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Boat won't plane.

Posted: August 19th, 2019, 8:45 am
by Craig_B
Recently purchased a 1988 Santego this spring.
When we had it out for its sea trial the operator managed to get the boat up on plane but he did have to fiddle with some of the controls to suceed.

I have not had any luck. At first I thought I could not get it on plane due to the trim tabs being stuck in the down position.
Fixed that and they are both now fully retracted.
Went out last weekend to try and sort it out but got chased off the lake due to an incoming squall.
I had the tabs up and the drives all the way down/in.

Any input on what is wrong or what I am doing wrong. Not at all familiar with a boat this size or dual engines.

The boat has twin 5.7 Mercruisers with Alfa One stern drives.
Engine RPMs reached approx. 3000 and no more.

Cruises along at a nice efficient 7 knots @ 1500 RPM but at full throttle managed to just reach 9.7 knots.

I don't mind cruising at 7 but would like more speed when its necessary and I figure this non plane issue is a sign if something else out of whack.

Thanks

Re: Boat won't plane.

Posted: August 19th, 2019, 10:02 am
by bud37
Craig, do you remember what rpm you achieved on the sea trial ? Seems if the guy had to fiddle to get it on plane with the tabs stuck down then you should be able to do it now unless the boat got heavier......you could have been just at the tipping point on the sea trial.That 3000 you are seeing is just about the point the boat should pop up,....are both throttles full at this point ?

There are many reasons for this from wrong props ( over propped ), advance in distributors sticking on both or just one engine, fuel issues from bad gas, filters to pumps, dirty bottom.

Do you have an engine sync gage on the dash, if so how does it react when trying to get it on step ?

Re: Boat won't plane.

Posted: August 19th, 2019, 10:41 am
by Craig_B
I can get a higher rpm on the starboard engine both levers fully forward.
Port engine tops out at 3000 can get more on starboard but I was trying to keep them even.
I don't think the tabs where stuck down on the trial. It was just low on fluid.
If i remember correctly he had the rpms higher, maybe 3400-3500 rpm?

Do I have the drives/tabs in the correct position to plane or should I tilt the drives up a bit?
I will pull the distributer caps and see the advance is seized.
I also noticed the port engine heated up more than the starboard when under full throttle.

Thanks

Re: Boat won't plane.

Posted: August 19th, 2019, 10:45 am
by Craig_B
bud37 wrote:......you could have been just at the tipping point on the sea trial.That 3000 you are seeing is just about the point the boat should pop up,...


How long does it normally take to go from pushing a big bow wave to getting on plane? Maybe I am just not pushing long enough.

Re: Boat won't plane.

Posted: August 19th, 2019, 10:51 am
by bud37
Craig, before you do any more, check the timing and advance....what you are seeing could be the port engine struggling therefore it will hold the other back.......So my advice is to have a close look at that and fuel filters etc.........Don't beat on it till you sort this out.
The extra temp can be a result of timing in some cases. Like I said before and I am sure others will agree there are many things to cross off but one thing at a time.

Do you have the sync gage ?

Re: Boat won't plane.

Posted: August 19th, 2019, 11:27 am
by Cooler
One more thing could be stretched, worn out, control cables. Those cables would only be around $50 plus install. Or, maybe the port needs to be adjusted. 8-) er

Re: Boat won't plane.

Posted: August 19th, 2019, 11:54 am
by Craig_B
Yes it has a sync gauge. It shows more power to starboard. So I was pulling back to make them even.

Re: Boat won't plane.

Posted: August 19th, 2019, 12:04 pm
by km1125
Craig_B wrote:Source of the post
bud37 wrote:......you could have been just at the tipping point on the sea trial.That 3000 you are seeing is just about the point the boat should pop up,...


How long does it normally take to go from pushing a big bow wave to getting on plane? Maybe I am just not pushing long enough.

Depend on how hard I mash the throttles. If I pushed them all the way, then it's 4-5 seconds and I'm up on top planing and increasing speed. If I only push them to my cruising speed (~17-18MPH) then it takes about 10 seconds before I'm up and planing and a little bit longer to reach cruising speed.

If you mash the throttle and the port engine stops increasing at 3000 rpm, then you need to find and fix that issue. Timing and fuel restrictions (dirty filters) are your more likely causes, but as Cooler says, make sure the engine are actually opening fully on the throttles before you get too far looking into anything else.

Re: Boat won't plane.

Posted: August 19th, 2019, 12:05 pm
by bud37
Craig_B wrote:Source of the post Yes it has a sync gauge. It shows more power to starboard. So I was pulling back to make them even.

So you pulled the stbd engine back to get the sync gage in the middle is that correct.??

Also what carbs do you have.....quads have a power valve affair that can be a problem and stick.

I agree with the above about the carbs maybe not fully open, easy check there.

Re: Boat won't plane.

Posted: August 19th, 2019, 12:44 pm
by Craig_B
bud37 wrote:Source of the post
Craig_B wrote:Source of the post Yes it has a sync gauge. It shows more power to starboard. So I was pulling back to make them even.

So you pulled the stbd engine back to get the sync gage in the middle is that correct.??

Also what carbs do you have.....quads have a power valve affair that can be a problem and stick.

I agree with the above about the carbs maybe not fully open, easy check there.


Yes pulled back on SB throttle to keep engines even.
So it sounds like I need higher RPM to get up on plane.
Now to figure out with all the suggestions above how to get more RPM.

Thanks to all