Is this normal for the engine

[gustafsonerik]

85hp 87 force with a 17 foot bayliner..compression is 120 100 115 i can go about 28 mph in it should it go any faster with just carrying me 200lbs thanks Erik

 

[john from md]

Re: Is this normal for the engine

You need to decarbonize the engine and then check compression again. It should be at 140-150 range. WOT should give you 38-40 MPH at 5500RPM.

With those compression readings, you either have serious carbon build up or a leaking head gasket. Try decarbonizing first as it is easy and cheap to do. The procedure is listed in the faq.

Regards,

John

 

[Frank Acampora]

Re: Is this normal for the engine

Well, I had an 85 on an 18 foot Renken deep vee and it went about 28-30. So, on the 17 footer I would expect a little more.

But the reality is that there are so many variables from hull condition to engine condition to--most important--correct prop, that it is difficult to predict speed.

First thing I would do is to be sure that the prop is in good condition with no major bends or nicks in the blades. Then if at all possible, I would try different pitched props. If you have too much pitch, it will bog down the engine and not let it develop its maximum horsepower thus speed will be lower than expected. Optimize your running trim and be sure the engine is not mounted too low on the transom. Running with trim tucked in toward the transom too far will have too much hull in contact with the water and will knock off at least 5 mph.

I suspect that with that set up you would want to use a 13 X 17 pitch prop to start. And if you have the stock black open hub prop, you will gain some speed just by changing it to a better one.