A little help?

boater · **Posted:** Fri Jul 13, 2012 10:26 am

The boat was running great when it first went in.
The last couple times out, it didn't seem right.
Not much power and not going as fast as it sounded like we should be. I took it out last night and got up to 35mph at 4000 rpm.
When it first went in it was 55 at 4500 rpm.
The motor sounds right, like it's trying, just not getting to the prop.
Could low drive oil do this? Do you think it's something worse?
It's in the water and doesn't have an unusual amount of growth on it.
Thanks!

alanurt · **Posted:** Fri Jul 13, 2012 12:03 pm

Is it bottom painted? You'd be surprised how little growth can affect performance. It could be a compression issue, but I would clean it of all growth first and try it out.

ric · **Posted:** Fri Jul 13, 2012 12:58 pm

did u ding the prop? check it out

boater · **Posted:** Fri Jul 13, 2012 2:24 pm

No bottom paint. It's been kept in the water every year since new and never had this problem.

Prop is fine. I looked at it last night.

alanurt · **Posted:** Fri Jul 13, 2012 5:23 pm

Serious?! I'm assuming salt water. If so, take it out and clean it. You should be cleaning it every two weeks if you aren't going to paint it. I have no experience with fresh water.

boater · **Posted:** Fri Jul 13, 2012 5:49 pm

I'm in fresh water and I do clean it.
No barnacles or anything. :wink:

alanurt · **Posted:** Fri Jul 13, 2012 5:52 pm

Well, I'm not a big motorhead, but I would start with a compression check. Motor may be tired.

boater · **Posted:** Fri Jul 13, 2012 7:07 pm

Thanks for the suggestions. I'm going to go take the prop off tomorrow and make sure
I didn't get something tangled up in it. I don't know if that would be it or not.
Then I'm calling my friend/mechanic. The boat's going on a 2 week vacation with us in
a couple weeks, so I need this figured out!

Waked Up · **Posted:** Fri Jul 13, 2012 8:46 pm

I would pull the fuel bowls off of the carb, and check the fuel filter, for sediment/ flow, pull 2- plugs(opposite ends of the block on opposite sides)...when did you change them last?, and what kind do you run?, check the distributor to make sure the locking bolt has'nt loosened and caused a timing issue. Further check the feel of the shift mechanism for resistance if it feels smooth and moves equal distances between forward, and reverse then it should be OK. Test the plug wires, if you don't have a tester, and you have a lazer temp gauge then warm it up and test all the exhaust ports for temperature look for cold ports, if you don't have a gauge then pull the wires one at at a time and when removing a wire doesn't change the way it runs you found the bad plug. If these tests are all good spray the intake gasket surfaces with a flamable liquid like WD-40 lightly around the gasket surfaces if the RPM increases you have a vacuum leak....correct it(keep fire extinguisher handy). Chek all fluid levels, including outdrive, change if blackness is apparent, and if you still haven't solved it then start with the compression check.

boater · **Posted:** Fri Jul 13, 2012 9:51 pm

I was thinking bad plug at first, but if I'm getting 4000 rpm's even running poorly
I should be in the mid 40 mph range. Plugs and wires were new last year. Whatever plug Volvo recommended.
It starts right up and idles perfect and runs perfect until I'm on plane. Speeds are all screwed up.
At 3000 rpm I'm barely in the 20's, but it sounds like I should be going 30.
It doesn't miss or act strange, it's just slow.
Shifter is smooth like it's always been.
I'll check all that stuff out in the morning. I doubt I'll be spraying flammable liquid though!
I do have a laser temp gauge.
And before someone asks, I've been using 91octane non-ethanol fuel all year.
( that's probably my problem

)

Waked Up · **Posted:** Fri Jul 13, 2012 10:26 pm

You don't have to spray flamable liquid you can do the opposite and spray water an look for a stumbling condition(just more responsive & obivious with the WD-40). How old is your prop and is it aluminum or SS. Age of the plugs and wires is not representitive of their condition or functionality, just a guideline of necessary maintenance requirements, use the lazer gauge the test is telling. Are you using the speedo, is the wheel functioning properly, or are you verifying with a GPS unit. Do not forget the carb, and the float bowls, the are integral parts of the system and MUST function properly to build torque, and horsepower. Take the time and do the checks, if it passes then move on if it doesn't than fix it and test it. The aluminum props can become soft, increasing slippage. If the motor is revving correctly to peak HP then traction or transfer is likely the cause of the transfer loss, a soft/flexible prop will cause traction loss, not too common with the SS. Does the engine rev higher in neutral than it does under load. Electrical has not been mentioned yet but a poor ground on the battery can also cause the engine not to reach max RPM.

flaMtneer · **Posted:** Sat Jul 14, 2012 8:32 am

Just to state the obvious - Have you checked your gauges? I assume you're using GPS for speed? I had a similar issue a while back and I was baffled. I was having to run 500-1000 RPM higher than normal to get speeds. This was very consistent over a couple days. Then while idling I looked at the RPM gauge and it was on 4000 - tapped on it and it dropped back to normal...throttled up to 3500 RPM at 30 mph, tapped gauge and it dropped back to 3000 like normal.

boater · **Posted:** Sat Jul 14, 2012 10:38 am

Speed was all with gps. I had a stainless 3-blade 21p on.
So I went over this morning to check things out. I took the prop off to make sure nothing was tangled up.
Nothing there, so I put my old 4-blade 19p aluminum prop on and went for a ride. Ran like new.
I just got the stainless at the beginning of the season. It's a Stiletto. So what happened? Is that what a spun prop does?
Never happened to me before.
I do have to tap my tach once in a while also.

alanurt · **Posted:** Sat Jul 14, 2012 10:54 am

Great news. I'm a little surprised you got up on plane with a spun prop, but glad that's all it was. Funny, I also had to tap my tach on occasion.

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