Tweet
Chandler from Southern New Hampshire here. Nice to be here! I retired last year after a lifetime as an ASE certified Master Mechanic, shop foreman, engineer and manager. I've been boating since '76. I've had Johnsons, Evinrudes, Mercurys, Mercruisers and Crusaders, but never a Yamaha. Recently I had an opportunity to buy a 15 foot RIB powered by a 90hp Yamaha. The boat is a '97 and I assume the engine is as well. Of course the tag on the engine is in tough shape. The only thing I can see of the model number is B90 but going to Yamahas site and investigating how they identify their motors I believe it is a B90TLRV. I can read 6H1 and then the letter L. Everything else is missing.
Before I bought the boat, I did a compression check and checked the oil in the lower unit. Compression was 110, 111, 109 and 110. The boat had not run in 3 years so I pulled the carbs and thoroughly cleaned them. They were all spotless by the way. The previous owner put the boat up the right way. There was no gas in the tank and the carbs had been drained. Fresh fuel, fresh oil and a new battery and she fired right up. I put the boat in and noticed that the engine ran well up to half throttle or so, then rpms dropped, the engine seemed to smooth out and it ran ok right up to 5100 rpm. Backing down the throttle, the rpms dropped steadily then picked up just below half throttle. The engine sounded like it was running richer.
So back to the shop. I checked the fuel pump to make sure it wasn't dumping into the engine and it wasn't. Next, C]carbs off again. Disassembled, blown out, washed and really checked over. Back in the water and same thing. Now I am thinking timing. I ordered a factory service manual but it's not here and won't be for a couple of weeks. I'm going to throw my timing light on it tomorrow and see what the timing is.
Now my question. From what I've read here the full retard is 7 degrees atdc and full advance is 22 btdc? I see the CDI box has a potentiometer for the timing and maybe the pot is bad? Easy enough to check. I should probably turn off the enricher to see if that's my problem too. I should have put 12 volts to the coil to see if the plunger moved.
Oh, the book I ordered is for a '96 90v. Only one I could find so I hope it's the right one.
Before I bought the boat, I did a compression check and checked the oil in the lower unit. Compression was 110, 111, 109 and 110. The boat had not run in 3 years so I pulled the carbs and thoroughly cleaned them. They were all spotless by the way. The previous owner put the boat up the right way. There was no gas in the tank and the carbs had been drained. Fresh fuel, fresh oil and a new battery and she fired right up. I put the boat in and noticed that the engine ran well up to half throttle or so, then rpms dropped, the engine seemed to smooth out and it ran ok right up to 5100 rpm. Backing down the throttle, the rpms dropped steadily then picked up just below half throttle. The engine sounded like it was running richer.
So back to the shop. I checked the fuel pump to make sure it wasn't dumping into the engine and it wasn't. Next, C]carbs off again. Disassembled, blown out, washed and really checked over. Back in the water and same thing. Now I am thinking timing. I ordered a factory service manual but it's not here and won't be for a couple of weeks. I'm going to throw my timing light on it tomorrow and see what the timing is.
Now my question. From what I've read here the full retard is 7 degrees atdc and full advance is 22 btdc? I see the CDI box has a potentiometer for the timing and maybe the pot is bad? Easy enough to check. I should probably turn off the enricher to see if that's my problem too. I should have put 12 volts to the coil to see if the plunger moved.
Oh, the book I ordered is for a '96 90v. Only one I could find so I hope it's the right one.
Comment