Boat porpoising badly--can't get up to speed?--Help!

[sca101]

I'm looking at a classic 1962 Glasspar Citation. The boat itself is in great shape-very little work needed to get just right. Power is a problem. It has a Johnson 115 h.p. which is probably way too much motor for this boat. I couln't find a rating plate or online help with max rating. The owner left the boat to his nephew -who didn't use it. The owner has since passed away so I can't ask questions. I took the boat out for a lake test tonight. The motor started right up (after 4 years), and it idled and ran great out through the no-wake zone. Gave it some power and it bowed up badly. Gave it more power and it seemed to just backwash instead of forward thrust. Tried it gently and firmly several times, but could never get up any speed or even near plane. I'd say 7-10 miles an hour was as fast as I could get before the prop would wash and the r.p.m.'s go way up. No r.p.m meter on board. Motor felt as though the prop was always spinning--way too fast. It also has a happy troller/alluminum plate mounted behind/above the prop. It was in the up position, so I don't think that was the problem. I took off the prop to check for spun hub, but it looked O.K.. I really like the boat and could change the motor--the boat alone is worth the price, but I hate to buy it knowing I may need another motor--I'm not a boat mechanic. The boat did not seem to sit too low in the back, but nothing I tried got it going. It does not have tilt/trim. Motor was in the locked down position. Not sure what to do? Any advice would be appreciated. I thought I was coming home with an old classic in Great Shape tonight, but brought home frustration instead. Thanks

 

[jdlough]

Re: Boat porpoising badly--can't get up to speed?--Help!

Just some guesses...

It sounds like maybe the motor is mounted too high? So the prop is partially out of the water when you try to gun it?

Or maybe this boat was repowered with a too-short motor for resale? Like it needs a 25" shaft and it has a 20" shaft?

Or, more likely... You said it has no power tilt/trim. It sounds like it is trimmed out too far. That would force the bow up, and may also account for the prop wash out. See if you can reset the trim down to a lower pin setting (i.e. set it so the prop is tucked closer to the boat)

Or maybe it just needs Smart Tabs? (search here on iboats for plenty of "Smart Tabs" info).

Last dumb thought - If the lake was really shallow there, you could have just been just plowing through the mud bottom.

It sounds like the motor is mounted to high, or the trim is set too far out.

 

[cougar1985]

Re: Boat porpoising badly--can't get up to speed?--Help!

possible longshaft on short shaft boat?do you have pics of boat and motor?a fellow i know brought home a older glass boat this year and its rated for 80hp and its only 14feet long !did they even make a 115 in 62?

 

[VeroWing]

Re: Boat porpoising badly--can't get up to speed?--Help!

Check cavitation plate location. That is the flat plate on lower unit directly above the propeller. That should be even with the bottom of the hull, as a rule of thumb.

Also check angle of motor, compared to angle of boat. Are you sure that there is not an electric trim/tilt unit on midsection of outboard that may be in a slightly raised position.

If you could post a couple pics of outboard, we could get a better look.

 

[sca101]

Re: Boat porpoising badly--can't get up to speed?--Help!

possible longshaft on short shaft boat?do you have pics of boat and motor?a fellow i know brought home a older glass boat this year and its rated for 80hp and its only 14feet long !did they even make a 115 in 62?

The original motor has been replaced with a 1978 115 h.p. Johnson.


I just drove out and "actually looked" at the lower unit and motor positioning. The skeg has been ground down to about a 1/4 inch--obviously drug down the road a long ways sometime previously. Also the motor was set to the farthest out position away from the transom. It has 5 adjustment holes for the pin and it's in number 5--way too much angle. I assume the previous owner (now deceased) only went at very low speeds for trolling--I assume this only becasue it's set so far out and it has a happy troller installed. Will the skeg being gone severly impact my ability to ever have decent performance. I don't care how fast this boat will go, just that I can pull my kids skiing and go "pretty fast". Would the motor being adjusted all the way out cause me to "never" get the boat going--it just kept prop washing. I couldn't get over 7-10 miles an hour and the bow was way up, which I didn't like. I didn't actually look at the speedometer-I was too busy trying to adjust the throttle more and less to get the nose down. The motor "does not" have tilt or trim. Thanks

 

[Capt'n Chris]

Re: Boat porpoising badly--can't get up to speed?--Help!

Oftentimes you can't tell if a prop hub is slipping even by trying to to duplicate it by hand. That was a big little 16ft boat and 115 is too much motor, even if it ran well. I would think a 60 or maybe a 75 would have been proper for it. Regardless, if the motor "wrapped up" like you describe, change props with one you know is good if you are so inclined. Make sure that the pitch is great enough that it wouldn't cause the motor to over rev. Someone might have put a prop on designed to push something big and outlandish. If so, it will rev as described. That's where this old salt would start. So, how was it porpoising badly?

 

[Silvertip]

Re: Boat porpoising badly--can't get up to speed?--Help!

Get rid of the trolling plate. Trim the motor in as far as it will go. Answer the question about the position of the AV plate (with the motor trimmed properly). I also agree that this is probably a long shaft motor on a short shaft boat. That alone regardless of trim setting will cause extreme bow lift due to the added leverage of the long shaft motor. That would also account for why the motor was trimmed out so far. Check for a spun hub by making a mark on the blade area of the prop. Then make another mark directly in line with the first, but on the hub. Then run the motor until this washout, blowout, or whatever you call it occurs. Then check the marks. If they are still lined up the prop is NOT spun. If they are no longer aligned, the prop hub has indeed spun.

 

[sca101]

Re: Boat porpoising badly--can't get up to speed?--Help!

Problem fixed--turns out I was in a hurry and should have paid better attention. After moving the motor adjustment pin from the farthest "out" position to the closest "in" position (moved from 5th hole down to 1st hole) the boat now works--better than I'd ever hoped! It now screams out of the hole and barely came up at the bow. I was always able to see water. Went too fast in fact with no prop wash. The shaft lenght is correct as the cavitation plate is even with the hull bottom. I think I need to try to sell this motor and get one about 1/2 the size. This is "way too much" power for this boat. It's a 1962 Glasspar that probably weighs about 600 lbs. They didn't put passenger or horsepower ratings on the boat back then--was probably in the catalog/brochure, but not on a plate in the boat, but I'm willing to guess recommended H.P. is 50-60 at most. I don't need to go over 50 m.p.h., but boy did it run fast--out of the hole and top speed! Thanks for your help.

 

[woosterken]

Re: Boat porpoising badly--can't get up to speed?--Help!

Sca.,
check this out............. more info for you

http://www.clubmarine.com.au/internet/clubmarine.nsf/docs/MG19-2+Technical

woosterken