See full version: 1987 Yamaha 90 HP90ETLH
RPM Information: 5500
Your engine's RPM range is important in choosing the right propeller for a given application. For example, if you look at your tachometer at top speed and it is not within the engine's RPM range then that is generally not good. You want your RPM's to be within the proper range while at wide open throttle (WOT). Be sure to do your testing under your normal boating conditions and with a good propeller (not bent, cracked, or excessively chipped).
The iboats Outboard Motor Forums are another excellent source of information.
[links]
This rebuild kit is designed for use with Yamaha 75/85/90 HP 3-Cylinder Powerheads. The kit includes the following:
Six Rod Bolts
Three Pistons [Complete with rings, pins, and clips]
One Gasket Kit [including 1 Head Gasket, 1 Head Cover Gasket, 1 Base Gasket, 2 Reed Gaskets, 3 Carburetor Gaskets, 2 Exhaust Cover Gaskets, 1 Upper Crank O-Ring, 1 Lower Crank O-Ring, 3 Carburetor O-Rings, 3 O-Rings, 1 Fuel Pump Gasket, 1 Thermostat Gasket, 1 Upper Crank Oil Seal, and 2 Lower Crank Oil Seals]
Need advice on finding a used powerhead or a rebuilt one for my sons little 90hp 2 stroke. Everything else is in perfect order except for the low compression on the bottom cylinder.
I'd pull the head and see what the cylinder looks like (scored, maybe a blown head gasket, etc). Costs ya 45 minutes maybe, There are plenty of shops to which the block can be sent for a repair. Many would prefer to have their stuff rebuilt as opposed to buying someone else's used crap with no history of it..00 investment.
Maybe peek in the exhaust port at the rings. [links]
Yamaha 6E7-11631-00
Yamaha 6E7-11631-00-97
Sierra 18-4135
Mercruiser 761-7982T
Mercury Marine 761-7982M
Specs
Piston Kit
Application Internal Engine System
Compatibility Mercury Marine Yamaha Outboard
Type Pistons/Piston Kit
CRANKSHAFT PISTON KIT (Complete Assembly) that fits YAMAHA OUTBOARD 9.9 & 15 horsepower (2 Strokes) – 1984-2006 Later engines.
Piston Diameter: 56mm
Piston Height: 58.75mm
Wrist Pin: 14mm
Engine: 2 Stroke
(Kit includes Piston P/N 6E7-11631-00-97 Rings P/N 682-11610-01-00 & Wrist Pin P/N 634-11633-00 )
Piston Kit for Yamaha 6E7-11631-00 Yamaha 6E7-11631-00-97 Sierra 18-4135 Mercruiser 761-7982T Mercury Marine 761-7982M
Fitting Yamaha 9.9 / 15 Hp PISTON ASSEMBLY (56mm) Application Internal Engine System Mercury Marine Yamaha Outboard [links]
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