98 Johnson 50 with RPM trouble

[miknmic]

I have a 98 johnson 50 on a 26 foot pontoon<br />and it does not go over 3000 rpm's. I have done the following.<br />1)Changed the plugs 2)Changed the fuel filter<br />3)put heat in the tank 4)shot a can of OMC tune up in it 5)I found out that the moron at the factory did not take the plastic plug out of the vent fitting.<br />When the boat is running the bulb goes soft and under power when you pump it does not make a difference. It does reach high rpm in nuetral. It does run good at 3000 rpms it just takes a little longer to get to the sandbar.

 

[hondon]

Re: 98 Johnson 50 with RPM trouble

How are you propped? With this package I would expect you to be in the 9 or 10 inch pitch range.It is possible that running an unvented fuel tank may have stressed your fuel pump diaphram but ulikely since it won't pick up with the squeeze of your primer bulb. Might consider elimnating the anti siphon valve.

 

[hondon]

Re: 98 Johnson 50 with RPM trouble

Also to keep it really simple check to see that your carbs are opening fully.On the starboard/right side of your engine ,look at the carbs. On that side you will see a little roll pin on the shaft that pivots when you move the throttle. When you move the throttle that roll pin should move from almost horizontal to vertical,not quite 90 degrees since you didnt start out completly horiz.,but it should be staight up and down. If not your carbs are not opening fully.

 

[Down South]

Re: 98 Johnson 50 with RPM trouble

Has the motor ever turned more rpm than 3000 on this pontoon boat? (If not)It takes a lot of power to move one of these things. Problem is the rear framework of the boat drags in the water and it really can bog a motor down. If the rpm has always been this low since you had it, I would check the prop pitch.<br /> I have a 24 ft pontoon boat with a 90 HP Mercury and the best I can do with it is about 5200 rpm.