Slow Start Under Power

[Cool_Change]

Have a 1981 h27 with 1GMH Yanmar and fixed 2 blade prop...When first getting underway under power it seems to take forever to pick up any speed although once going will run at about 6 knots no problem. I realize that it takes a bit to gather momentum but when I watch other boats they just seem to have a lot more a lot sooner!Any thoughts / suggestions? Would a 3 bladed prop make a significant difference and is it ok for this boat? I'm assuming that the current one is original...Scott

 

[Alan]

A Few Thoughts

#1 How clean is your bottom? A dirty bottom that isn't smooth and clean is sacrificing a great deal of efficiency to drag. #2 How clean is your prop? Same thing as #1. A dirty prop is very inefficient. Are you able to rev the engine? Does it hit its max RPMs without black smoke belching out he exhaust?

 

[Cool_Change]

I went for a swim...

...just yesterday to check this. A bit of algae on the rudder where it gets some sun but other than that pretty clean and was new anti-fouling in the spring. Prop is a bit pitted (age I assume) but clear of any growth etc.Engine seems to rev fine...only time I get bit of smoke is upon shutting it down. I rev it for a few seconds to max to blow out the cylinder, it smokes a bit there and then idle and pull the stop.

 

[Karl]

slow boat

A few things:The engine is a bit small for the boat...it really should have been a 2 cylinder in a 27' boat. This is your basic problem.The condition of boat bottom and the edges of the prop are important to start up and speed. Smooth and clean is best.Definately not a 3 blade prop it would only make things worse.Finally, if the engine doesn't reach it's full rpm under load (not in neutral) check the air cleaner and the exhaust elbow and the throttle linkage.

 

[Cool_Change]

2 vs 3 blade - why?

Thanks for the tips...Seems to be a common observation that the h27's need more than the 1GMH puts out!The engine does reach full revs under power and other than a slight hesitation at about the halfway point in going from idle to full (is this normal?) seems to run fine. As well, once up to speed pushes the boat fine...the delay is in getting it there which for the most part really only concerns me in close quarters from a control perspective.Other than 1 blade...what is the difference between using a 2 vs a 3 blade prop? I would have expected a 3 blade to provide more bite in the water and hence better low end power...why would going with a 3 be worse??Scott