No Speed-gctid378434

[Guest]

I took my boat out for the first time in decent weather and was disappointed in the performance. She's a 3218 with 305's, at full throttle I could only get 3000 RPMs at about 10 knots! The engines seem to be running good. They run smooth and sound good. But I'm sure the performance should be better! Any help?

[Guest]

What should the prop size be for this boat? I'm not sure about the size that is on it, but I have a set of spare props that are 3-blade 16 dia; 14 Pitch. I was looking on the internet and saw a 3270 for sale and said it had 4-blade 17x17 props! Big difference!

[Guest]

Nobody?
..........

[Guest]

Are the props clean? Is the bottom clean? Is the running gear clean?

On my boat, marine growth on those things KILLS performance.

[Guest]

Had the bottom done 3 months ago. Looked under with a mask, all still looks good.

[Download_Complete]

Time for a full tuneup on both engines, check timing, check carbs, check fuel pumps, etc.

[Guest]

I agree with the tune up, you have motors with points and they need to be replaced yearly and adjusted correctly to perform at their peak. A set of plugs would help out too....

[Guest]

Alright, thank you. I had it tuned when the bottom was done but I'll have it checked out. Anyone know about the prop size?

[Guest]

The other thing that has hurt my top end is from a poor design feature on my Mercruiser 454 MAG Horizon engine.

On my engine, the fuel pressure regulator is controlled by manifold vacuum. They tapped off manifold vacuum w/ a nipple off the bottom of the intake pleneum onto a downward hose to the fuel pressure regulator.

There have been several instances where a small amount of oil obstructed functionality on that vacuum line, preventing the fuel pressure regulator operation.

Normal operation was restored by cleaning.

[Guest]

Pappy-

I have an 86' 3270 and replaced my props last year. Same motors as you - 305's with the MS3C transmissions. Went with Michigan Wheel DJX 16x14 with a #4 cup. I couldn't be happier. WOT is about 4800 and top speed is close to 20 knots. I generally cruise at 3500 about 12-15 knots.

Mark

[Guest]

Thanks J4F, that's what I have 16X14.... maybe the engines aren't running as good as the sound! But I could only get 3000 RPM at about 10 knots!

[2850Bounty]

All of your Ducks must be in a row before you can proceed.

Full engine tune (this means everything), including a test to see what the progressive ignition advance is doing.

Many mechanics will omit this portion, and will set BASE advance ONLY......, and go on their merry way.

Only then can we perform a WOT RPM test to see if it is propped correctly.

Anything other than this, may be a waste of your time and money!

.

[smitty477]

"Had the bottom done 3 months ago. Looked under with a mask, all still looks good"

FWIW - 3 months here and we would not be bale to get on plane at all. The stuff grows on the running gear and props much faster then on any bottom painted surfaces.

I am not sure what you mean by 'Looked under with a mask' but please be sure the props/running gear is clean before proceeding with anything else.

Seriously be sure that is not the culprit.

Hope this helps

[2850Bounty]

smitty477 wrote:
Seriously be sure that is not the culprit.

Agreed.... that's part of the "ducks" that I'm refering to.

.

[Guest]

Understood, thanks guys! I'll have a mechanic check it out throughly.