LOW REVS

[leafs]

1974 TRIHULL WITH 1974 JOHNSON 70HP<br />RUNS GOOD .EXCEPT WHEN YOU GIVE IT FULL THROTTLE,THE REVS ONLY GO SO HIGH,AND THE BACK OF THE BOAT STAYS DOWN,AND IT SOUNDS LIKE THE MOTOR IS BOGGING DOWN ,FRONT END WAY UP.COMPRESSION IS ALL AROUND 125. EVERY TIME I START THE BOAT I HAVE TO USE THE CHOKE EVEN WHEN MOTOR IS WARM. THE FIRST TIME I TOOK THE BOAT OUT IT SEEM TO WORK FINE UNTILL I DROVE THROW SOME MUD AND WEEDS<br />THATS WHEN IT FIRST SEEM TO BOGG DOWN, AND THE FRONT OF THE BOAT WOULD NO LONGER GO DOWN.ANY IDEAS

 

[Bob_VT]

Re: LOW REVS

Good morning leafs. Please don't use all capitols it is considered to be shouting <br /><br />A bit more info on your setup will be helpful. Is the boat stored "in the water" or trailered?<br /><br />If it is stored in the water I would suspect bottom fouling. If the boat is trailered I would suspect a weight gain from water in the hull. Both would lead to lack of planing.<br /><br />Having to use the choke when the motor is warm is a slight indicator thet your motor may need to have the carbs cleaned.<br /><br />Check your prop for any recent damage too.<br /><br />Let us know.<br /><br />Bob

 

[jamesrose]

Re: LOW REVS

Hi Leafs. Just check that the prop spline isn't rotating (stiffly) inside the propellor boss. Modern props have a rubber interface between shaft and prop, which will shear easily in mud even if the shear-pin doesn't break. Result is full engine revs and half prop revs! james Rose

 

[leafs]

Re: LOW REVS

Thank you for the replys. The boat is fiberglass.<br />Could you please explain to me what is fouling and the boat is stored on the trailer.<br />How could I check for weight gain on the back of the boat and also how do I check the prop spline

 

[Spidybot]

Re: LOW REVS

Fouling is stuff growing on the bottom. Occurs only in the uppermost water as it needs light to life. Looks like green smear at first, grass or moss later on and like seaweed in the end.<br /><br />Normally prevented by applying botoompaint - so called antifouling.<br /><br />When your boat is on the trailer (which should be in balance so that the tongue weights approx. 100 lbs), you should be able to hear water moving insede the hull when you raise and lower the tongue (if the water is in a room where it can move). If the room is filled with foam and the water has swamped it, you cannot hear it.<br /><br />Another way is to get the boat+trailer+motor weight and calculate how much of this stems from the boat. Compare to the factory to know if you're carrying extra...

 

[leafs]

Re: LOW REVS

The bottom of the boat seems fine,and I dont't think there is water lying in the bottom of the boat.

 

[Spidybot]

Re: LOW REVS

OK. <br />Now we start thinking about fuel supply and ignition timing.<br /><br />Is there any way you can make the engine rev. higher than what it does when sailing? Try adding throttle (SHORT periodes) when in neutral?