How Fast Should my boat go

[eavdic]

Hi I have a 1991 Bayliner Capri Bowrider with 70 HP outboard Force. I have played around with tilt and top speed I can get is 32 MPH. Does this sound right? Motor works fine. Also does anyone know what the compression should be on these. I know they should be 15 within each other but what should it be. Thank you .

 

[1983rinker]

Re: How Fast Should my boat go

32 is very good and abought right. 130/140 psi

 

[eavdic]

Re: How Fast Should my boat go

will re-de the compression check thank you very much.

 

[coolbikeguy]

Re: How Fast Should my boat go

i agree ... 32 out of a 70hp on that boat is good. you should be happy with that.

 

[jerryjerry05]

Re: How Fast Should my boat go

Compression should be even.Different guages=different readings.
My guage cost $100 and it gives the correct readings.Cheaper guages will give poor results.
Speed??? You have a tach?Top speed is acurate when you have optimum performance.That motor should do about 5500rpm at WOT.
1-2 people 1 kid or big dog.1/2 tank and small cooler.A little more or a little less is OK. but a lot of difference is a problem.
Do a test and post your results(good or bad) J

 

[eavdic]

Re: How Fast Should my boat go

I do not have tach , I used my garmin to measure speed , but not sure about RPM, I am thinking about getting a tach installed to see what the rpm are. I will do the compression check again and will post.

 

[BuzzStPoint]

Re: How Fast Should my boat go

Out of an older engine.. Knowing the precise compression isn't needed. The main thing you want to look at is when you do the compression, the readings between cylinders should be no more then 5-10 % difference.

 

[eavdic]

Re: How Fast Should my boat go

Compression should be even.Different guages=different readings.
My guage cost $100 and it gives the correct readings.Cheaper guages will give poor results.
Speed??? You have a tach?Top speed is acurate when you have optimum performance.That motor should do about 5500rpm at WOT.
1-2 people 1 kid or big dog.1/2 tank and small cooler.A little more or a little less is OK. but a lot of difference is a problem.
Do a test and post your results(good or bad) J

I have installed a tach, at idle it runs at 1000 RPM at trolling it runs at 2500 RPM and at WOT it runs at 4500 RPM never reaches 5500 RPM like you said do you think the engine needs to be adjusted somewhere so that it can go more RPM.?

 

[eavdic]

Re: How Fast Should my boat go

Out of an older engine.. Knowing the precise compression isn't needed. The main thing you want to look at is when you do the compression, the readings between cylinders should be no more then 5-10 % difference.

will a diffrent prop give me more speed?

 

[jerryjerry05]

Re: How Fast Should my boat go

If the tach is right you can re-prop with a lower pitch.From a 19 to a 17(what do you have?)
Still do a comp test before you change anything.J

 

[eavdic]

Re: How Fast Should my boat go

If the tach is right you can re-prop with a lower pitch.From a 19 to a 17(what do you have?)
Still do a comp test before you change anything.J

I have a 10.38x14 pitch prop, my compression is at 100 PSI across all 3 cylinders, rpms are at 4900 but they should be at 5500. any suggestions

 

[jerryjerry05]

Re: How Fast Should my boat go

There is a section for props.Some good guys over there.You might go with a smaller prop.But ask there first.
Take the info you have and try there.J

 

[blueoval78]

Re: How Fast Should my boat go

I have a Capri 1500 with a Force 50hp and have been experimenting with props. I had a 10 - 3/8 x 13.5 and could do 28 MPH by myself in the boat; at 4500 RPM's. WOT is 4500 to 5500 for my motor so I figured if I dropped to a 11.5 I would be more in my sweet spot and gain speed. Switching the prop actually dropped me down to 25 MPH at 5000 RPM's.

I would suggest staying with your current prop if speed is what you are looking for.

 

[eavdic]

Re: How Fast Should my boat go

Oh wow, thank you for letting me know. I get 33 mph confirmed with GPS with this prop but my rpm are around 4900. Prop is almost brand new, for now I guess I will leave as is and in case if I need a new prop I will go with that one.

 

[Desertsky]

Re: How Fast Should my boat go

I have a Capri 1500 with a Force 50hp and have been experimenting with props. I had a 10 - 3/8 x 13.5 and could do 28 MPH by myself in the boat; at 4500 RPM's. WOT is 4500 to 5500 for my motor so I figured if I dropped to a 11.5 I would be more in my sweet spot and gain speed. Switching the prop actually dropped me down to 25 MPH at 5000 RPM's.

I would suggest staying with your current prop if speed is what you are looking for.

Wow, that sounds pretty good! I have a Capri 1400 with the Force 50 and I can only get 24mph with me and wife in it. Of course, that is at 8600ft elevation!

 

[eavdic]

Re: How Fast Should my boat go

well I have 70HP Force