straight edge that I made at work. Put a couple of coats of copper coat on the gasket and reinstalled. When torqueing the bolts they felt much better. The catch is I have not started it yet. I think it is fixed. I should find out this weekend. If it is not fixed I am not sure what is next.
 
Did this fix your problem I have all but split my engine to find what is going on please let me know it worked so I can order a new head gasket and start resurfacing. thanks for the last update gave me some hope. Good Luck
 
Fishing123 said:
Did this fix your problem I have all but split my engine to find what is going on please let me know it worked so I can order a new head gasket and start resurfacing. thanks for the last update gave me some hope. Good Luck
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I didn't get to try it this weekend. It is at my camp house and we did not get to go this weekend. I am sure I will get to go this next weekend. I feel real good about it. Keep fingers crossed. I will let you know.
 
trebor433 said:
I didn't get to try it this weekend. It is at my camp house and we did not get to go this weekend. I am sure I will get to go this next weekend. I feel real good about it. Keep fingers crossed. I will let you know.
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Still has water on one spark plug and will only run about 4000 RPMs under a load. I have no idea what to do next. Maybe someone will have a clue. This motor is in good shape otherwise. Maybe I will just sell it. Surely someone has had the same problem and knows the answer.
 
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