70hp Force 1992 Bayliner Capri 1700

[1992 Bayliner Capri]

Hello,

We just bought a 1992 Bayliner Capri with a Force 70 on it from a guy who told us the boat had nothing wrong with it. He started it in the driveway and it fired right up. So after we bought it we took it to the lake and ran it wide open and the boat only registered 20mph on the dash. My question is shouldn't a 70hp engine be able to push a 17' fiberglass boat faster than 20mph on the lake? We previously had a 70 Yamaha on a 15' Fiberking Bomber and it would do 40mph on the water easy. Please offer any insight....

thanks,
Lee

 

[NYBo]

Re: 70hp Force 1992 Bayliner Capri 1700

Welcome to iboats!:welcome:

How were you measuring speed? Pitot-based speedometers are notoriously inaccurate. GPS is a better bet. Also, do you have a tachometer? If so, what is the motor speed at wide open throttle? If it's in the4 proper range for the motor, you have prop issues (wrong pitch, spun hub).

 

[jerryjerry05]

Re: 70hp Force 1992 Bayliner Capri 1700

You can usually tell if your going 10 or 30 did it seem like the speedo was right?
The motor over revving?
Do a compression,spark test.
Like NYBo suggested. A GPS on a phone.

 

[DAN M VAGOS]

Re: 70hp Force 1992 Bayliner Capri 1700

You need a gps or tac Iwas using a free gps app on my iphone that worked great.

 

[Frank Acampora]

Re: 70hp Force 1992 Bayliner Capri 1700

Comparing your Yammi on a 15 foot hull to the Force on a 17 foot hull is like comparing apples to oranges. You just can't do it. Different hull/engine combinations will perform differently. At any rate, I would not expect much more than 28 with that Force/Bayliner combo.

Aside from that, the Force 70 uses a 10 inch diameter prop and unless lightly loaded, I would suspect that it would have a lot of prop slip.

If you were measuring speed with the dashboard speedometer, was the pitot tube at the transom all the way down? What pitch is the prop? What RPM was the engine turning at full throttle? An over pitched prop on a 17 footer will lug the engine and reduce top speed.

 

[1992 Bayliner Capri]

Re: 70hp Force 1992 Bayliner Capri 1700

You can usually tell if your going 10 or 30 did it seem like the speedo was right?
The motor over revving?
Do a compression,spark test.
Like NYBo suggested. A GPS on a phone.

Speedo seemed right, I mean we was being passed by Pontoon boats with 50hp engines on them. The engine to me sounded like it wasn't opened up all the way. I have no idea how to do either one of those tests you mentioned. We do not get phone signal anywhere on Nolin Lake so will a GPS on a phone work?

 

[1992 Bayliner Capri]

Re: 70hp Force 1992 Bayliner Capri 1700

Welcome to iboats!:welcome:

How were you measuring speed? Pitot-based speedometers are notoriously inaccurate. GPS is a better bet. Also, do you have a tachometer? If so, what is the motor speed at wide open throttle? If it's in the4 proper range for the motor, you have prop issues (wrong pitch, spun hub).

Measuring speed by the speedometer on the dash. There is not a tachometer wired into the boat. I tried getting the numbers off of the outside of the prop but I cant make them out. I forgot to mention that the boat burned up 5.5 gallons of gas within 30 minutes on the water. That doesn't seem normal to me.

 

[1992 Bayliner Capri]

Re: 70hp Force 1992 Bayliner Capri 1700

Comparing your Yammi on a 15 foot hull to the Force on a 17 foot hull is like comparing apples to oranges. You just can't do it. Different hull/engine combinations will perform differently. At any rate, I would not expect much more than 28 with that Force/Bayliner combo.

Aside from that, the Force 70 uses a 10 inch diameter prop and unless lightly loaded, I would suspect that it would have a lot of prop slip.

If you were measuring speed with the dashboard speedometer, was the pitot tube at the transom all the way down? What pitch is the prop? What RPM was the engine turning at full throttle? An over pitched prop on a 17 footer will lug the engine and reduce top speed.

I am having trouble making out the numbers on the prop. Is there a way to tell the pitch other than on the outside of the prop? I have no idea as to what rpm's it was spinning at since there is only a speedometer on the dash. What do you mean by prop slip?

 

[roscoe]

Re: 70hp Force 1992 Bayliner Capri 1700

You will need to do some investigating and narrow things down to diagnose.

Start with a spark and compression test.

Check the sparkplugs after running the motor for 15 minutes.
Do they look the same? Is one cleaner than the other 2?

Open the fuel pump and inspect the diaphragm, looking for holes or tears.
Could be it is damaged, which would flood the crankcase and lower cylinder, causing it not to fire, and dumping lots of fuel out the exhaust.

THat motor should only be using 6 gallons per hour at full throttle.